OS21C-1242 0800h
An Experiment of Ocean State Estimate by Using Argo Data and a 4D-VAR Data Assimilation System
The in-situ Argo data is assimilated into a 4-dimensional variational data assimilation system in order to investigate its effects on the estimation of the ocean state. A time-varying oceanic reanalysis dataset is obtained which is dynamically consistent with both the ocean circulation model and the field observation. The assimilation result exhibits more realistic features of the ocean circulation processes than that obtained only from the ocean circulation model, showing the effectiveness of our assimilation model and the great impact of the Argo data. The 4D-VAR data assimilation system used in this study is constituted on the basis of a strong constraint formalism by using the GFDL Modular Ocean Model (MOM3) and its adjoint, as well as the 4-dimensional variational method. An optimization problem is solved to minimize the cost of the model result and the observational data by controlling the initial condition of the model variables and the air-sea heat, fresh water and momentum fluxes. In the experiment, only the Argo data of temperature and salinity profiles from Jan. 2001 to Jun. 2004 is used. A finer global model is selected in which the horizontal resolution is 1 degree in both longitude and latitude, with 36 vertical levels spaced from 10m near the sea surface to 400m at the bottom. Using climatological monthly forcing, a stable ocean state is firstly calculated. Then, a first guessed field is generated through a 24-year integration with NCEP2's monthly forcing started from 1980. Finally, the Argo data assimilation is carried out. It is revealed that both seasonal and interannual variations in the ocean state are significantly improved through the assimilation, although the coverage of Argo float is still very sparse. Phenomenon such as the El Nino event of 2002 is well reproduced by the assimilation, which agrees with the results derived from the objective analysis with Argo float and TRITON buoy data. To get more realistic estimation of the ocean state, other ocean observational data should be included into the assimilation model.
OS21C-1243 0800h
Optimal Spectral Decomposition (OSD) for Analyzing Sparse and Noisy Ocean Data
Great advantages of optimal spectral decomposition (OSD) in analyzing sparse and noisy ocean data are demonstrated in this paper. Two-scalar (toroidal and poloidal) spectral representation is used to reconstruct three-dimensional ocean flow from noisy data in an open domain. This approach includes: (a) a boundary extension method to determine normal and tangential velocities at an open boundary, (b) establishment of homogeneous open boundary conditions for the two potentials with a spatially varying coefficient ^, (c) spectral expansion of ^, (d) calculation of basis functions for each of the scalar potentials, and (e) determination of coefficients in the spectral decomposition of both velocity and ^ using linear or nonlinear regressions. The basis functions are the eigenfunctions of the Laplacian operator with homogeneous mixed boundary conditions and depend upon the spatially varying parameter ^ at the open boundary. A cost function used for poor data statistics is introduced to determine the optimal number of basis functions. An optimization scheme with iteration and regularization is proposed to obtain unique and stable solutions. The capability of the method is demonstrated through analyzing noisy and sparse Eulerian and Lagrangian data. References Chu, P.C., L.M. Ivanov, T.P. Korzhova, T.M. Margolina, and O.M. Melnichenko, 2003a: Analysis of sparse and noisy ocean current data using flow decomposition. Part 1: Theory. Journal of Atmospheric and Oceanic Technology, 20 (4), 478-491. Chu, P.C., L.M. Ivanov, T.P. Korzhova, T.M. Margolina, and O.M. Melnichenko, 2003b: Analysis of sparse and noisy ocean current data using flow decomposition. Part 2: Application to Eulerian and Lagrangian data. Journal of Atmospheric and Oceanic Technology, 20 (4), 492-512.
http://www.oc.nps.navy.mil/~chu
OS21C-1244 0800h
The Underway CTD
The development of the Underway CTD (UCTD) is motivated by the desire for inexpensive profiles of temperature and salinity from underway vessels, including volunteer observing ships (VOS) and research vessels. The UCTD operates under the same principle as expendable probes. By spooling tether line both from the probe and a winch aboard ship, the velocity of the line through the water is zero, line drag is negligible and the probe can get arbitrarily deep. The challenge is to recover the probe, because the line velocity will then equal the ship speed, and line drag may become large. This has proven possible using a Spectra line commercially available for fishing. A number of advantages accrue because the UCTD is recovered rather than expendable. First, the cost per profile decreases as the probe is reused. Second, because the probe is recovered, sensors can be calibrated post-deployment, improving the quality of the observations. Third, the UCTD carries a pressure sensor so depth is measured more accurately than by the drop-rate equation typical for an expendable. The design goal for UCTD was to obtain profiles deeper than 100 m at 20 knots (typical of a VOS). This goal has been surpassed, as we are able to profile to over 150 m at 20 knots, and to over 400 m at 10 knots. The first fully operational use of UCTD occurred during a cruise May-June 2004, whose purpose was to examine the effect of internal waves and spice on long-range acoustic propagation. The primary goal of the cruise was to deploy four acoustic moorings on a 1000-km path in the central North Pacific subtropical gyre. UCTD was used while the ship steamed at 10-13 knots between moorings. A total of 97 UCTD casts were completed along the path, resulting in a hydrographic section with a resolution of 10 km horizontally and 5 m vertically. The section clearly showed the effects of thermohaline variability on sound speed.
OS21C-1245 0800h
Measuring Dissipation Rates of Turbulence Kinetic Energy with A Lagrangian Float
This study tests the ability of a neutrally buoyant float to estimate the dissipation rate of turbulence kinetic energy $\varepsilon$ from its vertical acceleration spectrum using an inertial subrange method. A float was equipped with a SonTek Acoustic Doppler Velocimeter (ADV), which measured the vector velocity a meter below the float's center, and a pressure sensor, which measured the float's depth. Measurements were taken in flows with $\varepsilon$ varying from $ 2 \times 10^{-8}$ to $10^{-3}$ W kg$^{-1}$. The Lagrangian acceleration spectrum is white within the inertial subrange with a level proportional to $\varepsilon$. The finite size of the Lagrangian float introduces a highly reproducible spectral attenuation at high frequencies. Estimates of $\varepsilon_{float}$ were obtained by fitting the observed spectra to a model spectrum which included the attenuation effect. The ADV velocity measurements were converted to a wavenumber spectrum using a variant of Taylor's hypothesis. The spectrum exhibited the expected -5/3 slope within an inertial subrange. A value of $\varepsilon_{ADV}$ was computed from the level of this spectrum. These two independent estimates $\varepsilon_{ADV}$ and $\varepsilon_{float}$ were highly correlated, with a correlation coefficient of 0.92, over the 5 decades of $\varepsilon$ measured. This analysis confirms that $\varepsilon$ can be reliably estimated from Lagrangian float acceleration spectra in turbulent flows. For the meter-sized floats used here, the finite size of the float and the noise level of the pressure measurements sets a lower limit of $\varepsilon_{float}> 10^{-8} \rm \,W kg^{-1}$ under most oceanic conditions.
OS21C-1246 0800h
Latent Heat Flux at the Sea Surface Estimated from the TRMM Satellite
Latent heat flux between air-sea interface is one of the dominate factor in atmosphere heat budget, especially over the tropical oceans. Three years (1998-2000) of latent heat fluxes have been calculated using sea surface environmental measurements from the Tropical Rainfall Measuring Mission (TRMM) satellite and the bulk algorithm of Fairall (1996). These results are compared to the global Goddard Satellite-based Surface Turbulent Fluxes version 2 (GSSTF-2) data set and to ship measurements with good agreemenst. GSSTF-2 are derived from Special Sensor Microwave Imager (SSM/I) data collected by a series of satellites from the Defense Meteorological Satellite Program. The input environmental parameters to bulk algorithms include sea surface temperature (Ts), wind speed (WS), and air and sea surface specific humilities (Qa, Qs). These values are estimated for each TRMM pixel. Diurnal variations are available in our dataset due to the processing orbits of the TRMM satellite, which takes 46 days to cover the entire diurnal cycle at each location from 35S to 35N. GSSTF-2 are derived using the gridded daily means of Ts, WS, Qs and Qa. It covers 60S to 60N, but has fewer measurements in the Tropics. Therefore, the seasonal gridded and zonal averages between 35S and 35N are used for comparison between these two data sets. For global oceans over 1998-2000, the correlation coefficients between these two data sets are approximately 0.99 and 0.79 for Qa and WS, respectively. The bias errors are about 0.9g/kg and 0.21m/s. The Qa of TMITF are consistently higher than those of GSSTF-2. The WS are almost the same between 20S and 20N, but TMITF is higher than that of GSSTF-2 for the regions higher than 20 degree of the winter hemisphere. WS is the major cause of the difference between these two data sets. GSSTF-2 uses the daily means of WS from Wentz (1997), and Ts and Ta from the NCEP/NCAR reanalysis. TMITF uses the instantaneous WS and Ts from TMI. Ta is calculated by adding the 6-hourly Ts-Ta difference from ECMWF to Ts. The latent heat fluxes from TMITF are generally a little lower than those from GSSTF-2 except for the regions higher than 20-degree, where TMITF is higher than GSSTF-2. The correlation coefficients and bias errors are 0.72 and -2.98 W/m**2, respectively. Compared TMITF with in-situ ship measurements, the bias (rms) for WS, Ta, Qa, and latent heat fluxes are 0.31 (1.69)m/s, 0.04 (1.35)K, 0.50 (1.49) g/kg and -9.74 (37.08) W/m**2 based on 10 minutes and 20 km collocation. The comparison between GSSTF-2 and in-situ ship measurements have bias(rms) of 0.36 (1.43) m/s, -0.47 (0.94) K, 0.67/(1.40)g/kg, and 0.8 (35.7) W/m**2 based on daily means (Chou 2003).
OS21C-1247 0800h
Salinity Variation in the Pacific Warm Pool Observed with TRITON Buoys
Seasonal salinity variation along 156E in the Pacific warm pool, which is climatologically characterized by high-temperature and low-salinity at the ocean surface, was demonstrated by TRIangle Trans-Ocean buoy Network (TRITON) data. TRITON buoys captured the dominance of low-salinity surface water between 8N and 5N and that of sub-surface high-salinity core, which is more prominent at southern hemisphere than northern hemisphere. On seasonal time-scale, the low-salinity water becomes dominant during boreal fall-winter. Concerning the sub-surface layer, difference of salinity property between northern and southern hemisphere is remarkable, i.e. the southern high-salinity core is deeper and has a higher salinity value compared with northern one. These northern and southern high-salinity core correspond North Pacific Tropical Water (NPTW) and South Pacific Tropical Water (SPTW), respectively. To analyze these water masses, we attempt to represent vertically continuous temperature and salinity profile from discrete profile observed with TRITON buoys. By supposing that T-S relation did not change, we can consider that a sensor observed wider range during tidal motion in the short term. In other words, we can represent T-S relation during tidal motion in the short term by added data. Finally, temperature and salinity profile on density coordinate are reproduced by this T-S relation. By the resultant data set that seasonal appearance of NPTW and SPTW on the equator became clear. Results indicated that a possibility of trace of both water masses by vertically discrete sensor arrangement. In addition, it was proposed that rearrangement of sensor position was necessary to get more effective result.
OS21C-1248 0800h
Comparison of Mixed Layer Depths Calculated Using the Vertically Discrete TRITON Temperature and Salinity Data
To investigate the time series of mixed layer and barrier layer in the western Pacific is crucial for understanding sea surface temperature change associated with the ENSO phenomena, therefore air-sea interaction system in the tropical Pacific. The TRITON (Triangle-Trans Ocean buoy Network) buoy array, which consists the ENSO monitoring system with the TAO array by NOAA/PMEL, has been deployed in the western tropical Pacific for monitoring ocean mixed layer and barrier layer. At this time, the error analysis for mixed layer and isothermal layer depths estimation from vertically discrete temperature and salinity of the TRITON buoy is necessary for further quantitative analysis. This study investigated the comparison of several calculation methods for the mixed layer and isothermal layer depths from the TRITON data, and with the well-managed CTD profiler data from the research vessels. The methods used are based on the Sprintal and Tomzac (1992)_fs method, and the difference to the sea surface temperature was set to be 0.5 degree-C for estimation of isothermal layer depth. In this investigation, the vertical interpolations were tested for two cases, the linear interpolation and the spline (Akima method) interpolation. The new method (_gup-down_h method) by assuming the vertical movement of keeping _gfixed temperature (density) curves below isothermal (mixed) layer_h by internal tidal wave was also tested. The results of comparison indicated, in the statistic comparisons with the CTD profiler data, the estimated isothermal layer (mixed layer) depth from the spline (Akima) interpolation is the best with the errors of 10 meters (9 meters), and the estimated isothermal layer (mixed layer) depth by the new _gup-down_h method is the second with the errors of 12 meters (13 meters). For all estimations of the mixed layer depth and isothermal layer depth, the tendencies to be estimated near the depths of 50 and/or 75 meters were associated with the vertical resolution (25 meters) of the vertical positions of TRITON buoy sensors. The presentation will also include the examples of analysis in the western tropical Pacific by using these mixed layer parameters, focusing on the oceanic responses to atmospheric forcing in each phase of the 2002-2003 ENSO event.
OS21C-1249 0800h
Assessment the Synoptic Variability of Vertical Thermal Structure in Baltic Sea Waters on the Base of in-situ Measurements
The thermal regime of sea's active layer is determined by its interaction with atmosphere, thermal balance, wind and convective water mixing. The question about assessment of synoptic variability of thermal stratification in Baltic Sea waters has not yet solved. The purpose of the present work was to determine the bounds of synoptic variability of vertical temperature profiles T(z) at the all seasons on the example of Bornholm Basin in the Baltic Sea. On the base of the large array of episodic measurements at the international stations BY, situated in key regions of the Baltic Sea, the principles of annual rhythmic of vertical distribution of water temperature are given in the paper [1]. However, this data does not allow separate the synoptic variability from seasonal and inter-annual diapasons, since measurements at fixed horizon belong to different synoptic events at different years. During 1978-1988 the State Oceanographic Institute (Leningrad/Saint-Petersburg Branch) on the base of Russian RV "Rudolf Samoylovich" was carrying out observations of hydrological and hydro-chemical elements of Baltic Sea waters at the stations BY [2]. The originality of carried out work is that for the first time continuous series of measurements for elements of vertical thermo-haline structure with duration from day to several months and discreteness of 3 hour were executed. These observations got name "Multi-daily Stations". This data alongside with the data of episodic observations allows separate synoptic variability of water temperature profile and assess its degree. Vertical thermal structure of sea waters has been typified based on the parameters of profile geometry. The degree of synoptic variability in each element of profile T(z) for all the seasons has determined. It has been showed, that the enthalpy is the optimal thermal regime parameter for separating the synoptic diapason from others. It has also been showed, that synoptic variability of water temperature in deep layer is not significant. References 1. Terziev, F.S., Rozhkov, V.A., Smirnova, A.I.// Hydrometeorology and Hydro-chemistry of USSR seas, Vol. III. The Baltic Sea, Issue 2. Hydro-chemical Conditions and Oceanographic Basis for Biological Productivity, pp. 149-197, 1994 2. Davidan, I.N., Gusev, A.K., Savchuk, O.P., Chernyshova, E.S., Shadrin, P.S.// Representativity of seasonal surveys in the Baltic sea/ Proc. of III BASYS Annual Science Conf., Warnem\"{u}nde, Germany, 20 - 22.09.1999. Paper SP 8 - 7, p. 83
OS21C-1250 0800h
Internal tides and boundary mixing imaged on the Norwegian continental slope
Boundary mixing on continental slopes and other topographic features may help maintain the ocean's stratification by converting low-mode internal wave energy into increased potential energy via turbulence, but existing observations are too sparse to assess whether this process is sufficiently widespread to affect global balances. Here we present a new method for identifying and quantifying internal wave processes in the ocean by acoustic imaging. Seismic reflection images of thermohaline finestructure in the Norwegian Sea that show semidiurnal (M2) internal waves and associated zones of turbulent disruption of finestructure on the continental slope of Norway. The disrupted zone occur at water depths of ~500-650 m, where the slope is critical to M2 internal waves and the water column is highly stratified. Wavenumber spectra calculated from finestructure displacements in the disrupted zones show enhanced energy levels, relative to both open-ocean finestructure and the Garrett-Munk spectrum. These results imply that seismic reflection profiling can remotely detect internal waves, identify the locations and dimensions of sites of boundary mixing, and provide quantitative estimates of internal wave energy in the ocean.
OS21C-1251 0800h
Unexpected tidal variation of the ocean-acoustic velocity
Ocean sound velocity significantly varies at tidal frequency in not only shallow but also deep pert. Unexpected largely semidiurnal fluctuation of ocean-acoustic waves (T-waves), which propagate through the SOFAR channel, is found on the ocean bottom seismometer records for the 1999 submarine volcanic swarm in northern Mariana. The amplitude is one order larger than any previous artificial experiments. Here we report the first in situ evidence that T-wave travel time provide information about vertical movement of seawater due to internal tides. Numerical 3-D modelling shows the internal tide excited by external tidal forcing is particularly large along the Izu-Bonin-Mariana Ridge because of rough topography. A semidiurnal up-and-down movement associated with the internal tide cause an undulation of the SOFAR channel on the order of 100 m, which causes T-wave travel time variations consistent with the observed ones. The results are consistent with the observed travel time variations both in amplitude and phase, demonstrating that T-waves from volcanic swarms can be used to detect oceanic internal tides. Generation of internal tides is an important sink of the external tidal energy so that accurate estimate of conversion of the external to internal tides is essential to close the global tidal energy budget and to understand the Earth-Moon system evolution.
OS21C-1252 0800h
Evolution of Oblique Internal Waves Under the Effect of a Progressive Surface Wave
This paper makes contributions to evolution of internal waves when they are excited by a progressive surface wave. Focus is on a two-layer inviscid fluid system with a triad consisting of a single progressive surface wave and two internal waves. Attention is confined to subharmonic resonance with two internal wavenumber vectors symmetric about the surface wavenumber vector. Multiple scales are adopted and perturbation method is carried to the second order to derive an evolution equation for internal waves. Analytic and numerical solutions are investigated respectively. Two types of analytic solutions are available in certain conditions: hyperbolic tangent solutions and constant solutions. A local analysis is performed next to derive the expression for critical breaking angle of internal waves and it is revealed that this angle is a function of density ratio, lower layer depth and upper layer depth. Finally, study cases are conducted to demonstrate the complete evolution process of internal waves from beginning to breaking.
OS21C-1253 0800h
Seismic Reflection Signatures of Internal Waves and Thermohaline Intrusions in the Norwegian Sea
Water-column reflections acquired on a seismic survey in the Norwegian Sea and corroborated by 35 XBTs at an average spacing of 5 km and 2 XCTDs at both ends of a 172 km line suggest that temperature fine structure from internal wave strains and thermohaline intrusions have distinct seismic signatures. The survey images reflections from temperature fine structure sensitive to changes as small as 0.03 °C at the water mass boundary between the Norwegian Atlantic Current (NwAC) and Norwegian Sea Deep Water (NSDW). Internal wave strains appear in XCTD data from the eastern part of the seismic line near the Norwegian coast showing congruent changes in temperature and density. Reflections in this region have relatively small amplitudes and slope across isotherms corresponding to changes of several degrees Celsius. In contrast, an XCTD taken from the western seaward side of the profile shows several depths where density does not vary with temperature. Salinity is compensating for changes in temperature; thus reflections in this region likely correspond to irreversible fine structure caused by thermohaline intrusions. These reflections have high amplitudes and closely follow isotherms. These results indicate that studying these signatures can provide information about the structure of the internal wave field and isopycnal stirring processes over the lateral and vertical extent of the water column.
OS21C-1254 0800h
Imaging the internal structure of a warm core ring in the Gulf of Mexico using industry high resolution seismic data
We investigate the water column sound speed during an industrial seismic survey from the Gulf of Mexico, imaging a warm core ring that passes through the survey during acquisition. We use single seismic reflection line donated by Schlumberger Ltd., from a 3D survey, to image water column reflections and estimate a sound speed field within the water column during the survey. WesternGeco Ltd. acquired a 65 km line in the Green Canyon area in August of 2001 using a group interval of 12.5m, 412 channels per streamer aboard the MV. Legend. The transect runs southwest from shallow to deeper water across a canyon area and intersects a warm core ring feature traveling eastwards through the survey area. We present a migration of the water column data to image the water masses within a warm core ring with a resolution of 6.25 m along the sail line and a 15 m vertical resolution. Images processed show strong seismic reflectors due to temperature variations within the water column. The stack section of the line shows a distinct dipping event in the reflectors as the line is acquired moving towards the center of the ring. A distinct fine structure is present in the reflectors at a depth of approx 750m at the edge of the ring rising to approx. 600m depth towards the center of the ring. The affect of the warm core ring seems to significantly perturb the sound speed profiles within the water column along the entire 64km line with the effects of the ring being concentrated in the 225m to 1000m depth range. Velocity analysis indicates a complex velocity profile highly spatial variant through the ring structure. This survey provides a detailed image of water sound speed changes due a highly localized feature within the water column from data acquired during an industry seismic survey.
OS21C-1255 0800h
Long-term estimates of geostrophic transport in the Gulf Stream
Western boundary currents such as the Gulf Stream transport tremendous amounts of mass and heat from the warm tropics to the cooler temperate zones. As such, accurately quantifying long-term Gulf Stream transport is critical to understanding meridional heat transfer and associated global climate. In this study, current measurements in conjunction with satellite altimetry data are incorporated in a predictive model of Gulf Stream mass transport. Nearly 2 weeks of in-situ measurements were collected in the section of the Gulf Stream that flows along the outer continental margin adjacent to South Carolina at approximately 31>|30 N latitude and 79>|00 W longitude. To characterize the hydrodynamic regime, full water column currents were measured using 2 hull-mounted Acoustic Doppler Current Profilers (ADCPs) over a 2-week period in August 2003. CTD profiles were obtained a minimum of twice per day and will be used to estimate the geostrophic velocity using the thermal wind equation. Depth-independent estimates of the geostrophic current will be computed from cross-stream sea surface height anomaly (SSHA) data obtained from the Jason-1 satellite altimeter. Historical SSHA data will be used to produce a decadal time series of Gulf Stream mass transport in the South Atlantic Bight.
OS21C-1256 0800h
Zonal Currents Over the Mid-Atlantic Ridge North of 50N Observed With RAFOS Floats
In the late 1990s, over 100 acoustically-tracked RAFOS floats were deployed at the thermocline level between 45 and 55N in the North Atlantic to investigate the warm water pathways from the subtropical to subpolar regions. This was part of the U.S. WOCE Atlantic Circulation and Climate Experiment (ACCE). The trajectories of floats released upstream (west) of the Mid-Atlantic Ridge (MAR) are analyzed here to determine how and where the various branches of the North Atlantic Current cross the MAR. They show relatively strong eddy activity upstream and downstream of the ridge axis, and the presence of several long-lived, quasi-stationary meanders and eddies immediately upstream of the ridge. In spite of this, the float trajectories generally collapse into narrow bands over the ridge axis as they are funneled over several deep gaps in the MAR, especially the Charlie-Gibbs Fracture Zone and the Faraday Fracture Zone. The high-resolution trajectories also illustrate the influence of smaller-scale features of the MAR (including seamounts and the rift valley) on the current pathways, even though the floats are up to 1500 m above the ridge crest. Fewer floats drifted westward in the northern subpolar gyre, but they too appear to be directed over gaps in the Reykjanes Ridge as they crossed from the Iceland to Irminger Basins.
http://www.whoi.edu/science/PO/people/abower/ACCEmain.html
OS21C-1257 0800h
Spatial and Temporal Variability of Labrador Sea Water Export Pathways
Labrador Sea Water (LSW), a critical element of the bottom limb of the Atlantic meridional overturning cell, has been shown to be a particularly sensitive indicator of changes in sea surface conditions on decadal time scales. Though the export of these signals out of the subpolar region is crucial for our understanding of how climate signals spread, the variability of Labrador Sea Water pathways on decadal time scales is not clearly understood. Recent profiling float studies in the subpolar region have shown surprisingly little evidence of an export pathway via the Deep Western Boundary Current (DWBC). Floats launched in the Labrador Sea, including some intentionally placed in the DWBC, did not follow the western boundary to subtropical latitudes, but instead were pulled offshore to drift eastward at the subpolar-subtropical gyre boundary, raising questions addressed by this study, namely: Is there a dominant pathway for waters from the subpolar region to reach the subtropics? Is there temporal variability in the strength or dominance of these pathways? Are these pathways sensitive to climate variability? In this study, we combine data from the Bedford Institute of Oceanography Climate database and from Hydrobase 2, a database of hydrographic profiles, to address these questions. The study area covers most of the North Atlantic, from $30\deg$N to $65\deg$N and from $80\deg$W to $5\deg$W. We have focused on three density surfaces most common to LSW, $\sigma$$_{1.5}$ = 34.62, 34.66, and 34.68 kg m$^{-3}$. We use well-known properties of LSW, including its low temperature, low salinity, low potential vorticity, and high oxygen content, to trace the changing pathways of LSW over time. Understanding these changing pathways is crucial to understanding how the oceans will respond to climate change.
OS21C-1258 0800h
Bathymetric Recirculations in the Labrador Sea
Float data from the Labrador and Irminger Seas have revealed a number of permanent recirculation cells offshore of the shelf-break boundary current. Previous studies have concluded that these cells form as a result of cyclonic wind forcing east of Greenland, however we argue here that they instead arise from interactions between the boundary current and the continental shelf and slope. Two issues are noteworthy; winds in the area are variable, and are therefore not obvious candidates to drive the relatively small-scale steady recirculations. Second, float data with overlaid bathymetry contours clearly show that recirculations are established where the boundary current crosses isobaths into deeper water. Numerical experiments with idealized and realistic bathymetry confirm that such interactions can result in recirculations, and that wind forcing is of lesser importance.
OS21C-1259 0800h
Surface Vector Velocity Estimates and Gulf Stream Observations From the UMass Dual Beam Interferometer
The Dual Beam Interferometer (DBI) developed by University of Massachusetts (UMass) consists of two C-band along-track interferometric synthetic aperture radars (ATI-SAR). The beams of this airborne system are squinted 20 degrees forward and aft of broadside allowing surface vector velocity estimation in a single aircraft pass. The instrument has been deployed several times over the period of last two years off coastal areas of Florida on a National Oceanic and Atmospheric Administration's (NOAA) WP-3D plane in collaboration with the Naval Research Laboratory (NRL). During 2002-2003 the instrument has undergone a series of tests and engineering flights with the August 2003 data producing the first interferogram. March 2004 flights were mainly focused on the western boundary of the Gulf Stream off Cape Canaveral, Florida. Simultaneous imagery of the sea-surface temperature field were obtained using NRL's Infrared (IR) camera, which was mounted in belly of the aircraft. Multiple passes over the Gulf Stream were made under a range of environmental conditions and viewing geometries relative to the Gulf Stream current and the wind. Additional flights were made over the barrier islands west of Ft. Meyers, Florida at times of near maximum ebb tidal flow. This paper will present initial estimates of the surface vector velocities for each area. The Gulf Stream velocity estimates show a current maximum of 1.5 m/s across the edge of the Stream which is consistent with estimates of the current from IR imagery using feature tracking. Estimates of the flow between the barrier islands are of the order of 1.5 to 2 m/s, which agrees well with the predicted tidal flow.
OS21C-1260 0800h
The Nuka Arctica Line
In order to develop an accurate understanding of the mean circulation and its variability in the northeast Atlantic over a wide range of timescales, the Nuka Arctica project was established to measure currents directly using a hull-mounted ADCP onboard the container vessel `Nuka Arctica' that operates between Denmark and Greenland on a three-week schedule. Since late 1999, the `Nuka Arctica' has collected velocity data from nearly 50 transects. The circulation around the Reykjanes Ridge stands out very clearly with a southward flow on its eastern flank and a well-defined northward flow along its western slope. We also find a well-defined flow northward through the Iceland Basin. The East Greenland Current as it passes around Cape Farewell stands out clearly. These mean flow patterns appear to be robust thanks to the many sections available. In contrast, except for the East Greenland Current, these currents cannot be discerned in any single section. There are two reasons for this: First, as is well-known, the eddy velocity field is much larger than the mean flow, and second, the mean flows along the ridge are rather narrow and topographically defined. Thus they cannot be recovered from individual sections by simply averaging over a longer section. The fact that the mean field emerges so clearly through ensemble-averaging underscores how effective repeat sampling from volunteer observing vessels can be. The long-range objective of this program is to obtain a very accurate estimate of the mean flow relative to which low frequencies variations and their causes can be explored.
http://www.gfi.uib.no/forskning/Nuka_Arctica
OS21C-1261 0800h
Deepwater formation in the Southern Weddell Sea, processes, pathways and fluxes
Ice Shelf Water (ISW) is the final product of the melting process underneath the floating ice shelves in the Antarctica. Recent drastic break-ups of the Larsen ice-shelf in the Weddell Sea has vitalised the question if this melting has increased. The most efficient production of ISW takes place under the immense Ronne - Filchner Ice shelves in the Southern Weddell Sea. The corresponding ISW flow out of the region was located in 1977, and a key location for long term monitoring was identified. Since then we have succeeded in occupying this station with instrumented moorings for about 5 years, which have given us valuable information of variability of the sub-ice shelf and continental shelf circulation. However, in addition to serve as an indicator for Antarctic ice-cap melting, it turns out that the ISW flow contribute to the formation of the Antarctic bottom water. Therefore it is driving the thermohaline circulation, which has a great impact on the global climate. There are several processes and regions in the Antarctic of importance for the bottom water formation. However, recent international efforts indicate that the ISW overflow and its cascading towards large oceans depths as a bottom trapped jet entrain waters from above, increasing the volume transport by a factor of about 2.5. The resulting volume transport estimates indicate that the processes involving ISW is dominating the deep and bottom water formation in the Antarctic.
http://www.bjerknes.uib.no/research/
OS21C-1262 0800h
Zonal Variation of Meridional Overturning, Heat and Salt Fluxes in the Antarctic Zone
We present results from the Antarctic region of a global box inverse model, designed to resolve circulation in coarse sectors of the Antarctic Zone, distinguishing the Weddell Sea, Ross Gyre, and South Indian-Enderby Basin sectors near the continent. We address in this study the connections between the upper and deep cells of meridional circulation around Antarctica using the {\sc woce s4} section, a Weddell Sea {\sc woce} line together with a new compilation of direct current meter measurements, and other hydrographic sections extending onto the slope. The role of the system of nearly barotropic gyres around the Antarctica is explored. Climatologies do not represent the high buoyancy loss responsible for the bottom water formation in the high latitudes where data are scarce. This work aims also to give a better representation of the air-sea fluxes in the Southern Ocean, compatible with a global inverse model including the parameterization of entrainement, polynya effects and CFC derived constraints. The role of the Ekman transport and eddy fluxes in the meridional exchanges are considered.
OS21C-1263 0800h
Seismic Imaging of the Antarctic Circumpolar Current near Drake Passage
Inspired by the recent work of Steven Holbrook and colleagues, we have reprocessed a set of legacy seismic reflection profiles in order to image features associated with thermohaline circulation. As a starting point, we selected academic and industrial datasets from a region which encompasses the Falkland Plateau just east of the Drake Passage which is an important choke point for deep-water circulation. These datasets cross the Sub-Antarctic and Polar Fronts associated with the Antarctic Circumpolar Current and associated water masses. As expected, careful velocity picking during processing considerably improved the acoustic images. Unfortunately the upper 400 milliseconds is contaminated by the bubble pulse of the airgun source. This bubble pulse also contributes to the general `ringiness' of the images. In the Argentine Abyssal Plain, the intrusion of North Atlantic Deep Water into Lower Circumpolar Deep Water is spectacularly observed. Toward the base of this intrusion, a mesoscale eddy is visible. In the Falkland Trough, just south of the Falkland Islands, seasonal variations of the thermohaline circulation can be deduced from a set of profiles which were shot at different times. In the Scotia Sea, the Polar Front is clearly visible, separating acoustically stratified waters to the south from acoustically blank waters to the north. We have used WOCE and other legacy hydrographic datasets to corroborate our results.
OS21C-1264 0800h
Seismic imaging of thermohaline circulation: observations from the Antarctic Circumpolar Current
The evolution of the Antarctic Circumpolar Current and its components is undoubtedly of considerable importance in moderating climate change. Despite this global significance, temporal and spatial interactions between circumpolar water masses and the general thermohaline circulation of the oceans are poorly understood. Here, we present observations from a controlled-source seismic reflection experiment which we believe demonstrate the potential of four-dimensional (i.e. time-lapse) monitoring of acoustically distinctive water masses. The approximately north-south seismic reflection profile is 1200 km long and crosses both the Sub-Antarctic and Polar Fronts where they loop around the Falkland Plateau, east of Drake Passage. These data were acquired with a 5,600 cubic inch airgun array and a 6 km streamer in October 1998. Vertical and horizontal resolution is 5--10 meters. In the Argentine Abyssal Plain, the interaction between North Atlantic Deep Water and different components of the Antarctic Circumpolar Current is spectacularly imaged: thermohaline fronts, salt fingering and mesoscale eddies are observed in detail. Our seismic observations can be independently corroborated by legacy hydrographic measurements. The lack of detailed correlation implies temporal variation. Across the Falkland Plateau, the Sub-Antarctic Front is imaged in several places as expected. In the Scotia Sea, stratification of the water column is imaged south of the Polar Front, which is clearly imaged dipping northwards. These preliminary results suggest that a co-ordinated series of seismic reflection experiments in the southern oceans could yield important information about diapycnal mixing.
OS21C-1265 0800h
The Transit Time Distribution of the Subtropical-Tropical Water Exchange in the Pacific Ocean
The transit-time distribution (TTD) of the subtropical-tropical thermocline water exchange in the Pacific Ocean is simulated in an ocean general circulation model. The exchange time scales that are mainly due to advection are about 10 years, consistent with previous time scale estimates by neglecting the effect of mixing. However, only about 10% of the water in the equatorial thermocline has age less than the advective time scale, and the rest has age much longer due to mixing. In addition, the mean time scale, which considers the effects of both advection and mixing, for the subtropical surface waters to reach the equator is much longer (over 100 years) than the advective time scale. The long mean time scale and broad TTDs in the equtorial Pacific suggest that mixing is important for the thermocline water exchange.
OS21C-1266 0800h
Eddies in the western tropical Pacific observed using a synthetic moored array of autonomous gliders
A synthetic moored array composed of autonomous gliders was used to characterize mid-ocean mesoscale variability in a 100 km x 100 km domain east of Luzon Strait in May 2004. Each of five gliders in the array maintained geographic position while profiling between the surface and 200 m. The resulting time series at each array position, including slab velocity estimates every 2 hours and 200 m high-resolution CTD/optical profiles every 40 minutes, may be interpreted in the same manner as a physically-moored chain of instruments. This approach provides an efficient means for a single survey ship to rapidly obtain spatially distributed time-series data at low cost and with minimal need for on-site technical support. The typical equivalent watch circle of a glider performing a synthetic mooring mission was less than 3 km, comparable to that expected from a bottom-moored surface mooring in similar (6000 m) water depth. Temperature, salinity, and velocity time series exhibit strong semidiurnal and diurnal fluctuations. Similar temporal variability is also evident in a deep maximum in chlorophyll fluorescence observed near 120-130 m. We will present an overview of this experiment including comparisons with simultaneous shipboard measurements, remote observations of sea surface height and temperature, and numerical model results.
http://glider.whoi.edu
OS21C-1267 0800h
Dynamics of separation of Kuroshio in eddy-permitting general circulation models in an idealized basin
Separation of the Kuroshio is studied by using a 1/6$^\circ$ $\times$ 1/6$^\circ$, flat-bottom ocean general circulation model (OGCM) with an idealized coastline, which simplifies the southern coast of Japan without the Izu Ridge. The western boundary current, the modeled Kuroshio, separates at the edge of the coastline far south of $\mbox{curl}\tau = 0$ line. The front after the separation, the modeled Kuroshio Extension, extends 15$^\circ$ in the east and has fairly steady meandering pattern accompanied with northern and southern recirculations. Despite the rather simplified settings, the modeled Kuroshio Extension is very similar to that obtained in a 1/10$^\circ$ $\times$ 1/10$^\circ$ OGCM with the realistic topography and forcings. Vorticity analysis reveals that the balance along the modeled Kuroshio Extension is between advection of relative vorticity and stretching of planetary vorticity term (f$\frac{\partial w}{\partial z}$) above the thermocline, while it is between $\beta$ and stretching terms at mid-depths. When depth-integrated, the vorticity balance is between $\beta$ and advection of relative vorticity terms, indicating that the meandering pattern is stationary Rossby wave. The position of the separation is constrained near the edge of the coastline and found to be associated with an adverse value of ageostrophic pressure gradient. This implies that the coastline with a edge encourages the Kuroshio separation, analogous to separation of boundary layer from a rigid wall with a salient edge in nonrotational flame. The spinup phase of the modeled Kuroshio is investigated in order to examine how the separation and extension mentioned above are formed. The initial state is created by interpolating the steady state of a corresponding coarse resolution model. At the very first stage damped Rossby waves are found near the western boundary current just south of $\mbox{curl}\tau =0$ line. Then a premature separation appears at the edge of the coastline after the western boundary current becomes highly inertial. In this phase the modeled Kuroshio does not steadily extend eastward, but usually return to the western boundary immediately after the separation. The modeled Kuroshio Extension is formed after strong recirculations and fairly uniform potential vorticity are found at the middepth. They are presumably created by intermittent eastward intrusion of the modeled Kuroshio. This may imply that the steady path of the Kuroshio Extension can not be obtained when the mid-depth layers stand still, since stretching term is dominant in the upper layer vorticity balance and this needs movable mid-depth layers.
OS21C-1268 0800h
Decadal variability of the upper ocean in the western part of the midlatitude North Pacific simulated by Meteorological Research Institute Community Ocean Model (MRI.COM)
Decadal variability of the North Pacific upper ocean is simulated by Meteorological Research Institute Community Ocean Model (MRI.COM). We analyzed the results focusing on the changes in the heat content and the sea surface height (SSH) in the western part of the midlatitude North Pacific, and the North Pacific Subtropical Mode Water (NPSTMW). Simulated heat content and SSH in the western part of the midlatitude North Pacific has bidecadal variability in conjunction with the observed sea level changes on the Japan coast, and their variability has two distinct modes. The first SSH anomaly mode exhibits a large-scale feature centered at 40N, and is strongly related to the meridional shift of the westerlies over the central North Pacific. The second SSH anomaly mode, which indicates a north-south dipole structure, is determined by the change in the magnitude of the westerlies. The meridional shift and change in the magnitude of westerlies yield the anomalous wind stress curl at the 40N and 30N, respectively. Then, these wind stress curl anomalies dynamically force the thermocline below, and finally affect each mode of the sea level variability in the western North Pacific through the baroclinic Rossby waves for 3 years (at 30N) to 5 years (at 40N). NPSTMW characterize the upper thermal structure in the western part of the midlatitude North Pacific. Decadal variability in the NPSTMW is caused by change in the horizontal heat advection into the NPSTMW formation area due to the meridional shift of the westerlies. Though surface heat flux compensates for the horizontal heat advection in 1970s and 1980s, both heat budget terms change in the same phase in the 1990s and 2000s, resulting in the large variations of the NPSTMW characteristics.
OS21C-1269 0800h
On the Nonlinearity of the Kuroshio Current South of Japan
The Kuroshio south of Japan exhibits three stable paths: One with a meander centered at 138E, one without the meander following a straight path and a third with a large meander centered at 135E upstream of the Izu ridge. We have computed the bifurcation diagram of a limited area 2 layer quasi-geostrophic model of the Kuroshio south of Japan. The bifurcation diagram represents two of the three stable paths and one unstable path. The nature of the unstable path and the transition from a stable path to an unstable one is investigated by analyzing the leading eigenvectors and eigenvalues.
OS21C-1270 0800h
The Effects of Tsushima Warm Current and Surface Boundary Forcing on the Thermohaline Circulation of the East/Japan Sea
Watanabe et al. (2003) show that the temperature of the deep water in the northern part of East/Japan Sea (EJS) oscillates with 20 year cycle as the North Pacific Index, although the intermediate to deep circulation of EJS is independent of that in the North Pacific. This suggests that the interdecadal scale variation in the EJS is caused by external factors such as the atmospheric conditions and the Tsushima warm current (TWC). Using a four-box model based on Stommel (1961) with an inflow and outflow system, we have investigated the roles of the external forcing in the interdecadal scale variation of the EJS thermohaline circulation. The model shows that the effect of TWC is manifested more strongly in the northern boxes where watermass formation occurs than the southern boxes, although the southern surface box is connected to TWC directly. The effect of the surface boundary conditions can be observed in all surface boxes, however. The model also shows TWC could have strong effect on the deep water mass formation rate.
OS21C-1271 0800h
Heat Balance in the Southeastern Indian Ocean From Float Data
The complete set of the {\sc woce alace/palace} array in the Indian ocean and more than two years of data from the {\sc argo} experiment are examined to study the heat content variation in the Southeastern Indian Ocean. The circulation in this area is estimated via objective analysis. Various mixed layer depth definitions illustrate the importance of the seasonal cycle. Several methods to evaluate heat content calculations from the float profiles are employed, together with sensitivity tests, and compared with a newly developed satellite air-sea flux and {\sc ncep} climatological products. The question of a dominant balance in the oceanic budget between ocean heat storage and air-sea fluxes is studied with Ekman heat transport and advection estimates. The study also focusses on the formation and modification processes of Subantarctic Mode Water in this region of the Southern Ocean. The relation of the observed variability to the Antarctic Oscillation Index (AAO or SAM) is assessed.
http://argo.ocean.fsu.edu
OS21C-1272 0800h
Heat Budget estimation of the Eastern Arabian Sea using Simple Ocean Data Assimilation Techniques
Estimation of the monthly climatological heat budget of the Eastern Arabian Sea (6°N to 24°N and 68°E to 78°E ) is carried out for the top 50 m using oceanographic data from Simple Ocean Data Assimilation (SODA) model output and atmospheric surface heating fluxes over the air sea interface using Southampton Oceanographic Centre Climatology (SOC) for the periods 1990 ? 2001. We address the various roles played by the net surface heat flux and the local and remote ocean dynamics of the near surface heat budget in the eastern Arabian sea. A rough balance between the rate of change of heat and the fluxes of heat across the regional boundaries owing to advective and non advective processes is observed. During the summer monsoon oceanic processes play a major role in removing heat from the eastern Arabian Sea region of which horizontal advection is a major contributor. During the (NE) winter monsoon excess heat is downwelled by vertical velocity components (SODA) thus cooling the control volume. The accuracy of the vertical components of velocities is tested in balancing the heat budget. At 100 m depth a better closure is attained when vertical velocities components derived from mass balance were used in the heat equation. From the analysis of these datasets, this paper shows the ability of these datasets for estimating the heat budget of the eastern Arabian Sea.
OS21C-1273 0800h
Seasonal Characteristics of Circulation in the Southeastern Tropical Indian Ocean
The circulation in the southeastern tropical Indian Ocean is studied using historical temperature and salinity data. A southward shift of the subtropical gyre at increasing depth dominates the structure of the annual mean circulation. Near the southern Indonesian coast, the westward South Equatorial Current (SEC) is at the sea surface and strongest near 10°-11°S, reflecting strong influence of the Indonesian Throughflow (ITF). In latitudes 13°-25°S the SEC is a subsurface flow and its velocity core deepens toward the south, falling below 500 m at 25°S. The Eastern Gyral Current (EGC) is a surface flow overlying the SEC, associated with the meridional gradients of near-surface temperature and salinity. The ITF supplies water to the SEC mainly in the upper 400 m, and below that depth the flow is reversed along the coast of Sumatra and Java. Monsoon-winds strongly force the annual variation in circulation. Dynamic height at the sea surface has a maximum amplitude at 10°-13°S, and the maximum at deeper levels is located further south. Annual variation is also strong in the coastal wave guides, but is mainly confined to the near-surface layer. Although the South Java Current at the sea surface is not well resolved in the present dataset, semiannual variation is markedly evident at depth and tends to extend much deeper than annual variation along the coast of Sumatra and Java.
OS21C-1274 0800h
Characterizing Submesoscale Ocean Color Variability in the Sargasso Sea in the Vicinity of the Bermuda Atlantic Time-series Site (BATS): A Geostatistical Approach
Using the geostatistical method of semivariogram analysis, high resolution SeaWiFS imagery (1.1 km) is analyzed to determine ocean color variability on the submesoscale (1 - 10 km). Numerous studies have demonstrated the importance of mesoscale (10 km - 200 km) nutrient upwelling in structuring and fueling ocean productivity in oligotrophic environments; modeling experiments suggest further enhancements of productivity due to submesoscale physics. Our study area, the Sargasso Sea surrounding Bermuda, is selected based on an earlier study of global mesoscale ocean color semivariance that shows moderate levels of mesoscale variability and a high level of unresolved variability. A time-series of data is analyzed, and one- and two-dimensional semivariograms are produced for each month. Based on these semi-variograms, we demonstrate that much of the previously unresolved variability is indeed caused by submesoscale structures and that submesoscale and mesoscale variability are comparable in magnitude. Anisotropy on local scales, $\sim$10-20 km, is observed based upon semivariograms computed from 20 km$^{2}$ subsamples of single day images, showing that much of the submesoscale signature is occurring in elongated filaments. Unresolved submesoscale variability may be non-geophysical noise (instrument, aerosols, algorithms {\em etc.}) as well as variability on an even finer scale.
OS21C-1275 0800h
Wind Stress Distributions on a Tree-Canopy Sheltered Lake
Wind stress over a lake is generally the most significant driver of whole-lake circulation and lake surface layer mixing. The spatial and temporal distribution of atmospheric flow velocity (and hence wind stress) over the lake is controlled by the roughness transition that the flow encounters as it crosses the shoreline onto the water surface. Well-established shear stress relationships for flat plates and open water surfaces indicate that experiments on flat plates may reasonably represent stress distributions over open water surfaces for wind speeds less than 10 m/s. Field measurements of wind speed profiles conducted on a frozen lake surface and at an agricultural transition of tall corn (1.7 m) to short rye stubble (less than 10 cm) suggest the presence of a blending layer that moderates the momentum flux that is transferred between the upper and lower internal boundary layers present immediately after a roughness transition. The data is compared to the blending layer models and the validity of various blending layer formulations is evaluated. The streamwise evolution of the surface internal boundary layer is quantified for the two cases at hand. This downwind evolution can be regarded as the result of interplay between a surface "equilibrium layer" and the growing "wedge" of the blending layer.
OS21C-1276 0800h
The Bidirectional Reflectance Distribution Function (BRDF) of the Ocean: Effects of Wave Representation
The specular reflection of the Sun off the ocean, or sun glint, is of major concern for ocean remote sensing. Typically, data from in and around the sunglint region are discarded because of the unknown contribution to the measured radiances or because of sensor saturation. On the other hand, accurate knowledge of the sunglint properties enables retrievals of atmospheric parameters. The challenge of the ocean retrieval problem is to get the ``water leaving radiance'', $L_{w}$, by subtracting the Rayleigh scattering, aerosol scattering, water vapor, ozone, and sun glint from the measured radiances at the top of the atmosphere (TOA). Thus, the task is to correct for both the atmospheric contribution and for surface effects. Two simplifying assumptions that are frequently employed in ocean remote sensing are that the ocean BRDF is isotropic and that one can de-couple the radiative properties of the atmosphere from those of the surface. Our previous studies have shown that neglecting the inherit coupling between the atmosphere and surface can lead to large errors in the retrievals. In order to do retrievals over bright, as well as darker surfaces, it is necessary to account for this coupling between the surface and the atmosphere. In the present study we use models for the reflection of light off the ocean surface to calculate the ocean BRDF. The differences between the various models are investigated as is the effect of using different types of wave statistics (e.g. Cox Munk). We present results from calculations where we vary the wind speed and direction as well as other parameters affecting the ocean surface. The error introduced in ocean retrievals by assuming an isotropic BRDF is assessed, and methods for improved treatment of sunglint are suggested.
http://odin.mat.stevens-tech.edu/
OS21C-1277 0800h
Validation of AVHRR Pathfinder Version 5.0 Sea Surface Temperatures
An improved, 20-year long sea surface temperature (SST) data set based on NOAA Advanced Very High Resolution Radiometer (AVHRR) observations and an improved Pathfinder algorithm has been developed by the NOAA National Oceanographic Data Center and the University of Miami Rosenstiel School of Marine and Atmospheric Science. This data set implements numerous improvements over previously available version 4.x Pathfinder data sets, including a finer spatial resolution, use of ice masks in quality level determinations, and greater inclusion of coastal and inland waters. Validation studies conducted on this AVHRR Pathfinder Version 5.0 collection have been undertaken. Both quantitative and qualitative assessments of these SST observations will be presented, with an emphasis on the improved coastal coverage, reduced biases compared to operational AVHRR SSTs, enhanced climatologies, and refined high-latitude observations.
http://www.nodc.noaa.gov/sog/pathfinder4km/FallAGU2004
OS21C-1278 0800h
Aerosol Correction for NPOESS VIIRS Sea Surface Temperature
Satellite sea surface temperature (SST) retrieval has been available for nearly three decades. The effects of high aerosol concentrations on SST retrievals are not well characterized and are a significant concern in the Visible/IR Imager/Radiometer Suite (VIIRS) retrieval algorithm. VIIRS will fly as a primary sensor on the National Polar-orbiting Operational Environmental Satellite System (NPOESS) program. The first opportunity for VIIRS will be as a payload on the NPOESS Preparatory Project (NPP), currently scheduled for launch in 2006, which provides a great opportunity to investigate this problem. This study utilizes VIIRS proxy imagery and VIIRS aerosol products to study this source of error. Preliminary results will be presented at the meeting. The VIIRS aerosol products are comparable to the MODIS aerosol products, while VIIRS improves the spatial resolution. A comparison between the aerosol-corrected SST's and non-corrected SST's indicates that the VIIRS aerosol products are useful for applying aerosol correction in the SST retrieval.