OS34N-01
The Wind- and Ice-Driven Response of the Mackenzie Shelf and Amundsen Gulf.
An extensive moored array was deployed along the shelf-break of the Mackenzie Shelf and within Amundsen Gulf from September 2003 to September 2004 as part of the Canadian Arctic Shelf Exchange Study (CASES). We use data from this moored array to describe the ocean's response to surface-stress, focusing on the effect of individual events and the relative contributions from wind and ice-generated stress. Of particular importance are shelf-break exchange processes which are critical to the development of the Arctic halocline and to the flux of deep water onto the shelves. Upwelling of nutrient-rich water to the shelf can aid primary production and appears to be enhanced by topographic irregularities such as cross-shelf canyons. Near Cape Bathurst, the Mackenzie Shelf abruptly narrows and ends at Amundsen Gulf; thus along-shelf flow generated by upwelling-directed surface stress will force enhanced upwelling near the Cape.
OS34N-02
Insights From Tracer Hydrography in Passages of the Canadian Archipelago, Baffin Bay and Hudson Strait
Tracer hydrographic sections were carried out in the summer of 1997 from the CCGS Louis. S. St. Laurent in Smith, Jones and Lancaster Sounds, Baffin Bay and Davis and Hudson Straits. In addition to CTD profiling, analyses included nutrients, dissolved oxygen, alkalinity, oxygen isotopic composition of water, barium (Ba), aluminium (Al), and chloro-fluorocarbons and several natural and artificial radioisotopes. Tracer distributions in this region are a complex function of mixing of Arctic and North Atlantic source waters, sea ice, icebergs, precipitation and river inputs and active biogeochemical processing. Our temperature, salinity and nutrient distributions for the three northern archipelago passages are remarkably similar to levels reported for the summer of 1977 except for Si levels in eastern Smith Sound. The possibility that this difference signals the tapping of different source water types within the Arctic Ocean in these different time periods will be discussed. As a preliminary examination of variability in the observations, factor analysis was carried out on the composite data set excluding the much more sparse radiotracer data. Not surprisingly, the initial analysis showed the variability of the tracers depended most strongly on whether they occur in gaseous or solute form. Hence the solutes were analyzed separately and the factors that explain the majority of their variability appear to be related to mixing among the sources described above. The distribution of these sources as interpreted from our observations is largely in accord with previous discussions of circulation in the region. Although it is not dominant in most places, there is a factor expressed primarily through Al, and to a lesser extent Ba and Si that represents non-conservative input. This component is evident in deep Jones Sound and Baffin Bay whose waters are relatively slowly renewed and to a lesser extent at a few passage stations. Additional tracer sections were undertaken at the locations north of Davis Strait from the USCGC Healy in the summer 2003. Aspects of this data are currently being finalized as of this writing and will be used to provide another basis for comparison. Tidally corrected shipboard ADCP measurements during this mission permit the first estimates of instantaneous fluxes of the chemical parameters through the northern sections.
OS34N-03
Water Transport and Freshwater Fluxes through Davis Strait: Initial Results from a new Measurement Program
Davis Strait is a critical site for investigating freshwater exchange between the Arctic and North Atlantic Oceans and an ideal location for monitoring temporal and spatial variability of the critical upstream boundary condition for Labrador Sea convection. Fluxes through the Strait represent the net integrated Canadian Archipelago throughflow, modified by terrestrial inputs and oceanic processes during its southward transit through Baffin Bay. By the time they reach Davis Strait, Arctic waters already embody most of the transformations they undergo prior to exerting their influence on the deepwater formation sites in the Labrador Sea. Hydrographic sections occupied during ship-based surveys and by an autonomous underwater glider supplement year-round current, temperature and salinity measurements collected by an extensive moored array that characterize watermass variability, currents and transport(already have year-round). Sections occupied in autumn 2004 and 2005 reveal a southward-flowing, surface-intensified layer of Arctic water (S ~ 31) that stretches from the Baffin coast to the Greenland shelfbreak. The West Greenland current carries fresh Arctic waters northward in a 50 m thick layer over the Greenland shelf. Deeper (200-600 m), a core of high salinity Irminger water moves northward along the Greenland shelfbreak. High-resolution sections occupied by an autonomous Seaglider capture deformation scale variability, resolving small-scale recirculation to provide volume and freshwater transport estimates between the Strait's 400 m isobaths. Between the Baffin and Greenland shelves, velocity records from 6 subsurface moorings with separations ranging from 16 to 62 km show only weak lateral correlation. Southward flow persisted year-round at all sites except the two situated over the Greenland slope, which captured the northward West Greenland current punctuated by periods of southward flow. Bottom-mounted instruments and a prototype shallow float collected the first year-round measurements over the narrow Baffin and broad West Greenland shelves. Instruments mounted on four bottom landers and a 20 m float recorded variability at short lateral scales over the Baffin shelf, revealing a narrow, fresh jet flowing within a kilometer of the coast. During the ice-free period, a surface-intensified Arctic water layer moved southward over the Baffin shelf. The salinity profile reverses during ice-covered months (freshest waters near the bottom), perhaps due to brine rejection. Four landers deployed over the West Greenland shelf suggest that variability at larger lateral scales dominates this broad region.
http://iop.apl.washington.edu
OS34N-04
Polynya Dynamics and Export of Dense Water: Results From the Storfjord Laboratory
Storfjorden is a 190 km long, 190 m deep bay in southeastern Svalbard around 77 N. A recurrent polynya produces sea ice and brine-enriched shelf water which is exported from the site towards the deep ocean. This site alone accounts for order 10 % of the total dense water export from shelf polynyas around the Arctic Ocean and regularly produces water with salinity higher than that of the Atlantic Water that passes by west of Spitzbergen. We have exploited the relative proximity of the site to infrastructure on Svalbard to collect simultaneous atmosphere, ice and ocean data during both summer and winter over the past 7 years, using research vessels and small boats, helicopters and bottom moored instrumentation. Observations reveal clear connections between northeasterly winds, polynya opening events, salinity buildup, subsequent outflow across the sill and mixing along the path to the main shelf break. The present contribution will give a brief review of findings from this relatively well sampled laboratory for polynya dynamics, dense water flow and export, and discuss status and research challenges for understanding and predictive modelling of such systems and their response to environmental change.
OS34N-05
Towards a Warmer Arctic Ocean: Results of Three Years of Observations of the Atlantic Water Properties along the Siberian Continental Slope
There is abundant evidence that the Arctic Ocean is in transition towards a new warmer stage. Among them, the warming of the Atlantic water (AW) layer that carries significant amount of heat into the Arctic Ocean along the basin margins has been recently mentioned. The focus of our study is to track the propagation of several AW warm impulses that have penetrated into the Arctic Ocean through the Fram Strate in 1999-2000. Here, we present our preliminary analysis of observational oceanographic data obtained from the Nansen and Amundsen Basins of the Arctic Ocean in 2002-05. The properties of the AW layer were evaluated using a three year-long record of water temperature and salinity from moorings deployed in September 2002 at the Laptev Sea continental slope. Data from 2002-05 CTD surveys of the NABOS (i/b "Kapitan Dranitsyn") and ARKTIKA (r/v "Akademik Fedorov") expeditions complement this analysis. The mooring record shows two events of rapid AW temperature increase in February and August 2004 totaling $0.8\deg$C. Since that the AW temperature record has slowly increased by $0.15\deg$C until September 2005. The data from the 2005 CTD survey downstream of mooring has confirmed that some portions of this warm water have turned along the Lomonosov Ridge toward the North Pole. Upstream along the Laptev Sea continental slope near the Severnaya Zemlia Islands the AW temperature has been found to be relatively high ($2.2\deg$C). However, further upstream in the Kara Sea westward of Cape Arcticheskiy the AW temperature record was much warmer as compared to summer 2004. We hypothesize that the AW temperature increase recorded in the Laptev Sea in 2004 is associated with the AW warm impulse through the Fram Strait in 1999 reported by Schauer at al., 2004. Slightly lowered temperature AW influx into the Arctic Ocean through the Fram Strait has continued until fall of 2000. It suggests that the relatively stable AW temperature observed in the northern Laptev Sea after 2004 warm events continued until September 2005. Our record shows that the next warm AW pulse which passed through Fram Strait in winter of 2000-01 has not yet reached the northern Laptev Sea. It however already results in an extraordinary warming of the AW in the north-eastern Kara Sea. Bases on our estimates and upon previous inferences, these observations suggest that new warm AW impulses are expected in the Laptev Sea and North Pole in the near future.
OS34N-06
The Joint Roles of Tides and Circumbasin Flows Ventilating Atlantic Layer Heat
An Arctic circulation feature, sometimes observed and sometimes inferred from observations (and sometimes modeled), consists of narrow cyclonic boundary currents. In particular this is an advective path for Atlantic Layer heat. Because these currents carry subsurface heat along continental margins (Eurasian, Laptev and Siberian) subject to significant tidal motion, the question arises what role tides play ventilating Atlantic Layer heat. We utilize numerical modeling as tested within the Arctic Ocean Models Intercomnparison Project to examine these joint effects of boundary currents and tides in shelf-basin ventilation of the Arctic. Especially this draws attention to the role of tides hitherto neglected in modeling studies of Arctic climate.