OS13B-0524 1340h
Climatological Annual Cycle of Ocean Oxygen Content
We present estimates of the climatological annual cycle of dissolved oxygen content in the upper 0 to 100 m depth layer of the world ocean. The analysis is based on data from the World Ocean Atlas 2001. The oxygen and heat contents are compared by means of Fourier analysis. The amplitude of the global oxygen and heat contents are dominated by the Pacific Basin in both hemispheres. It is shown that the extra-tropical annual oxygen and heat contents are inversely correlated. The oxygen content cycle lags the heat content cycle by a month. The decadal variability in oxygen is described for the period 1955 to 1998.
OS13B-0525 1340h
Latitudinal and Seasonal Variations in the Atmospheric CO$_{2}$ and O$_{2}$: Results From Shipboard Sampling in the West and North Pacific Ocean
Atmospheric potential oxygen (APO), a tracer defined as a combination of O$_{2}$ and CO$_{2}$ concentration (Stephens et al., 1998), is useful to study air-sea gas exchange related to the physical and biological oceanic processes. This is because air-sea O$_{2}$ and CO$_{2}$ exchanges mainly cause the variation in APO but terrestrial biotic exchanges do not affect it. For example, coupled ocean-atmosphere models predicted equatorial elevation of the annual mean APO. However, this distinct distribution has not been well validated because of the lack of the regular APO observation from the equatorial regions. To investigate the latitudinal distribution of APO, we have collected air samples on board regular service cargo ships between Japan and the United States and between Japan and Australia (or New Zealand) since December 2001. The flask samples were sent back to laboratory in the National Institute for Environmental Studies, and the O$_{2}$/N$_{2}$ ratios and CO$_{2}$ concentrations were determined. We binned the observed data by 10-degree latitude bands, and calculated the average seasonal cycle and deseasonalized trend for each bin. The peak-to-peak amplitude of the average seasonal cycles increased toward high latitude in both hemisphere and its minimum is placed to the about 10-degree north of the equator. The meridional distribution of annual mean APO, showing decreasing gradient toward high latitude in both hemispheres, agrees well with model simulation by Gruber et al., (2001).
OS13B-0526 1340h
Testing Ocean Models with Argon and Nitrogen
Observations of ocean inert gas concentrations have been used to improve understanding of surface ocean oxygen cycling (Spitzer and Jenkins, 1989; Emerson et al. 1995) and gas exchange (Schudlich and Emerson, 1996; Hamme and Emerson, 2002). The interior distribution of these gases may also be useful for testing air-sea exchange and interior circulation estimates from ocean models. This possibility is considered as results from two global ocean model simulations with Ar and N2 as active tracers are compared to in-situ observations at ocean timeseries stations (Hamme and Emerson, 2002). Clear model-data differences are found and discussed in the context of modeled circulation and air-sea gas exchange parameterizations.
OS13B-0527 1340h
Dissolved argon, krypton and xenon demonstrate the importance of rapid cooling in causing gas undersaturations in the deep ocean
The deviation of dissolved inert gases from solubility in the ocean reflects the relative importance of temperature change, diffusive and bubble-mediated gas exchange, atmospheric pressure variation, and ice processes occurring at the ocean surface. In particular, previous results showing that Ar is undersaturated in the deep ocean indicate that deep-water formation creates an imbalance between the rate at which gas saturations are driven downward by rapid cooling and the rate at which gas exchange can bring saturations back toward equilibrium. Here we present depth profiles of argon, krypton and xenon, which were collected at the Hawaii Ocean Time-series station ALOHA in August 2004 and analyzed by a new technique. Gas was extracted from the water by equilibration with a headspace and then gettered to remove interfering gases. Argon was measured by isotope dilution using a $^{38}$Ar spike on a stable isotope ratio mass spectrometer, while Kr and Xe were measured relative to Ar on the same instrument by peak jumping. Precisions of 0.1% were achieved for all three gases based on duplicate samples, while repeated processing and analysis of an air standard demonstrated a laboratory precision of 0.002%. These new measurements show that Kr is even more undersaturated than Ar in the deep ocean. Previous solubility data for Xe appears to be about three percent high, complicating the interpretation of absolute Xe measurements. All three gases reveal small gradients, becoming more undersaturated from 1000 to 4800m, that were undetectable by previous methods. These gradients likely indicate that a difference in the balance between cooling and gas exchange exists between the formation regions of Pacific intermediate waters and Circumpolar Deep Water (CDW). Moreover, the slope of the Ar vs. Kr saturation relationship in this dataset implies that temperature change is the overriding process controlling the Ar/Kr ratio in the ocean.
OS13B-0528 1340h
Argon Isotopes in Seawater: Fractionation During Air-Water Exchange and The $\delta^{40}$Ar of Seawater
We present a status report on a study of the argon 40/36 ratio in seawater. Results from laboratory experiments of the equilibrium and kinetic isotope fractionation factors during air-water exchange are used to interpret initial seawater measurements. Equilibration experiments in which fresh water was incubated with air at constant temperature and pressure resulted in $\delta^{40}$Ar values of 1.05 $\pm$ 0.01 $\permil$ (with respect to air at 25$\deg$ C) and 1.21 $\pm$ 0.01 $\permil$ (2$\deg$ C), which are about 0.4 $\permil$ greater than values for O$_{2}$ and N$_{2}$ but have the same temperature dependence. Kinetic fractionation factor measurements, in which the isotope ratio of pure argon was monitored in the head space of a reaction vessel containing initially gas-free, distilled water, indicate a fractionation factor of -5 $\permil$ during gas exchange - two to four times the values previously determined for O$_{2}$ and N$_{2}$. Initial measurements in the ocean at the Hawaii Ocean Time series indicate surface water values of 1.06 $\pm$ 0.02 $\permil$ (5 m and 23.5$\deg$ C) and 1.12 $\pm$ 0.01 $\permil$ (4000 m and 2$\deg$ C). Surface values are, within error, in equilibrium with the atmosphere, but deep values are 0.1 $\permil$ lighter than expected at equilibrium. It has been shown recently that Ar is undersaturated with respect to atmospheric equilibrium in the deep ocean by 1-2 %. This result is interpreted to be caused by a combination of processes that occur during deep water formation in high-latitude surface waters - rapid cooling leading to undersaturation and bubble formation causing supersaturation. One must know the importance of each mechanism to use the inert gas saturation state as a tracer for deep-water formation processes. Because of the large kinetic isotope fractionation factor, the argon isotope ratio is sensitive to diffusion across the air-water interface and may be used to separate these two mechanisms. We use a simple model to show that a deep water isotope ratio 0.1 $\permil$ lighter than the equilibrium value indicates that the thermally-driven degree of argon undersaturation must be about 50% greater than the measured value. To derive useful interpretation from these data one must be able to make the isotope ratio measurement to an accuracy of $\pm$ 0.01 $\permil$ because of the small differences between the deep water measurements and saturation values. Thus, this initial interpretation will have to be confirmed with more measurements and perhaps a better model.
OS13B-0529 1340h
Mechanisms Controlling the Distribution of Helium and Neon in the Arctic Seas: the Case of the Knipovich Ridge
Helium concentration and isotopic ratio in the ocean are influenced by four sources: the mantle, atmosphere, crust and tritium decay. In addition, the concentration of dissolved gases can be altered by air injection and ice-related mechanisms such as brine rejection, sea-ice melting, and glacial melting, especially in the high-latitude seas. The Knipovich Ridge, a northern continuation of the Mid-Atlantic Ridge (74-$79\deg$N, 6-$8\deg$E), is potentially affected by all the sources and mechanisms mentioned above. This suggests that the ridge should be a good place to investigate these mechanisms. During the Knipovich 2000 expedition, water samples were collected for helium and neon analysis along the axis of the ridge. Although Mn and CH$_{4}$ results suggest the existence of hydrothermal activity in the ridge, we could not detect a significant increase of helium isotopic ratio ($^{3}$He/$^{4}$He) at corresponding water depths. Instead, the bottom waters in the northern section of the ridge were supersaturated by up to 40% for $^{4}$He. The helium isotopic ratio of 1.3$\times$10$^{-6}$ indicates the dominance of atmospheric helium. Using He and Ne saturation anomalies we further explored the mechanisms affecting the distribution of helium and neon in the ridge. Around 5% supersaturation of He and Ne at most deep waters is explained by air injection and brine rejection. However, the large excess in the northern ridge was attributed to the input of 2.5% glacial meltwater, possibly originating from the glacier-covered islands, Svalbard.
OS13B-0530 1340h
Trifluoromethyl Sulfur Pentafloride (SF5CF3), a Gas With Potential for Tracer Release Experiments
SF5CF3 is chemically similar to SF6, a gas which has been used extensively in tracer release experiments, with a CF3 group substituted for a F atom in the molecular structure. It is a gas at atmospheric pressure and is present in the atmosphere with a mixing ratio of 0.12 ppt in 1999 [Sturges et al., Science, 289, 2000]. Sturges et al. (2000) measured a vertical profile of SF5CF3 and SF6 in Antarctic firn ice, showing that it has existed in the atmosphere for the last 3 decades and has increased over time with a trend that nearly parallels the increase of SF6. This suggests that its source could be related to the production and use of SF6, but there are also industrial processes for which it is a by-product. However, the exact source is not understood at this time. SF5CF3 is chemically stable with an estimated atmospheric lifetime of about 800 years [Takahashi et al., Geophys. Res. Lett., 29, 2002]. Because of its very low mixing ratio in the atmosphere and its chemical stability, it has very high potential for use in tracer release experiments. We have carried out some preliminary experiments to evaluate this potential. SF5CF3 can be measured in water samples by the same purge and trap - gas chromatographic procedure used for CFCs, has an ECD sensitivity slightly greater than SF6, and has a linear ECD response up to at least 80 fmoles. A preliminary determination of its solubility in fresh water revealed an Ostwald coefficient of 0.031 at 25 deg C, which is about half that of SF6. Its Ostwald coefficient in 1-octonol was measured to be about 3, roughly 7 times greater than for SF6. This suggests that SF5CF3 will have a greater affinity for organic matter than SF6. In open ocean tracer release experiments, SF6 is slowly transported downward in addition to its vertical spreading by diapycnal mixing. This could be caused by adsorption and release from sinking particles with organic phases, but the solubility of SF6 and SF5CF3 in 1-octanol indicate this effect is too small to account for the transport. We will continue our investigation of the suitability of using SF5CF3 in ocean tracer release experiments by better determining its solubility, determining partition coefficients between seawater and various types of particulate matter, and performing a tracer release experiment in the Santa Monica Basin along with SF6 to directly compare the behavior of these two trace gases.
OS13B-0531 1340h
In-Situ Isotope Ratiometer for Hydrothermal Effluent Analysis
Deep-sea hydrothermal vents provide unique access to water that has been trapped beneath the ocean floor for extended periods of time. Researchers have speculated that a Subsurface Lithotropic Microbiological Ecosystem (SLiME) may exist in this stagnant environment, and therefore desire to study hydrothermal vent effluents for indication of biogenic activity. Specifically, the carbon isotope ratio of methane and carbon dioxide emanating from such vents can provide decisive evidence of such a SLiME. Current technology involves obtaining effluent samples, transporting them from the ocean floor, and examining their degassed constituents with an Isotope Ratio Mass Spectrometer (IRMS). In practice, this procedure has led to contamination and severely limits the number of samples studied. We will report on the development of an in-situ optical analyzer to measure the carbon isotope ratio in both methane and carbon dioxide emanating from deep-sea hydrothermal vents. This analyzer degasses water at high pressure and then employs Off-Axis Integrated Cavity Output Spectroscopy to determine the carbon isotope ratios to better than 0.1%, sufficient to provide evidence of biological activity. Results of preliminary, laboratory testing will be divulged that involved the degassing of gaseous samples and subsequent removal of water vapor and hydrogen sulfide. Final deep-sea packaging and deployment opportunities will also be presented.
OS13B-0532 1340h
Measurement of Relative Dissolved Gas Concentrations Using Underwater Mass Spectrometry
The deployment of underwater mass spectrometer (UMS) systems in marine and lacustrine environments has provided chemical data of exceptional temporal and spatial resolution. UMS instruments operate moored, tethered, remotely, or autonomously, allowing users to customize deployments to suit a wide variety of situations. The ability to collect and analyze real-time data enables prompt, intelligent sampling decisions based on observed analyte distributions. UMS systems can simultaneously detect a wide variety of analytes generated by biological, chemical, physical, geothermal and anthropogenic activities. A polydimethylsiloxane (PDMS) membrane separates the sample-stream from the spectrometer's vacuum chamber. This membrane is selective against water and charged species, yet highly permeable to volatile organic compounds (VOC) and simple gases. Current detection limits for dissolved gases and VOCs are on the order of ppm and ppb respectively. Semi-quantitative proof-of-concept applications have included horizontal mapping of gas gradients, characterization of geothermal vent water, and observation of dissolved gas profiles. Horizontal gradients in dissolved gas concentrations were determined in Lake Maggiore, St Petersburg, Florida. The UMS was positioned on a remotely-guided surface vehicle, and real-time gas concentration data were transmitted to shore via wireless ethernet. Real-time observations allowed intensive sampling of areas with strong gas gradients. Oxygen and CO2 exhibited patchy distributions and their concentrations varied inversely, presumably in response to biological activity. The UMS signal for methane depended on the instrument's proximity to organic rich sediments. Geothermal vent water was characterized while the UMS was deployed in Yellowstone Lake, Wyoming, on a tethered Eastern Oceanics remotely operated vehicle (ROV). Observations of dissolved vent-gas compositions were obtained to depths of 30m. Distinct differences in dissolved vent-gas compositions at different sites point to diverse geothermal conditions beneath the lake. Oxygen concentrations were low at most vents, while hydrogen sulfide, methane and carbon dioxide concentrations were highly variable. Dissolved gas depth profiles were obtained using the UMS system in Saanich Inlet, Canada. Due to degradation of organic material, the inlet's deep water is typically anoxic, and rich in methane, carbon dioxide, and reduced sulfur compounds. Relative gas concentrations were obtained between the surface and 200m. A thermocline was detected as the instrument entered anoxic bottom water at 100m. Below this depth oxygen signal intensity declined sharply to background levels. In contrast, carbon dioxide increased sharply below 100m until a reproducible maximum was observed at 120m. Methane and hydrogen sulfide increased steadily with depth below 100 m, and exhibited no local maxima. Fully quantitative UMS measurements require characterization of the influence of salinity, and especially temperature and pressure, on the performance of the internal PDMS membrane. Temperature exerts a strong influence on gas diffusion across the PDMS membrane and the behavior of residual gases in the vacuum chamber; therefore, precise thermostating methods must be adopted. Other technical issues being examined in the laboratory include variations in UMS response attributable to pressure-induced membrane compression, and variable hydrodynamic conditions at the sample/membrane boundary. Experiments are being developed to address the issue of calibrating the ion signal intensity for dissolved gas concentrations.
http://cot.marine.usf.edu/hems/underwater/
OS13B-0533 1340h
Prediction of Gas Exchange Rate Using Microwave Backscatter From the Ocean Surface
Radar backscatter from the surface of the ocean is proving to be useful in establishing a relationship between sea surface roughness and gas transfer velocity. This is possible because radar wavelengths fall in the same centimetric range as surface waves that promote near surface turbulence that drives gas exchange. We have established two algorithms that link a field-based relationship between gas transfer velocity and mean square slope of the capillary wave field to a relationship between mean square slope and radar backscatter. The first algorithm exploits specular scattering of altimeter microwave pulses by the sea surface. The second algorithm involves Bragg scattering of microwave signals from a scatterometer. We will briefly review these algorithms, their uses and drawbacks, and insights they provide about the global distribution of gas transfer velocity.
OS13B-0534 1340h
Porewater Profiles of Dissolved N$_{2}$/Ar Gas Ratios in Sediments From the Gulf of Mexico Continental Margin
Dissolved gases in sediment porewaters are useful tracers of the biogeochemical processes that consume organic matter. In autumn of 2003, we collected cores from three stations off the Gulf coast of Texas. The stations ranged from 200 to 1300 meters water depth and represent a range in oxygen exposure time, organic carbon flux to the seafloor, and sediment redox conditions. Porewater profiles of O$_{2}$, NO$_{3}$, NH$_{4}$, and the N$_{2}$/Ar gas ratio were determined at each station. Porewater dissolved O$_{2}$ concentrations decreased rapidly at shallow stations and more slowly at deeper stations; penetration depths ranged from $\sim$5mm at the 200 m station to $\sim$40 mm at the 1300 m station. Nitrate concentrations showed a similar pattern (although over a longer depth scale) with penetration depths ranging from 1.25 cm at the shallow station to 40 cm at the deepest station. We present high-resolution profiles of the porewater N$_{2}$/Ar gas ratio measured in the field by membrane-inlet mass spectrometry (MIMS) using a probe-style inlet. Changes in the N$_{2}$/Ar gas ratio reflect the production of N$_{2}$ gas due to denitrification in the sediments. At all stations the N$_{2}$/Ar gas ratios increased significantly with depth in the sediments and were oversaturated relative to the bottom water N$_{2}$/Ar ratio. The gas ratio profiles increased rapidly with depth as oxygen concentrations went to zero, and maximum values of N$_{2}$/Ar oversaturation occurred at the depth range where NO$_{3}$ concentrations decreased rapidly and thus NO$_{3}$ consumption rates were highest. The maximum in the N$_{2}$/Ar gas ratio occurred at 25 mm at the 200 m station and at more than 70 mm at the 1300 m station, similar to the patterns in the O$_{2}$ and NO$_{3}$ penetration depths. These porewater dissolved gas ratio profiles provide an additional estimate of the total denitrification rate in sediments that can be compared to rates determined from benthic chamber fluxes and NO$_{3}$ profiles.
OS13B-0535 1340h
Constraining Oceanic N$_2$O Production Mechanisms by an Inversion of Large-Scale Oceanic N$_2$O Data
The ocean is a main source of atmospheric N$_2$O, an important greenhouse gas with a high global warming potential (GWP). N$_2$O is produced in the ocean through two pathways: one is associated with nitrification, i.e. the conversion of ammonium to nitrate during the remineralization of organic nitrogen; the other is associated with low oxygen concentration and likely involves a not well understood coupling between nitrification and denitrification. We refer to the latter as the low oxygen pathway. These two mechanisms have very different characteristics. The nitrification pathway occurs throughout the ocean in the main thermocline and has a yield of only about 1 in 1000, i.e. 1 molecule of N$_2$O is produced per thousand molecules of NH$_4$ entering nitrification. In contrast, the low oxygen pathway has very high yields, but occurs only in a few low oxygen regions located mainly in the tropics and in coastal ocean. These differences result in the two mechanisms having very different responses to environmental changes. For example, Jin and Gruber (2003) showed recently that the two different mechanisms lead to very different offsetting effects when the ocean is fertilized with iron to reduce atmospheric CO$_2$. However, the relative importance of these two mechanisms is still not well known. We model these two mechanisms separately in a global-scale biogeochemical model into which we have added the N$_2$O cycle based on the work of Suntharalingam et al.(2000). We then constrain the relative importance by using inversion methods, taking advantage of a new global data-set of oceanic N$_2$O observations. Our initial results show that about half of the N$_2$O in the ocean is produced by nitrification pathway and the other half by the low oxygen pathway.
OS13B-0536 1340h
Modeling the Distribution and $\delta$$^{15}$N of Nitrogen Gas and Nitrogen Species in the Black Sea
We have measured the distributions of NO$_{3}$, NO$_{2}$, NH$_{4}$, N$_{2}$ and PON and their $\delta$$^{15}$N values in the Black Sea in order to unravel the cycling of nitrogen, especially the role of anammox (NO$_{2}$$^{-}$ + NH$_{4}$$^{+}$ = N$_{2}$). In conjunction with these measurements we have constructed a coupled physical-biogeochemical model of the water column. The physical model is a vertical transport model that includes simulation of entrainment and intrusions from the Bosporus Plume. This model has been calibrated using the historical record of Cs-137 measurements. The biogeochemical model includes mass balance equations for $^{14}$N and $^{15}$N. The main features and possible explanations from the model runs include: 1. Values of $\delta$$^{15}$N-N$_{2}$ are low ($\sim$0.5 per mil) compared with $\delta$$^{15}$N for NO$_{3}$, NH$_{4}$ and PON ($\sim$8 per mil) because a significant fraction of NO#_{3}$ must be reduced to NH$_{4}$ rather than N$_{2}$. 2. $\delta$$^{15}$N-NO$_{3}$ is constant (and unusually high) in the oxic layer ($\sim$8 per mil) then increases sharply towards the onset of sulfide. This must result from the anammox reaction that takes place in the suboxic layer. 3. $\delta$$^{15}$N-NH$_{4}$ is low in the deep water ($\sim$2 per mil) and increases toward the onset of H$_{2}$S. This must be the result of reduction of NO$_{3}$ to NH$_{4}$ when NO$_{3}$ in the Bosporus Plume intrusions reacts with H$_{2}$S. 4. $\delta$$^{15}$N-PON remains constant ($\sim$7 per mil) in the oxic layer, increases to a small maximum ($\sim$9 per mil) at the top of the suboxic zone and then decreases to 3 per mil in the sulfide layer. These distributions reflect oxidation of NH $_{4}$ and bacterial production from DON and NH$_{4}$.
OS13B-0537 1340h
Radiocarbon in Surface Waters of the Gulf of Mexico and Caribbean as Recorded in Hermatypic Corals
Radiocarbon measurements of hermatypic corals from near the Cariaco Basin and Veracruz, Mexico are used to reconstruct the D14C of surface waters in the Caribbean Sea and western Gulf of Mexico. These results will be used to investigate the carbon flux from the atmosphere into the ocean in these regions. Coral chronology was resolved using x-radiography to determine annual density bands deposited during the warm summer months. Sub-annual and annual samples were obtained from 1943-1996 using a microdrill and radiocarbon composition was determined using accelerator mass spectrometry. The corals were sampled at annual intervals from 1945-1955 and average values from the two sites are similar (-52 $\pm$4 per mil at Veracruz and -53 $\pm$3 per mil at Cariaco). Due to the production of 14C as a consequence of nuclear weapons atmospheric tests in the 1950s and 1960s, the D14C in the coral skeletal material began increasing in the late 1950s and reached a maximum in 1978 of 165 $\pm$4 per mil at Veracruz and 127 $\pm$3 per mil in 1973 at Cariaco Basin. These data and additional radiocarbon measurements of corals from the Flower Garden Banks (northern Gulf of Mexico) and published data from the region will be used to investigate the processes controlling radiocarbon concentrations in the surface waters of the Caribbean Sea and Gulf of Mexico.
OS13B-0538 1340h
Factors Affecting the Temporal and Spatial Variability and Characteristics of Marine Hydrocarbon Seepage, Coal Oil Point, CA
The Coal Oil Point (COP) natural marine hydrocarbon (HC) seep field of the Santa Barbara Channel is one of the largest and most intensively studied marine HC seepage regions. Daily oil emissions were estimated at $\sim$100 barrels, while total gas emissions reach $\sim$100,000 m$^{3}$day$^{-1}$. The COP seep field consists of several intense areas of seepage that are each made up of dozens to hundreds or thousands of individual vents. Observations show that COP seepage varies spatially (cm-km), temporally (second - decade), and in magnitude (from trace to 10$^{4}$ m$^{3}$day$^{-1}$). The primary seepage trends (scale of 100s-1000s meters) lie above major WNW-ESE faults cutting the Coal Oil Point and South Ellwood anticlines. There is significant variation in seepage along these trends with the most intense emissions at intersections with NE-SW cross-cutting faults. Spatial variations on shorter scales (10s of meters) are related to fractures, exposed shale beds, and seabed characteristics (pebbles, sand, tar, etc.). Individual vent distribution varies on sub-meter scales. Seabed characteristics, seepage spatial distribution, and gas and oil emissions relate to seabed and subsurface geologic features. For example, bubble sizes are correlated with the substrate from which they are emitted. Small-sized bubbles ($<$0.1 cm diameter) emerge directly from fractures in the exposed shale. Larger-sized bubbles (0.1 $<$ 1.0 cm) tend to escape after passing through a sediment overburden, with the size of the bubbles increasing with the sediment coarseness. Giant bubbles ($>$1.0 cm) are associated with a tar-sand overburden. The bubble size is an important factor with regards to bubble-mediated transport of seep gas and oil to the sea surface. A network of small conical tents was developed and deployed in active seep areas to gather high time resolution (0.2 s) gas emission rates that also had high spatial resolution (1 m). The tents ($\sim$1-m tall, $\sim$2-m diameter) sit directly on the seabed over areas of seepage, typically spanning several vents. Rising bubbles generate an upwelling flow of water that spins a turbine with an optical encoder on its axis. The encoders are connected to a multi-channel datalogger. Measurements are recorded in revolutions per second and converted to gas volume flux based on laboratory calibration. Spectra of the seepage time series showed the effect of external forcings, including swell and tides. Responses to external forcing factors, such as a 1% swell variation, differ between multiple tents. Seeps with a higher flux exhibit a smaller response than seeps with a lower flux. Flux variations between tents demonstrate the complexity of the underlying processes of gas, oil, and tar migration through an inter-connected subsurface fracture network.