OS43B-1235
Investigating methods of wave-ice interactions
Our study investigates methods of capturing wave-ice interactions in non-continuous sea-ice cover situations. Wave-ice interactions occur in the Arctic marginal seas where concentrations are less than 100% and individual ice floes and pancake ice are present. The concentration of ice floes directly affects the sea state by acting to filter wave energy. Since many existing wave models do not consider sea ice, these wave models do not accurately portray wave energy in marginal sea ice zones. For engineering considerations in the Arctic coastal zones, however, it is important to consider the influence of floating ice to more accurately describe wave propagation. We look into the work that has been done by such authors as Squire (2007) and Ogasawara and Sakai (2006). We also explore the boundary element method and the finite element method to analyze wave-ice interactions.
OS43B-1236
Variational estimate of the volume transport through the Kamchatka Strait and Aleutian passes.
The quasistationary climatological Bering Sea circulation is reconstructed as a variational inverse of the hydrographic (temperature/salinity) and atmospheric climatologies, transport estimates through the Bering Strait, and data from approximately 500 surface drifters. Our results provide the estimates of the mean volume transport through the Kamchatka Strait of 28-30 Sv, Near Strait transport of 12-14 Sv, and quantify the throughflow in other Aleutian passes. The obtained transport estimates are significantly higher than the geostrophic estimates based on the assumption of the level of no motion at the depth of 1000 or 1500m, which can be found in the literature. The results reveal that the transports in the Kamchatka and Near Straits experience significant seasonal variability of approximately 10 Sv and 3-4 Sv respectively. The new estimates of the volume balance of the Bering Sea are in agreement with the recent measurements of the high inflow into the Bering Sea through the Amukta Pass and velocity observation at 1000 m with ARGO drifters. We speculate, that the revealed enhanced water exchange can be very important for the export of the different biological and chemical tracers into the Bering Sea.
OS43B-1237
Sustaining the Bering Ecosystem: A Social Science Research Plan
The Bering Sea is changing from an ice-dominated to an increasingly open water system. The over-arching goal of the NSF-supported Bering Ecosystem Study (BEST) is to understand the effects of climate variability and change on the Bering Sea ecosystem. To the people who are simultaneously a part of that ecosystem and rely on its productivity for life and work, climate change and its effects are among the top concerns. Sustaining the Bering Ecosystem articulates a vision and approaches for social science research as a component of the BEST Program (www.arcus.org/bering). This science plan seeks to initiate research to elucidate the dynamic relationship between the Bering Sea ecosystem and the humans who constitute an integral component of that system. To do so, this plan delineates a research program focused on three broad themes: 1. Impacts on humans: how past, current, and possible future changes in the Bering Sea ecosystem affect the health and well-being of people living and depending on this region for subsistence, employment, and cultural survival. 2. Human impacts: how changing human uses of the Bering Sea region affect the natural cycles of this ecosystem by moderating and/or accelerating systemic changes. 3. Dynamics of human and non-human natural systems: how the human-environmental dynamic has changed through time and may change in the future due to internal and external opportunities and pressures. These themes are developed in the context of a community-driven approach based on the concerns, goals, and interests of Bering Sea residents and other stakeholders of the region. This plan has been drafted through the collaboration of Bering Sea residents (primarily Alaska Natives) and non-resident stakeholders, social scientists, and natural scientists to focus efforts around research questions important to stakeholders, which in various ways center on issues of sustainability (of resources, economic opportunities, ways of life, and culture itself). The research envisioned by this plan will provide a foundation for resident communities, regional corporations and tribal councils, industry stakeholders, resource managers and policy makers at various levels to plan for and face the future with less uncertainty. To accomplish this goal, research must be developed with attention to concrete and practical outcomes. In this social science effort, and in the broader Bering Sea Ecosystem Study (BEST) of which it is a part, synergies must be explored that harness the strengths of multiple disciplines toward common purposes. For this reason, the research anticipated in this plan will: - generally involve interdisciplinary teams and projects that include a modeling component; - may focus on more than one of the defined research themes; and - require collaboration and partnership with Native and non-Native residents and stakeholders in the Bering Sea. http://www.arcus.org/bering
OS43B-1238
Variational Reconstruction of the Chukchi Sea Circulation in October-November 1990
We present the results of variational hindcast of the circulation in the Chukchi Sea in October-November 1990. The optimal solution of the primitive equation model of the Chukchi Sea is obtained by 4dvar assimilation of the data of several hydrophysical surveys in the region combined with the CTD and current meter records from 11 moorings. NCEP/NCAR atmospheric data and hydrographic climatologies were used as background data to ensure the well-posedness of the data assimilation problem. The model solution is controlled by initial conditions, fluxes through the open boundaries, and surface fluxes. The first guess model solution is obtained by 3dvar optimization of the initial conditions and boundary fluxes in the quasi-stationary version of the model. The obtained optimal solution is consistent with the observations and data error statistics. The observations constrain well the model solution in the Bering Strait region, while the model dynamics allows us to reconstruct the path of the Bering Strait water in the Chukchi Sea. The data assimilation results provide robust quantitative estimates of the fresh water transports in the Chukchi Sea and improve the prior estimates of the ice-ocean fluxes in the region. The circulation pattern reveals periodical reverse of the East Siberian Current and the Bering Strait throughflow.
OS43B-1239
Pressure ridge induced sea water infiltration in a porous first year sea ice bottom layer.
Heat exchanges at the ice–ocean interface are key to ocean-ice-atmosphere models. At spring when the brine channel network re-opens and allows water to penetrate and exit the bottom ice layer, pressure gradients induced downstream of pressure ridges act as an heat pump that extract latent heat from the ice body. We present results of a prognostic simulation of the volume melt that occurs in the bottom part of the ice cover as a consequence of a forced sea water infiltration. Momentum, mass and heat equations are solved within the ice using a finite difference model. Non-linear equations within each cell are implemented to include volume melt in the thermodynamic equilibrium of the ice cover. The ice is modeled as a porous matrix which walls melt with time allowing to monitor the evolution of the ice porosity. Results present temperature salinity and porosity time series in the affected part of the ice. We also compute the heat balance fluxes involved in the process.
OS43B-1240
Seeking the True Antarctic Ocean
With World Ocean warming a corrected name use is recommend with a universal adoption of the name, "Antarctic Ocean. This one large body of circumpolar water lies adjacent to - and south of - the Antarctic Convergence, on its northern perimeter, and is bordered to the south by the shoreline of the Antarctic continent. The Antarctic Ocean has a distinct water mass, with a true perimeter, and with a homogeneity, comprizing a unique environment for a specialized flora and fauna. It is recognized generally by its surface waters, ranging from 3.5 - 4.5 degrees Celsius (summer) and one degree C (winter).While its northern boundary, ' The Antarctic Convergence', has a water quality and thermal difference, this polar front is continuous and circumpolar, and it abuts -- and streams along with -- the ultimate southern extremities of the Atlantic, Pacific and Indian Ocean waters. Parameters, characteristics and dynamics of water exchange are considered, here, with some water exchanges, with Intermediate and Antarctic Bottom water noted. It maintains its own forceful 'West Wind Drift', a current driven and emboldened by Earth's Geostrophic West Wind. Features defining the Antarctic Ocean: (1)Washing all shores of the continent named Antarctica; it is .the only ocean reaching this Antarctic Continent.; (2) it is one of Earth's two Polar (and coldest) oceans, the other, named Arctic Ocean, of which it is the opposite (the Anti); (3) its distinctive cold waters of the Antarctic Ocean and its peripheral seas, floating ice tongues, the frigid stamp of Antarctica's continental glaciers and ice fields; (4) the Antarctic Continent is the source of continual replenishment from her ice cap and melt-water derived from the great mountains, valleys and the massive polar dome of ice. Further, in the literature the present usage, 'Southern Ocean', by some authors, confuses the true Antarctic environmental waters (i.e. south of - and within the South Polar Front - Convergence) with southern ocean waters, that extend farther northward, beyond the convergence, to the 60th parallel of S. latitude. Conclusions of this paper thus deal with clarifying existing vaguaries and apparent inappropriate usage of name and designations. This gives us a more definitive geographic-ecologic area than has been commonly recognized, and clarifies the procedure of testing for ocean change with global warming.
OS43B-1241
Enrichment of nitrous oxide in water column of Bering sea and Chukchi sea
While dissolved N2O is close to equilibrium with the atmosphere at surface in wide area of open ocean, significant enrichment were found in the upwelling region having pronounced oxygen-depleted water at subsurface, such as Arabian sea and off northern Chile. Both Bering sea and Chukchi sea area, fully oxygenated in the water column, have been characterized by low DIN/DIP, probably caused by denitrification in the sediment (e.g. Rowe and Phoel, 1992). Because N2O is a intermediate product of denitrification, such DIN decomposition can produce N2O in the area. To test this hypothesis, samples of both sea water and pore water were collected from 23 sites in the area to determine both concentrations and stable isotopic compositions of N2O (δ15N and δ18O), during R/V Mirai (JAMSTEC) MR06-04 cruise. We found significant accumulation of dissolved N2O in both surface and subsurface water column shallower than 50m, with concentrations up to 25.1nM. The annual emission rates of N2O to the atmosphere can be estimated to be 0.06 - 0.36 Tg N yr-1 in the area. It turns out that the N2O enriched water mass can be characterized by low DIN/DIP ratios. Furthermore, the accumulated excess N2O can be characterized by both 15N-depletion and 18O-enrichment relative to atmospheric N2O. It is difficult to assume nitrification in the water column for the source of the excess N2O. We conclude that the excess N2O in both Bering sea and Chukchi sea had been produced through denitrification in the sediment.
OS43B-1242
Seasonality in the Response of Sea Ice to Wind Forcing on the Mackenzie Shelf, Arctic Ocean , and Consequences to Upwelling Under the Scenario of Climate Warming
Seasonal pattern of ice motion in response to wind forcing and potential consequences to upwelling on the Mackenzie Shelf are considered using satellite-derived ice motion data from the National Snow and Ice Data Center and the NCEP 10 m wind data. The frequency of strong upwelling-favorable alongshore ice motion is high in early winter (November and December) compared to middle and late winter (January to May). For periods when the alongshore component of the wind is upwelling-favorable, the ratio of ice drift divided by wind speed on the Mackenzie Shelf is 0.024 in November and 0.008 in March; we conjecture that this ratio decreases as winter progresses because the internal ice stress becomes stronger as both ice thickness and ice concentration increase. This constitutes a possible 10-fold decrease in the seasonal transmission of wind stress to the underlying water from November to March. Conversely, this ratio in May (0.015) is higher than that in March. We suggest that it is because the internal ice stress becomes weaker as ice concentration decreases on the Mackenzie Shelf in May. Hence, under the same wind forcing, the potential for winter upwelling on Mackenzie Shelf may be enhanced if climate warming results in reduced ice thickness and/or ice concentration. A major unknown remains the effective coupling of wind to water as ice concentration and relative roughness decrease.