C54A-01 INVITED 16:05h
Sources and Fate of Fresh Water in the Arctic Ocean
There is more evaporation from the Atlantic Ocean than precipitation into it. Excess evaporated water falls as rain into the Pacific Ocean and into river drainage basins, which both feed into the Arctic Ocean and form part of the Polar Mixed Layer. The Polar Mixed Layer also contains sea ice meltwater and water from the Atlantic Ocean. Fresh water flows from the Arctic Ocean via the Canadian Arctic Archipelago and the East Greenland Current and influences deep water formation rate in the Labrador and Nordic seas as well as the salinity of the waters flowing from these regions. It has been speculated that climate change could alter the amount of sea ice meltwater and river runoff flowing from the Arctic Ocean to the deep-water formation regions of the Nordic and Labrador Seas. How water from these sources are distributed within the Arctic Ocean, how they vary, how they affect deep convection, and how they are partitioned into the various pathways to be redistributed in the North Atlantic are fundamental questions to be addressed for a better understanding of climate processes and climate change. Within the Arctic Ocean we identify and trace fresh water using nitrate-phosphate relationships to distinguish Pacific waters from Atlantic waters, salinity to obtain the sum of sea ice meltwater and river runoff water, and total alkalinity to distinguish between the latter. With tracers, we can produce a map of fresh water distributions within the Arctic Ocean and note some variability. We also can trace these waters through the Canadian Arctic Archipelago to Baffin Bay and as far south as the Grand Banks and in the East Greenland Current to south of Denmark Strait.
C54A-02 INVITED 16:25h
Studies of the distribution and mean residence times of freshwater in the Arctic Ocean using stable isotopes of water and tritium/He-3
Arctic freshwater plays a major role in determining the stratification of the water column within the Arctic Ocean, the Nordic seas and parts of the northernmost North Atlantic. Variability in freshwater storage and export from the Arctic Ocean to the formation regions of deep water in the Nordic seas and the North Atlantic contributes to variability in the preconditioning of surface waters that feed deep convection; as well as to salinity variations in large water bodies found in the Nordic seas and the North Atlantic. Thus, knowledge of the Arctic freshwater balance is a precondition for full description and understanding of the driving forces behind deep water formation and its variability in the Nordic seas and the northern North Atlantic. Since the early 1980's stable isotopes of water have been used to separate the individual components contributing to the freshwater balance of the Arctic Ocean. Additionally, transient tracers such as tritium and its decay product, He-3 have been used to estimate the mean residence times of the freshwater stored in the surface layers of the Arctic Ocean. Here we present stable isotope sections and isopycnal distributions and use them, together with nutrient data, to separate freshwater contributed to the upper waters of the Arctic Ocean by meteoric water (mainly river runoff), Pacific inflow through Bering Strait, and sea ice meltwater. Limited repeat sections are used to study temporal variability in the freshwater distribution. Additionally, we apply tritium/He-3 ages to estimate the mean residence times of the freshwater stored in the upper layers of the Arctic Ocean. Finally, we compare the observed freshwater components to model simulations of a (varying) freshwater distribution in the Arctic Ocean.
C54A-03 16:45h
Salinity Trends on the Siberian Shelves
We present an analysis of observed long-term (~100 year) salinity trends on the freshwater-dominated Siberian continental shelves. A multiple regression was performed in the White Sea (WS), the Kara Sea (KS), the Laptev Sea (LS), and the East Siberian Sea (ESS). Since 1930, both the WS and the KS have been freshening, consistent with reports of increasing river discharge over this period. Over the past 20 years, increases in both river discharge and direct precipitation can explain the observed salinity decrease in the WS, but not in the KS. On the other hand, salinity trends in the LS and ESS indicate that ocean circulation plays a dominate role in these areas, where in recent years freshwater has been diverted eastward along the coast, rather than northward towards the deep ocean.
C54A-04 17:00h
The Freshwater Flux to the Arctic via the Bering Strait
The freshwater flux to the Arctic via the Bering Strait has long been estimated at 1670 km$^{3}$/yr, based on an annual transport estimate of 0.8 Sv and a near-bottom mean salinity of 32.5 psu, referenced to 34.8 psu (Aagaard & Carmack, 1989). This is almost a third of the total freshwater input to the Arctic Ocean. We present 3 substantial modifications to this estimate. 1) The Alaskan Coastal Current - mooring data, ship data, and satellite imagery indicate a warm, fresh, generally coastally trapped current is present in the strait for many months of the year. The first year-round in situ measurements of the ca. 10 km wide current, indicate it alone may carry an additional ca. 400 km$^{3}$/yr of freshwater into the Arctic Ocean. 2) Effects of stratification - summer CTD sections suggest near-bottom measurements overestimate the mean salinity by order 0.5 psu, resulting in a ca. 300 km$^{3}$/yr increase in the freshwater flux estimate. 3) Interannual variability - a 13-year time-series of near-bottom moored measurements in the Bering Strait indicates the interannual variability in mean salinity is ca. 0.6 psu, resulting in a variability in the freshwater flux of order 400 km$^{3}$/yr. Combined, these measurements indicate that the prior estimate of 1670 km$^{3}$/yr may be underestimating the actual freshwater flux through the Bering Strait by order 50%.
http://psc.apl.washington.edu/BeringStrait.html
C54A-05 17:15h
Freshwater Fluxes from the Arctic into the North Atlantic Ocean: 1979-2002 Model Results
The recent warming trend in the Arctic region and its future projections has direct implications for this region's hydrological cycle and the global thermohaline circulation. A quantitative analysis of the freshwater export from the Arctic Ocean through the Canadian Arctic Archipelago (CAA) and Fram Strait into the active convection regions of the sub-polar North Atlantic is presented using model output from 1979 to 2002. Results from our pan-Arctic coupled ice-ocean model show that in comparison with the freshwater export through Denmark Strait, the CAA is the major contributor and a direct pathway of freshwater into the northern North Atlantic. The increased freshwater flux through the CAA, found in this study, supports the earlier reports on the significant freshening in the Labrador Sea. This increase in freshwater export from the Arctic is a good indicator of the sea ice cover reduction, which has intensified in the last several years. The consequence of these recent changes on the freshwater export into the North Atlantic is yet to be determined.
C54A-06 17:30h
Future freshwater demands in the Arctic
The overall objective of our research is to understand how humans rely on freshwater at local and regional scales in the Arctic, how these dependencies have changed in the recent past, and how they are likely to change in the future. This study will take place on the Seward Peninsula where climate induced changes in the hydrologic cycle are already being observed. This presentation will describe the human dependencies on freshwater in the Arctic. In particular, we will discuss the effects of inadequate quantity or quality of freshwater on Arctic inhabitants. The freshwater used by humans in the Arctic for drinking, cooking, and washing is derived in many cases from surface water, such as lakes and streams. Since the surface water frozen 6-9 months of the year in the Arctic, communities that rely on rivers and lakes must treat and store large volumes of water for use during winter. The stored water must be heated throughout the winter and distributed on an as-needed basis. Unfortunately, when not enough water can be gathered in the summer or stored in the winter, the entire community may be without freshwater. During these months, water must be collected by individuals from ice, snow, and rain. Collecting water during breakup can be dangerous. River ice is rotten, there is too little snow for snow mobiles, and the tundra is too soft all terrain vehicles. While the state of Alaska and Federal programs are making progress towards developing sustainable water sources for Alaska's Arctic communities, freshwater remains a precious commodity. Communities throughout the Arctic, including Canada and Russia, have similar problems with obtaining and purifying freshwater. As climate induced changes are being observed in the Arctic, the threat to the freshwater resource is now a greater concern than ever. This study is being funded under the NSF Arctic System Science Program, Human Dimensions of the Arctic (OPP-0328686).
C54A-07 17:45h
NSF-ARCSS Freshwater Initiative (FWI): Synthesis as Coordination of Thought to Discover Emergent System Properties
The NSF-ARCSS program is undergoing a purposeful move toward system-wide and synthetic thinking. As part of this broader agenda, the NSF-ARCSS Freshwater Initiative (FWI) is embarking on its own synthesis. FWI synthesis has been organized around two fundamental approaches. The first avenue is a consolidation of existing quantitative information for constructing a comprehensive freshwater budget linking fluxes and stocks through the climate / terrestrial system, oceans, and sea-ice. The second avenue involves linkages of observational studies of paleo, historic, and contemporary water systems and simulation models of their behavior. These efforts represent both inductive and deductive approaches, and the FWI uses an operational definition of synthesis as a coordination of thought to discover emergent system properties to detect and understand Arctic water cycle change. This discussion will focus on recent results of analysis with acknowledgement of input from a broad set of FWI researchers.