Unit Affiliation: Geochemistry, Lamont-Doherty Earth Observatory (LDEO)
Non-technical: The salinity of water in the Arctic Ocean determines much of its buoyancy and thus how stable the various layers of water are. This is important because stability of the stratification of the ocean determines its circulation, heat transport and formation of deep water, which in turn affect the local and regional climate system, as well as ocean/atmosphere/climate interaction in lower latitudes. Thus understanding the basic processes of the circulation, buildup, and release of lower salinity water (called 'freshwater') is of fundamental importance for understanding future states of the Arctic Ocean. This project will study the dynamics and variability of the freshwater components and the overall freshwater inventories, in the region of the ocean north of Greenland, where water and sea ice ultimately take one of two pathways south. The main goal of the study is to understand how buoyancy is redistributed within the Arctic Ocean and how freshwater accumulates and is released. The project is especially interested in the role distinct freshwater components play in this process. For this purpose data collected as part of the Arctic Observing Network will be compared to model simulations and vice versa to test hypotheses concerning the circulation, accumulation and release of freshwater and its components in the Arctic Ocean and to test the performance of an Arctic Ocean model. This project will create data products for researchers and educators interested in the Arctic and its response to climate change. Circulation patterns of the individual freshwater components and other synthesized outputs, along with information and documentation needed to assist educators, will be made publicly available through an online site that is expected to have significant traffic from educators in academia and secondary school levels. This project will provide the core of a PhD dissertation for a graduate student. Technical: Understanding the basic processes of the circulation, buildup, and release of freshwater is of fundamental importance for examining possible future scenarios of the freshwater lens covering the Arctic Ocean, the role of freshwater in internal circulation within the Arctic, and the role of freshwater in deep water formation in the convective regions of the Nordic seas and the North Atlantic. This project will study the dynamics and variability of the freshwater components and the overall freshwater inventories, in the Switchyard (SY) region in the context of an Arctic Ocean-wide analysis of freshwater component sources and pathways. The main goal of the study is to understand how buoyancy is redistributed within the Arctic Ocean and how freshwater accumulates and is released. There will be special emphasis on the role distinct freshwater components play in this process. Recent long-term observations conducted in the Switchyard (SY) region as part of the Arctic Observing Network (AON) program, have revealed detailed information on both the total freshwater balance, and the components contributing to it: Pacific Water (PW), Meteoric Water (MW: River Runoff and P-E), and Sea Ice Meltwater (SIMW). The SY observations along a section between Alert and the North Pole show rapid changes in the contributions of individual freshwater components to the total inventory along with gradual changes in the total freshwater content. From backtracking the surface circulation in time based on sea ice drift patterns, the group infers that the rapid changes in the freshwater components are probably due to shifts in the sea ice and surface water source regions and pathways on time scales as short as one year, the frequency of their observations. This project will combine the SY freshwater component data with those from previous (icebreaker) expeditions to characterize the main features of their distributions. In a second step, the team will extend the sea ice tracking method developed by Maslanik and Fowler to include Ekman transport in the surface ocean and will download GCM runs that simulate individual FW components. They will track the observed freshwater components back to their source regions, and forward to their exit points from the Arctic, and will identify mechanisms impacting the freshwater component circulation, especially in the SY region where they have an 8-year time series. The principal intellectual contributions will come from integrating observed freshwater component inventories and pathways with those obtained from model simulations, inferring the dynamics governing the freshwater component distributions and their adjustment as functions of source terms and atmospheric forcing.