Intellectual Merit: The fresh, buoyant currents which travel along the topographic margins from the polar to the subpolar regions have a profound influence on both the regional and global climate. They also have a strong impact on the ecosystems and fisheries downstream by affecting nutrient supply to the surface layer. Yet our knowledge of how distinct freshwater inputs in the polar basins and coastal regions are transformed into the variable, fresh flow observed downstream is limited. Identifying and understanding the processes that govern this transformation is even more pressing at a time when there is increased freshwater export from the Arctic and models predict an even greater export in the future. The opportunity to study the transformation of a large riverine input, from multiple rivers, combined with the inflow of Arctic freshwater, in a semi-enclosed basin connected to the large scale ocean through a strait is provided by new moored data from Hudson Strait. Hudson Strait is the third largest contributor of freshwater to the North Atlantic and a major contributor of fresh water to the Labrador Current, whose waters influence the shelf-slope waters of the entire northeastern North American coast. Its outflow is strongly varying on daily to interannual timescales. Amongst the potential sources of this variability are the spatially and temporally distributed runoff sources, local forcing and remote atmospheric forcing and variations in the inflow from Davis Strait. The goal of the work proposed is to: (1) identify the processes influencing the freshwater transport on daily to interannual timescales, and (2) determine the relationship between the transport and river run-off, the Davis Strait transport and the Labrador Current transport. These goals will be achieved through the analysis of new and historical moored and hydrographic data from Hudson Strait, complemented by meteorological data, river data and a regional numerical model run by one of our Canadian colleagues. The results from this study will not only improve our knowledge of the freshwater pathways west of Greenland but, also, augment our general understanding of the processes that transform freshwater on its route to the subpolar regions.
Broader Impacts: This work is not only of relevance to global climate and to the northeastern North American coast, but it is equally important for the region upstream of the strait which supports a large native population and diverse ecosystem and that has been identified as one particularly susceptible to climate change. The proposed work will foster international collaborations and those across disciplines and bridge the gap between the polar and subpolar regions. The project will involve a post-doc, a U.S. and a Canadian graduate student who will benefit from the exposure to a diverse, international group of scientists. As part of the proposed work we have initiated a collaboration with an accomplished writer with a background in Arctic exploration and Inuit culture. An immediate result of this collaboration is a series of lectures to be conducted in museums around the U.S. that will compare and contrast scientific and geographic exploration by exploiting the 400 year anniversary of Henry Hudson's voyage into Hudson Strait and Bay. Future plans include articles in natural history/popular science magazines and a series of lectures in the Inuit communities along the shores of Hudson Bay and Strait.
Fresh, light waters travel long distances along the topographic margins from the polar to the subpolar regions. These buoyant currents have a profound influence on both the regional and global climate because of their intrinsically large vertical stability. They also have a strong impact on the ecosystems and fisheries downstream by affecting nutrient supply to the surface layer. Yet our knowledge of how distinct freshwater inputs in the polar basins and coastal regions are transformed into the variable, buoyant currents that flow along the margins of large oceanic basins is limited. Identifying and understanding the dynamics and processes that govern this transformation is the focus of the work proposed here. This question is even more pressing at a time when there is increased freshwater export from the Arctic and models predict an even greater export in the future. This project has focused on one of the major pathways through which freshwater enters the North Atlantic. Almost all of the river water from the Northern US and Canada, east of the Rockies, is eventually discharged into Hudson Bay - a shallow inland sea that, as a result of the large riverine input - is exceedingly fresh. From here the water eventually emerges into the ocean through Hudson Strait a large channel connecting Hudson Bay to the Labrador Sea. Once in the Labrador Sea, the freshwater flows southward along the northeast seaboard - where it has a big impact on the local ecosystems and dynamics. In this study, a number of oceanographers, hydrologists and atmospheric scientists worked together both to quantify the export of freshwater from Hudson Strait and what controls its variability. We analyzed data collected through a US-Canadian collaboration in Hudson Strait and used several models to understand how the river input into Hudson Bay eventually translates into freshwater discharge into the Labrador Sea. We found that the link is far from simple. On timescales of days, the export is modulated by storms passing over Hudson Bay which allow the episodic release of freshwater. On seasonal timescales, the release is modulated by winds over Hudson Bay, by the river discharge and by the seasonal sea-ice cover over Hudson Bay. On interannual timescales, the release is governed by the storage and release of freshwater from the large Hudson Bay system - largely modulated by large scale atmospheric forcing. As part of this project we also collaborated with a historian, Larry Millman, to investigate the parallels between our modern day exploration of Hudson Strait and that of Henry Hudson, about 400 years ago. Henry Hudson sailed into Hudson Strait aboard the Discovery from Great Britain in 1610, looking for the Northwest Passage. The ship remained trapped in sea ice in Hudson Stait and had to overwinter there. In the spring of 2011, the ship was able to finally break free again and Capt. Hudson pressed his crew to continue into Hudson Bay. Eventually, a disagreement on whether to continue or not led to mutiny and Hudson, his son and a few other crew members were left adrift on a small boat and were never seen again. This story and its parallels to our efforts to collect measurements from this remote and challenging environment have been told in a Radio Piece that has been airing on Living on Earth (NPR) - www.pri.org/stories/2014-06-16/todays-arctic-explorers-follow-footsteps-history.
