RAPID: Fate of freshwater and heat in the West Greenland Current

The amount of freshwater in the Arctic Ocean has been increasing substantially over the past two decades, and climate projections indicate that this will lead to enhanced transfer of this water southward to the North Atlantic Ocean. At the same time, the meltwater discharge from the Greenland ice sheet has been accelerating over the last 30-years. Both of these sources of freshwater end up in the boundary current that encircles Greenland.

It is imperative to determine the ultimate fate of this water. If it gets fluxed offshore of the boundary current it could impact the large-scale global overturning circulation that helps maintain Earth’s climate. Furthermore, underneath this freshwater, the boundary current carries warm water that originated from the subtropics.

This heat has been implicated in causing basal melt in Greenland’s glaciers – which in turn would lead to more freshwater release. As such, we need to understand how the warm subtropical-origin water makes it to the glaciers. The proposed project is designed to address the pathways and fate of both the freshwater and heat carried in the boundary current along West Greenland.

We will conduct a detailed shipboard survey in Baffin Bay, including measurements along some of the channels leading to west Greenland’s glacial fjords. This is made possible because the US icebreaker Healy is undertaking a rare mission to the eastern sector of the Arctic, allowing for this unique set of measurements. Two contributing studies will be undertaken by collaborators, at no cost to the project.

The first will address the different sources of freshwater using chemical measurements, and the second will shed light the circulation near the fjords using a remotely operated vehicle. A post-doc and three graduate students will participate on the cruise.

An extensive hydrographic/velocity survey will be conducted on the USCGC Healy, from Davis Strait to the northern part of Baffin Bay, to determine the pathways and fate of heat and freshwater that are advected into the region by the West Greenland Current (WGC). The project takes advantage of the fact that Healy will be operating in the eastern Arctic in summer/fall 2021 and is available for a scientific cruise from mid-September to mid-October.

A strategic set of high-resolution sections has been designed to (1) estimate the flux of freshwater from the WGC into the interior; (2) address the two-way exchange of the WGC with the fjords draining several West Greenland glaciers via deep troughs on the shelf; and (3) quantify the structure and evolution of the WGC, as well as the circulation of Baffin Bay to assess its volume, freshwater, and heat budgets. Such a survey has never been done in the study region at small enough station spacing to resolve all of the important currents, with the inclusion of direct velocity measurements, while simultaneously providing the broad coverage necessary to address basin-wide issues.

We will use Healy’s conductivity-temperature-depth (CTD) system, and its hullmounted acoustic Doppler current profilers (ADCPs), along with expendable CTDs to fill in gaps. Two collaborative programs will be carried out at no-cost to the project. The first will measure nutrients and oxygen isotopes to help distinguish the freshwater sources, and the second will deploy a Seaglider to map out warm water pathways and mixing near Jakobshavn glacier. A post-doc and three graduate students will participate on the cruise.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.