State of the Planet

News from the Columbia Climate School

Tracing the Arctic

Leaving Dutch Harbor
The U.S. Coast Guard cutter Healy leaving Dutch Harbor, Alaska, and heading to the high Arctic for the GEOTRACES research cruise. It doesn’t take long to move from a landscape of steep carved cliffs to one of endless waves on an Arctic passage. Photo: T. Kenna

Dutch Harbor Alaska is located on that long spit of land that forms the Aleutian Islands of Western Alaska. Research vessels launch from this location and head northeast into the Bering Sea on their way to the Bering Strait, the gateway to the Arctic.

map of Dutch Harbor
Dutch Harbor, Alaska (from http://www.vacationstogo.com)

Our research cruise is part of the international Arctic GEOTRACES program, which this summer has three separate ships in the Arctic Ocean. The Canadian vessel headed north in early July, and the German vessel will follow a week behind the Healy. Each will be following a different transect in the Arctic Ocean to collect samples. The U.S. vessel has 51 scientists on board, each with a specific sampling program. We will focus our time in the western Arctic, entering at the Chukchi Sea. (Follow the expedition here.)

What is GEOTRACES studying? The program goal is to improve our understanding of ocean chemistry through sampling different trace elements in the ocean waters. Trace elements can be an asset or a liability in the marine system, providing either essential nutrients for biologic productivity, or toxic inputs to a rapidly warming system. This part of the larger program is focused on the Arctic Ocean, the smallest and shallowest of the world’s oceans and the most under siege from climate change. Results from this cruise will contribute to our understanding of the processes at work in the Arctic Ocean, providing both a baseline of contaminants for future comparisons as well as insights into what might be in store for our future.

The land surrounding the Arctic Ocean is like a set of cradling arms, holding the ocean and the sea ice in a circular grasp. Within that cradle is a unique mix of waters, including freshwater from melting glacial ice and large rivers, and a salty mix of relatively warm Atlantic water and cooler Pacific water. Our first sample station lasts over 24 hours and focuses on characterizing the chemistry of the water flowing into the Arctic from the Pacific Ocean. This is critical for locking down  the fluxes and totals of numerous elements in the Arctic.

Map of sea ice
Daily map from the ship showing sea ice cover. Yellow is the marginal ice, and the red is heavy ice. The location of the Healy is visible at the lower edge of the photo at the edge of the red dot.

In the past the “embrace” of the Arctic land has served as a barrier, holding in the sea ice, which is an important feature in the Arctic ecosystem. In 2007, however,  winds drove large blocks of sea ice down the Fram Stait and out of Arctic. In recent years the Arctic sea ice has suffered additional decline, focusing new attention on the resource potential of this ocean.

Unexpectedly this year, the sea ice is projected to be thick along the proposed cruise track, thick enough that it might cause the ship to adjust her sampling plan.

Walrus
Walrus resting on Arctic sea ice. Photo: T. Kenna

The walrus in the above image are taking advantage of the Arctic sea ice. Walrus use the ice to haul out of the water, rest and float to new locations for foraging. Walrus food of preference is mollusks, and they need a lot of them to keep themselves satisfied, eating up to 5,000 a day, using the sea ice as a diving platform. As the ship moves further from shore, we will lose their company.

Margie Turrin is blogging for Tim Kenna, who is reporting from the field as part of the Arctic GEOTRACES, a National Science Foundation-funded project.

For more on the GEOTRACES program, visit the website here.

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