Margaret McCall

Advisor: Mary-Louise Timmermans


The likely status of the Arctic Ocean as both an indicator and an instigator of climate variability make it an extremely worthwhile object of study. The Arctic, defined as the region north of the Arctic Circle (66.5°N), is an extraordinarily complex system marked by tightly coupled ocean-atmosphere-ice-land interactions. Though the definition of the Arctic Ocean is somewhat contentious, it occupies most of the area between 70°N and the North Pole and is characterized by its cover of floating sea ice. This sea ice, which reaches its maximum cover in March and its minimum in September, is composed of individual floes in constant motion. The current present in much of the central Arctic Ocean, which carries sea ice clockwise around the Canadian Basin, is called the Beaufort Gyre. Arctic sea ice floats atop a layer cake of water masses: the ice overlies relatively fresh water, which overlies water from the Pacific, which overlies warm water from the Atlantic, which overlies deep water. The salinity differences between these water masses create a stable stratification in the upper Arctic Ocean. It has been argued that changes in the character of these water masses have contributed to a recent dramatic retreat in the Arctic sea ice cover.

Frustratingly, this ice pack has presented scientists with important questions to answer about the Arctic Ocean while significantly impeding data acquisition. The 2004 advent of the ice-tethered profiler (ITP), however, has proven extremely valuable in gathering information from beneath the ice to great depths. ITPs are set up as follows: on top of the ice pack sits a surface capsule with a tether extending below it through the ice. The tether (weighted at the end to keep it vertical) is between 500 and 800 meters long; a cylindrical instrument attached to the tether cycles vertically, carrying oceanographic sensors through the water column. The principal data gathered, which are transmitted to shore in near-real time, concern conductivity, temperature, and depth. Over its three-year lifetime, each ITP returns two high-vertical-resolution profiles of the upper Arctic Ocean per day. On the whole, information collected with ITPs promises to provide important fresh insights on the nature of the Arctic Ocean system.

For my senior thesis, I plan to analyze ITP profiles to investigate one or several of various phenomena; including heat transport associated with warm Arctic Ocean eddies and changes in the distribution of warm water originating in the Pacific Ocean. The importance of this project lies in the impact of heat transport on Arctic sea ice cover. Eddies come in various classes in the upper ocean and are particularly prevalent in the Beaufort Sea. By understanding the distribution of the different classes of eddies, I hope to learn about their formation process. Additionally, water of Pacific origin is often transported great distances in the Arctic Ocean in the form of Pacific Water eddies. Thus, using ITP profiles to come to an understanding of the formation and distribution of different types of eddies would shed light on their function in heat transfer in the Arctic Ocean. Finally, water that comes from the Pacific Ocean is notable for its role in bringing fresh water and near-surface heat to the Arctic, two factors that strongly impact the presence of sea ice. An assessment of how the properties and distribution of the Pacific water have changed since 2004 (the beginning of ITP measurements) could lend insight about recent changes in Arctic sea ice cover.