Ocean Sciences Meeting Report

Understanding Arctic Ocean Processes Under Changing Ice Cover

Observing Upper-Ocean and Sea-Ice Interactions in the Eastern Arctic Ocean;
Arlington, Virginia, 23–25 April 2014

By Igor Polyakov, Laurence Padman, and Jennifer Katy Hutchings

As Arctic sea ice declines, heat transport into and through the upper ocean plays an increasing role in the highly coupled ­atmosphere-​ice-​­ocean system. The processes by which the ocean affects sea ice are, however, poorly understood. Understanding processes controlling delivery, storage, and release of heat by the Arctic Ocean is an urgent task.

An international interdisciplinary group of scientists met to discuss the next steps in researching Arctic Ocean processes in the context of changing ice cover. This meeting focused on defining key science objectives for an experimental program to advance our understanding of ­atmosphere-​ice-​­ocean interactions. Participants identified, as the overarching goal, development of a comprehensive, quantitative understanding of mechanisms by which the upper ocean regulates fluxes of atmospheric and Atlantic Water heat to the sea ice in the eastern Eurasian Basin (EB) of the Arctic Ocean.

Participants noted that, relative to the more intensively studied Canadian Basin, the EB has a distinct wind regime and upper ocean stratification, younger and more mobile sea ice, a much larger and shallower heat source from the Atlantic Water layer (150–900 meters), and a more energetic internal wave regime due to locally strong tidal currents. Unique EB stratification features include the potential for much larger ­double-​­diffusive fluxes, a deep winter surface mixed layer, and a cold halocline layer providing a barrier between Atlantic Water heat and the upper ocean. Participants concluded that the inability to accurately represent these processes in coupled climate models results in low confidence in the projected transition of the Arctic Ocean to a new climate state as a seasonally ice-free ocean.

Workshop participants noted the need for coordinated, interdisciplinary fieldwork to quantify heat fluxes in the eastern Arctic Ocean and improve understanding of processes by which heat and momentum are exchanged between the atmosphere, ice, and upper ocean and Atlantic Water. This program requires a synergistic combination of different types of observations and technologies (e.g., microstructure vertical profiles coordinated with spatial surveys using autonomous underwater vehicles, multidisciplinary buoys, and ­high-​­resolution aircraft and satellite observations).

The transition from continental slope to ­deep-​­ocean regions was identified as a critical region for setting large-scale ocean heat fluxes; the time dependence of processes acting there (e.g., Atlantic Water transport, tide forcing, eddies, intrusions, and double diffusion) and interactions between them and variable sea ice cover must be understood. Experimental design should use the existing Arctic Observing Network (http://www.nsf.gov/news/news_summ.jsp?cntn_id=109687) and international logistical opportunities (http://​www​.­arcticobserving​.org). The observational program, taking advantage of recent improvements in conceptual understanding and instrumentation, should be closely integrated with modeling efforts to identify needed data sets for developing critical parameterizations.

A white paper summarizing the concept of the experimental program will be drafted by workshop participants, then posted at http://​www​.iarc​.uaf​.edu/​­en/workshops/​2014/​­observations​-in​-­eastern​-­arctic​-­ocean for further community comments before publication. Contact Igor Polyakov ([email protected]) with comments and/or to be included on further communications. This workshop was supported by the National Science Foundation, National Oceanic and Atmospheric Administration, NASA, and Office of Naval ­Research​-­Global.

—Igor Polyakov, International Arctic Research Center, University of Alaska Fairbanks; ­email: [email protected]; Laurence Padman, Earth & Space Research, Corvallis, Oreg.; and Jennifer Hutchings, Oregon State University, Corvallis

© 2014. American Geophysical Union. All rights reserved.