Changes in the Thickness and Circulation of Multiyear Ice in the Beaufort Gyre Determined From Pseudo‐Lagrangian Methods from 2003–2015. Issue 8 (9th August 2019)

• Record Type: Journal Article
• Authors: Mahoney, Andrew R.; Hutchings, Jennifer K.; Eicken, Hajo; Haas, Christian
• Is Part Of: Journal of geophysical research. Volume 124:Issue 8(2019)
• Page Start: 5618
• Page End: 5633
• Publication Date: 2019-08-09
• Subjects: sea ice -- Beaufort Gyre -- ice thickness -- Arctic -- multiyear ice; Oceanography -- Periodicals; 551.4605
• DOI: 10.1029/2018JC014911
• Languages: English
• ISSNs: 2169-9275

Abstract

Abstract: We combine Eulerian ice draft observations from moored ice‐profiling sonars with buoy‐ and satellite‐derived ice drift data to obtain Lagrangian observations of changes in the thickness distribution of sea ice circulating the Beaufort Sea. We examine repeat measurements of ice draft by identifying events where buoys or pseudobuoys made repeat overpasses within 30 km of ice‐profiling sonar‐equipped Beaufort Gyre Exploration Project moorings. Comparison of ice draft distributions from each overpass indicates that summertime melt rates are related to drift track, with more melt occurring in the southern Beaufort Sea than to the north. Additionally, we find that ice surviving summer in the Beaufort Sea since 2007 is similar in thickness to surrounding first‐year sea ice by the end of the following winter. These findings are supported by continuous ice thickness data from ice mass balance buoys. By examining "plumes" of pseudobuoys originating at each mooring location, we identify anomalous northward transport of ice in the southern Beaufort Sea in 2007 that likely contributed to the record‐breaking reduction in sea ice extent that year. We also find that repeat overpasses have been much rarer since 2007, due to reduced summertime sea ice extent in the Beaufort Gyre and possible changes in ice drift patterns. These changes contribute to diminished replenishment of multiyear sea ice volume in the Arctic. Plain Language Summary: Using ice motion data from buoys and satellites, we track sea ice as it circulates in the Beaufort Gyre and measure changes in its thickness as it passes over moored upward looking sonars. Our results show that ice drifting through the southern Beaufort Sea in summer experiences significant thinning and that multiyear ice surviving the summer does not grow much thicker than first‐year ice even after multiple winters. We also find that the northward retreat of the summertime ice edge in Beaufort Sea is leading to a reduced likelihood of ice recirculating and growing older and thicker in the Beaufort Gyre. Together, these changes make any recovery of the Arctic ice pack increasingly unlikely. Key Points: Sea ice in the Beaufort Gyre is tracked as it drifts over upward looking sonars to derive Lagrangian changes in its thickness distribution Sea ice traversing the Beaufort Sea south of ~75°N experiences significantly greater melt since 2007 than ice to the north By the end of winter, perennial ice surviving summer in the Beaufort Gyre is similar in thickness to first‐year ice grown in just one season