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Wendy Ermold

Physicist IV

Email

wermold@apl.washington.edu

Phone

206-543-7112

Department Affiliation

Polar Science Center

Projects

Seasonality of Circumpolar Tundra: Ocean and Atmosphere Controls and Effects on Energy and Carbon Budgets

Through this project, investigators will characterize the seasonal linkages between the land surface greenness and a suite of land, atmosphere, and ocean characteristics, focusing on the Beringia/ Beaufort Sea, where there have been strong positive increases in the Normalized Difference Vegetation Index (NDVI) over the past 25 years, and the west-central Arctic Eurasia region, where the NDVI trends have been slightly negative. This is a collaborative project led by Howard Epstein at the University of Virginia with Uma Bhatt, Univ. of Alaska, Fairbanks, and Mike Steele, University of Washington.

 

Videos

Polar Science Weekend @ Pacific Science Center

This annual event at the Pacific Science Center shares polar science with thousands of visitors. APL-UW researchers inspire appreciation and interest in polar science through dozens of live demonstrations and hands-on activities.

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10 Mar 2017

Polar research and technology were presented to thousands of visitors by APL-UW staff during the Polar Science Weekend at Seattle's Pacific Science Center. The goal of is to inspire an appreciation and interest in science through one-on-one, face-to-face interactions between visitors and scientists. Guided by their 'polar passports', over 10,000 visitors learned about the Greenland ice sheet, the diving behavior of narwhals, the difference between sea ice and freshwater ice, how Seagliders work, and much more as they visited dozens of live demonstrations and activities.

The Polar Science Weekend has grown from an annual outreach event to an educational research project funded by NASA, and has become a model for similar activities hosted by the Pacific Science Center. A new program trains scientists and volunteers how to interact with the public and how to design engaging exhibits.

Arctic Switchyard

Like a railroad switchyard where loads come together, rearrange, and exit, the water masses of the Arctic Ocean are tracked as they move toward the North Atlantic Ocean.

1 Nov 2010

Publications

2000-present and while at APL-UW

Changing seasonality of panarctic tundra vegetation in relationship to climatic variables

Bhatt, U.S., D.A. Walker, M.I. Raynolds, P.A. Bieniek, H.E. Epstein, J.C. Comiso, J.E. Pinzon, C.J. Tucker, M. Steele, W. Ermold, and J. Zhang, "Changing seasonality of panarctic tundra vegetation in relationship to climatic variables," Environ. Res. Lett., 12, doi:10.1088/1748-9326/aa6b0b, 2017.

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5 May 2017

Potential climate drivers of Arctic tundra vegetation productivity are investigated to understand recent greening and browning trends documented by maximum normalized difference vegetation index (NDVI) (MaxNDVI) and time-integrated NDVI (TI-NDVI) for 1982–2015. Over this period, summer sea ice has continued to decline while oceanic heat content has increased. The increases in summer warmth index (SWI) and NDVI have not been uniform over the satellite record. SWI increased from 1982 to the mid-1990s and remained relatively flat from 1998 onwards until a recent upturn. While MaxNDVI displays positive trends from 1982–2015, TI-NDVI increased from 1982 until 2001 and has declined since. The data for the first and second halves of the record were analyzed and compared spatially for changing trends with a focus on the growing season. Negative trends for MaxNDVI and TI-NDVI were more common during 1999–2015 compared to 1982–1998.

Trend analysis within the growing season reveals that sea ice decline was larger in spring for the 1982–1998 period compared to 1999–2015, while fall sea ice decline was larger in the later period. Land surface temperature trends for the 1982–1998 growing season are positive and for 1999–2015 are positive in May–June but weakly negative in July–August. Spring biweekly NDVI trends are positive and significant for 1982–1998, consistent with increasing open water and increased available warmth in spring. MaxNDVI trends for 1999–2015 display significant negative trends in May and the first half of June.

Numerous possible drivers of early growing season NDVI decline coincident with warming temperatures are discussed, including increased standing water, delayed spring snow-melt, winter thaw events, and early snow melt followed by freezing temperatures. Further research is needed to robustly identify drivers of the spring NDVI decline.

Loitering of the retreating sea ice edge in the Arctic Seas

Steele, M., and W. Ermold, "Loitering of the retreating sea ice edge in the Arctic Seas," J. Geophys. Res., 120, 7699-7721, doi:10.1002/2015JC011182, 2015.

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1 Dec 2015

Each year, the arctic sea ice edge retreats from its winter maximum extent through the Seasonal Ice Zone (SIZ) to its summer minimum extent. On some days, this retreat happens at a rapid pace, while on other days, parts of the pan-arctic ice edge hardly move for periods of days up to 1.5 weeks. We term this stationary behavior "ice edge loitering," and identify areas that are more prone to loitering than others. Generally, about 20–25% of the SIZ area experiences loitering, most often only one time at any one location during the retreat season, but sometimes two or more times. The main mechanism controlling loitering is an interaction between surface winds and warm sea surface temperatures in areas from which the ice has already retreated. When retreat happens early enough to allow atmospheric warming of this open water, winds that force ice floes into this water cause melting. Thus, while individual ice floes are moving, the ice edge as a whole appears to loiter. The time scale of loitering is then naturally tied to the synoptic time scale of wind forcing. Perhaps surprisingly, the area of loitering in the arctic seas has not changed over the past 25 years, even as the SIZ area has grown. This is because rapid ice retreat happens most commonly late in the summer, when atmospheric warming of open water is weak. We speculate that loitering may have profound effects on both physical and biological conditions at the ice edge during the retreat season.

Modeling the formation and fate of the near-surface temperature maximum in the Canadian Basin of the Arctic Ocean

Steele, M., W. Ermold, and J. Zhang, "Modeling the formation and fate of the near-surface temperature maximum in the Canadian Basin of the Arctic Ocean," J. Geophys. Res., 116, doi:10.1029/2010JC006803, 2011.

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12 Nov 2011

A numerical model is used to investigate the time and space extent of the near-surface temperature maximum (NSTM) of the Canadian Basin of the Arctic Ocean over the years 2000%u20132009. The NSTM is formed from local summertime absorption of solar radiation which, in some circumstances, descends through the fall and early winter to form a warm subsurface layer just below the winter mixed layer. We find that winter survival of this layer is confined largely to the Beaufort Gyre of the Canadian Basin, where Ekman convergence and downwelling push the summer warm layer down below the winter mixing depth. In recent years, summer stratification has increased, downwelling has accelerated, and the NSTM has warmed as the sea ice cover in the Beaufort Gyre has thinned. The result is a strengthening NSTM which contained enough heat by the end of winter 2007/2008 to melt about 20 cm of sea ice. Northwest of Alaska the model also simulates a second, deeper temperature maximum layer that forms from advection of saltier summer Pacific water. However, this layer is difficult to adequately resolve and maintain given the model's resolution.

More Publications

Acoustics Air-Sea Interaction & Remote Sensing Center for Environmental & Information Systems Center for Industrial & Medical Ultrasound Electronic & Photonic Systems Ocean Engineering Ocean Physics Polar Science Center
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