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Yanling Yu

Senior Oceanographer--Retiree

Email

yanling@apl.washington.edu

Phone

206-543-1254

Biosketch

Dr. Yu investigates arctic sea ice and its role in arctic climate and ocean circulation. Analyzing submarine observations, she and her colleagues examine the long-term changes in mean ice thickness and its distribution. She also uses dynamic and thermodynamic models and statistic methods to search for clues as to why some changes have occurred and how these changes can be characterized in both space and time.

She has developed an algorithm to derive arctic thin ice thickness by combining a thermodynamic sea ice model with the satellite observations from Advanced Very High Resolution Radiometer (AVHRR) imagery. This algorithm can be used to study the aggregated sea ice properties dependent on thin ice thickness distribution, such as brine flux from growing young ice and large-scale ice strength. Dr. Yu and her colleagues have begun to investigate the interannual variability of arctic landfast ice and its contribution to the freshwater budget on the arctic shelves.

Department Affiliation

Polar Science Center

Education

B.S. Meteorology, Ocean University of Quingdao, China, 1982

M.S. Physical Oceanography, University of Washington, 1990

Ph.D. Physical Oceanography, University of Washington, 1996

Publications

2000-present and while at APL-UW

Responses of surface heat flux, sea ice and ocean dynamics in the Chukchi–Beaufort sea to storm passages during winter 2006/2007: A numerical study

Bai, X., H. Hu, J. Wang, Y. Yu, E. Cassano, and J. Maslanik, "Responses of surface heat flux, sea ice and ocean dynamics in the Chukchi–Beaufort sea to storm passages during winter 2006/2007: A numerical study," Deep Sea Res. I, 102, 101-117, doi:10.1016/j.dsr.2015.04.008, 2015.

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1 Aug 2015

This study investigates storm impacts on sea ice, oceanic dynamics, and surface heat flux in the Chukchi–Beaufort Seas using a coupled ice–ocean model (CIOM). Two types of storms affect the study area: Arctic-born cyclones and north-moving Aleutian lows, which lead to strong westerly and easterly winds, respectively. Driven by 6-hourly forcing, the CIOM successfully reproduced the storm impacts. Simulated sea ice movements are comparable to the satellite observations. Storms usually result in fast-moving ice, which is faster than the speed of the surface water, and the gap between sea ice and surface water speed increases with wind speed. Storms can alter the pathways of the Pacific inflow water: with westerly winds, the Pacific inflow water goes no further than the latitude of Wrangel Island, while with easterly winds the Pacific inflow water can flow northward into the interior Arctic basin. Strong easterly winds associated with north-moving Aleutian lows reverse the Alaskan Coastal Current and the Bering Slope Current, and induce upwelling along the north Alaska coast. Westerly winds associated with Arctic-born cyclones act in an opposite way. During the storms, heat loss to the atmosphere is about twice that of normal conditions, which is mainly attributed to increases of the sensible and latent heat fluxes over the open water. Heat loss over ice was quite stable with some small fluctuations in response to the storms.

The Mackenzie Estuary of the Arctic Ocean

Macdonald , R.W., and Y. Yu, "The Mackenzie Estuary of the Arctic Ocean," Handbook Environ. Chem., 91-120, doi:10.1007/698_5_027, 2005.

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7 Oct 2005

The Mackenzie Estuary is a seasonally ice covered, deltaic estuary. It receives over 300 km3 of freshwater and 125 x 106 t of sediment annually in a strongly modulated seasonal cycle. Ice cover plays a crucial role in the physical setting by limiting air--sea interaction (energy and gas exchange), reducing mixing, and withdrawing freshwater from the estuary while leaving behind the bulk of the dissolved components. Few studies have been conducted on estuarine processes occurring in this estuary and, although we can project from temperate estuaries what the important conservative and nonconservative processes are likely to be, the winter encroachment by ice sufficiently alters the physical, chemical, and biological processes that projections from other estuaries will likely be wrong.

Here we discuss how the estuary evolves through the seasonal cycles of temperature, ice cover, river inflow, particle loadings, and winds, and review what is known of the biogeochemical cycling within the estuary. Given that the Arctic is exceptionally vulnerable to change, especially in the marginal seas, it is safe to predict that remote, pristine estuaries of the Arctic are as much at risk in the future as estuaries more directly impacted by human encroachment.

Changes in the thickness distribution of Arctic sea ice between 1958-1970 and 1993-1997

Yu, Y., G.A. Maykut, and D.A. Rothrock, "Changes in the thickness distribution of Arctic sea ice between 1958-1970 and 1993-1997," J. Geophys. Res., 109, 10.1029/2003JC001982, 2004.

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6 Aug 2004

Submarine sonar data collected in the central Arctic Basin during middle and late summer were used to examine differences in the sea ice thickness distribution function g(h) between the periods 1958–1970 and 1993–1997. Cruises during the former period were made in July and August, whereas the 1993–1997 cruises were made in September and October. Seasonal correction was applied to adjust for the differences in thickness. While ice drafts were from only seven submarine cruises and somewhat spatially limited, results indicate that the fractional area covered by open water and first-year ice increased from 0.19 to 0.30 during the time interval. This was balanced by an 11% reduction of level-multiyear and ridged ice. Substantial losses occurred in ice thicker than 2 m, with an increase in the amount of 1–2 m ice. The volume of ice less than 4 m thick remained nearly the same and the total volume decreased about 32%. Losses in the volume of thicker ice increased with increasing thickness. Part of the change in g(h) is likely caused by increased ice area export through Fram Strait in the late 1980s and early 1990s. Because decadal variations in the North Atlantic Oscillation and Arctic Oscillation indices correlate with ice export anomalies, export-induced changes in g(h) probably tend to be cyclical in nature. However, a substantial shift in the peak of g(h) suggests that changes in thermal forcing were also a major factor in the observed thinning.

More Publications

Comparison of thin ice thickness distributions derived from RADARSAT Geophysical Processor System and advanced very high resolution radiometer data sets

Yu, Y., and R.W. Lindsay, "Comparison of thin ice thickness distributions derived from RADARSAT Geophysical Processor System and advanced very high resolution radiometer data sets," J. Geophys. Res., 108, 10.1029/2001JC000805, 2003.

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26 Dec 2003

Thin ice thickness distributions estimated from advanced very high resolution radiometer (AVHRR) and RADARSAT Geophysical Processor System (RGPS) data sets were compared over the Beaufort Sea and the Canada Basin for the period December 1996 to February 1997. The comparisons show a compelling agreement. High correlations were found in cases where thin ice grew in large, wide leads extending several hundred kilometers. At these large scales, estimates from AVHRR images and RGPS showed similar amounts of thin ice in leads. However, when major surface deformation occurred on small scales (100 m to 10 km), the finer spatial resolution (100 m) of RADARSAT images enabled the RGPS algorithm to derive more thin ice than that of AVHRR. Under such conditions the correlation between the two dropped, and a small negative bias (about 1%) was observed in the estimates from AVHRR. This bias, mostly concentrated at the very thin end of the thickness distribution, caused a further deficit in the AVHRR-derived thin ice growth, roughly 0.2 cm/d. Although the AVHRR and RGPS algorithms treat snowfall differently in the ice thickness calculations, both snow assumptions appear reasonable. However, RGPS may underestimate the thin ice production because of the 3-day sampling interval. With a better understanding of the sources of uncertainty and improved satellite estimates, a combination of these two satellite data could offer a wider coverage of thin ice thickness observations in the Arctic Basin.

Assimilation of ice motion observations and comparisons with submarine ice thickness data

Zhang, J., D.R. Thomas, D.A. Rothrock, R.W. Lindsay, Y. Yu, and R. Kwok, "Assimilation of ice motion observations and comparisons with submarine ice thickness data," J. Geophys. Res., 108, 10.1029/2001JC001041, 2003.

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3 Jun 2003

Aided by submarine observations of ice thickness for model evaluation, we investigate the effects of assimilating buoy motion data and satellite SSM/I (85 Ghz) ice motion data on simulation of Arctic sea ice. The sea-ice model is a thickness and enthalpy distribution model and is coupled to an ocean model. Ice motion data are assimilated by means of optimal interpolation. Assimilating motion data, particularly from drifting buoys, significantly improves the modeled ice motion, reducing the error to 0.04 m s-1 from 0.07 m s-1 and increasing the correlation with observations to 0.90 from 0.66. Without data assimilation, the modeled ice moves too slowly with excessive stoppage. Assimilation leads to more robust ice motion with substantially reduced stoppage, which in turn leads to strengthened ice outflow at Fram Strait and enhanced ice deformation everywhere. Enhanced deformation doubles the production of ridged ice to an Arctic Ocean average of 0.77 m yr-1, and raises the amount of ridged ice to half the total ice volume per unit area of 2.58 m. Assimilation also significantly alters the spatial distribution of ice mass and brings the modeled ice thickness into better agreement with the thickness observed in four recent submarine cruises, reducing the error to 0.66 m from 0.76 m, and increasing the correlation with observations to 0.65 from 0.45. Buoy data are most effective in reducing model errors because of their small measurement error. SSM/I data, because of their more complete spatial coverage, are helpful in regions with few buoys, particularly in coastal areas. Assimilating both SSM/I and buoy data combines their individual advantages and brings about the best overall model performance in simulating both ice motion and ice thickness.

The arctic ice thickness anomaly of the 1990s: A consistent view from observations and models

Rothrock, D.A., J. Zhang, and Y. Yu, "The arctic ice thickness anomaly of the 1990s: A consistent view from observations and models," J. Geophys. Res., 108, 10.1029/2001JC001208, 2003.

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18 Mar 2003

Observations of sea-ice draft from submarine cruises in much of the Arctic Ocean show that the ice cover was unusually thin in the mid-1990s. Here we limit our examination to digitally recorded draft data from eight cruises spanning the years 1987 to 1997 and find a decrease of about 1 m over the 11-year span. Comparisons of our modeled draft with observed draft show good agreement in the temporal change. Comparing average draft over entire cruises, the RMS discrepancy between modeled and observed draft is 0.3 m and the correlation is 0.98. Agreement in the spatial patterns of draft is somewhat lower; the RMS discrepancy of 50-km averages of draft is 0.7 m and the correlation is 0.73. We review reports of interannual variations of ice thickness or volume from other model studies. All models agree that thickness decreased by between 0.6 and 0.9 m from 1987 to 1996. Our model shows a modest recovery in thickness from 1996 to 1999. For the 1950s, 1960s, and 1970s, models tend to disagree on the size and to a lesser extent the timing or phase of interannual variations.

Thin ice impacts on surface salt flux and ice strength: Inferences from advanced very high resolution radiometer

Yu, Y., D.A. Rothrock, and J. Zhang, "Thin ice impacts on surface salt flux and ice strength: Inferences from advanced very high resolution radiometer," J. Geophys. Res., 106, 13,975-13,988, doi:10.1029/2000JC000311, 2001.

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15 Jul 2001

Temperatures and albedos derived from satellite imagery are combined with a thermodynamic ice model to estimate thin ice thickness distributions over the Beaufort and the northern Greenland seas. The study shows that thin ice (thinner than 1 m) occupied over half the area in the seasonal ice zones in November and December of 1990 but dropped significantly in April 1991; the Beaufort Shelf showed the largest seasonal change. The aggregate properties of surface salt flux and compressive ice strength, both strongly dependent on the thin end of the ice thickness distribution, were estimated with data from advanced very high resolution radiometer to reveal the spatial and temporal variations over a large scale. The salt flux from growing thin ice was 1–2 orders of magnitude larger on the Beaufort and Greenland Shelves than in the deep basins. On the shelves, flux from thin ice accounted for over 90% of the total surface salt budget. These satellite-derived estimates provided detailed spatial information on salt flux, which can be of great use in studies of surface patterns of salinity forcing and shelf-basin interaction. Also revealed by the satellite data was the wide range in values of compressive strength, which affects how freely the ice cover can deform. Strengths were low in early winter and in seasonal ice zones and nearly doubled in spring. Both thin ice fraction and compressive ice strength estimated from satellite imagery were in good agreement with those simulated by a coupled ice-ocean model.

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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