Stanton Timothy P.

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Timothy P.

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Now showing 1 - 5 of 5
  • Article
    Evolution of a Canada Basin ice-ocean boundary layer and mixed layer across a developing thermodynamically forced marginal ice zone
    (John Wiley & Sons, 2016-08-22) Gallaher, Shawn G. ; Stanton, Timothy P. ; Shaw, William J. ; Cole, Sylvia T. ; Toole, John M. ; Wilkinson, Jeremy P. ; Maksym, Ted ; Hwang, Byongjun
    A comprehensive set of autonomous, ice-ocean measurements were collected across the Canada Basin to study the summer evolution of the ice-ocean boundary layer (IOBL) and ocean mixed layer (OML). Evaluation of local heat and freshwater balances and associated turbulent forcing reveals that melt ponds (MPs) strongly influence the summer IOBL-OML evolution. Areal expansion of MPs in mid-June start the upper ocean evolution resulting in significant increases to ocean absorbed radiative flux (19 W m−2 in this study). Buoyancy provided by MP drainage shoals and freshens the IOBL resulting in a 39 MJ m−2 increase in heat storage in just 19 days (52% of the summer total). Following MP drainage, a near-surface fresh layer deepens through shear-forced mixing to form the summer mixed layer (sML). In late summer, basal melt increases due to stronger turbulent mixing in the thin sML and the expansion of open water areas due in part to wind-forced divergence of the sea ice. Thermal heterogeneities in the marginal ice zone (MIZ) upper ocean led to large ocean-to-ice heat fluxes (100–200 W m−2) and enhanced basal ice melt (3–6 cm d−1), well away from the ice edge. Calculation of the upper ocean heat budget shows that local radiative heat input accounted for at least 89% of the observed latent heat losses and heat storage (partitioned 0.77/0.23). These results suggest that the extensive area of deteriorating sea ice observed away from the ice edge during the 2014 season, termed the “thermodynamically forced MIZ,” was driven primarily by local shortwave radiative forcing.
  • Article
    Overview of the MOSAiC expedition: physical oceanography
    (University of California Press, 2022-02-07) Rabe, Benjamin ; Heuzé, Céline ; Regnery, Julia ; Aksenov, Yevgeny ; Allerholt, Jacob ; Athanase, Marylou ; Bai, Youcheng ; Basque, Chris R. ; Bauch, Dorothea ; Baumann, Till M. ; Chen, Dake ; Cole, Sylvia T. ; Craw, Lisa ; Davies, Andrew ; Damm, Ellen ; Dethloff, Klaus ; Divine, Dmitry V. ; Doglioni, Francesca ; Ebert, Falk ; Fang, Ying-Chih ; Fer, Ilker ; Fong, Allison A. ; Gradinger, Rolf ; Granskog, Mats A. ; Graupner, Rainer ; Haas, Christian ; He, Hailun ; Hoppmann, Mario ; Janout, Markus A. ; Kadko, David ; Kanzow, Torsten C. ; Karam, Salar ; Kawaguchi, Yusuke ; Koenig, Zoe ; Kong, Bin ; Krishfield, Richard A. ; Krumpen, Thomas ; Kuhlmey, David ; Kuznetsov, Ivan ; Lan, Musheng ; Laukert, Georgi ; Lei, Ruibo ; Li, Tao ; Torres-Valdes, Sinhue ; Lin, Lina ; Lin, Long ; Liu, Hailong ; Liu, Na ; Loose, Brice ; Ma, Xiaobing ; McKay, Rosalie ; Mallet, Maria ; Mallett, Robbie ; Maslowski, Wieslaw ; Mertens, Christian ; Mohrholz, Volker ; Muilwijk, Morven ; Nicolaus, Marcel ; O’Brien, Jeffrey K. ; Perovich, Donald K. ; Ren, Jian ; Rex, Markus ; Ribeiro, Natalia ; Rinke, Annette ; Schaffer, Janin ; Schuffenhauer, Ingo ; Schulz, Kirstin ; Shupe, Matthew ; Shaw, William J. ; Sokolov, Vladimir T. ; Sommerfeld, Anja ; Spreen, Gunnar ; Stanton, Timothy P. ; Stephens, Mark ; Su, Jie ; Sukhikh, Natalia ; Sundfjord, Arild ; Thomisch, Karolin ; Tippenhauer, Sandra ; Toole, John M. ; Vredenborg, Myriel ; Walter, Maren ; Wang, Hangzhou ; Wang, Lei ; Wang, Yuntao ; Wendisch, Manfred ; Zhao, Jinping ; Zhou, Meng ; Zhu, Jialiang
    Arctic Ocean properties and processes are highly relevant to the regional and global coupled climate system, yet still scarcely observed, especially in winter. Team OCEAN conducted a full year of physical oceanography observations as part of the Multidisciplinary drifting Observatory for the Study of the Arctic Climate (MOSAiC), a drift with the Arctic sea ice from October 2019 to September 2020. An international team designed and implemented the program to characterize the Arctic Ocean system in unprecedented detail, from the seafloor to the air-sea ice-ocean interface, from sub-mesoscales to pan-Arctic. The oceanographic measurements were coordinated with the other teams to explore the ocean physics and linkages to the climate and ecosystem. This paper introduces the major components of the physical oceanography program and complements the other team overviews of the MOSAiC observational program. Team OCEAN’s sampling strategy was designed around hydrographic ship-, ice- and autonomous platform-based measurements to improve the understanding of regional circulation and mixing processes. Measurements were carried out both routinely, with a regular schedule, and in response to storms or opening leads. Here we present along-drift time series of hydrographic properties, allowing insights into the seasonal and regional evolution of the water column from winter in the Laptev Sea to early summer in Fram Strait: freshening of the surface, deepening of the mixed layer, increase in temperature and salinity of the Atlantic Water. We also highlight the presence of Canada Basin deep water intrusions and a surface meltwater layer in leads. MOSAiC most likely was the most comprehensive program ever conducted over the ice-covered Arctic Ocean. While data analysis and interpretation are ongoing, the acquired datasets will support a wide range of physical oceanography and multi-disciplinary research. They will provide a significant foundation for assessing and advancing modeling capabilities in the Arctic Ocean.
  • Article
    Surface freshening in the Arctic Ocean's Eurasian Basin : an apparent consequence of recent change in the wind-driven circulation
    (American Geophysical Union, 2011-07-23) Timmermans, Mary-Louise ; Proshutinsky, Andrey ; Krishfield, Richard A. ; Perovich, Donald K. ; Richter-Menge, Jackie A. ; Stanton, Timothy P. ; Toole, John M.
    Data collected by an autonomous ice-based observatory that drifted into the Eurasian Basin between April and November 2010 indicate that the upper ocean was appreciably fresher than in 2007 and 2008. Sea ice and snowmelt over the course of the 2010 drift amounted to an input of less than 0.5 m of liquid freshwater to the ocean (comparable to the freshening by melting estimated for those previous years), while the observed change in upper-ocean salinity over the melt period implies a freshwater gain of about 0.7 m. Results of a wind-driven ocean model corroborate the observations of freshening and suggest that unusually fresh surface waters observed in parts of the Eurasian Basin in 2010 may have been due to the spreading of anomalously fresh water previously residing in the Beaufort Gyre. This flux is likely associated with a 2009 shift in the large-scale atmospheric circulation to a significant reduction in strength of the anticyclonic Beaufort Gyre and the Transpolar Drift Stream.
  • Article
    Ice and ocean velocity in the Arctic marginal ice zone : ice roughness and momentum transfer
    (University of California Press, 2017-09-21) Cole, Sylvia T. ; Toole, John M. ; Lele, Ratnaksha ; Timmermans, Mary-Louise ; Gallaher, Shawn G. ; Stanton, Timothy P. ; Shaw, William J. ; Hwang, Byongjun ; Maksym, Ted ; Wilkinson, Jeremy P. ; Ortiz, Macarena ; Graber, Hans C. ; Rainville, Luc ; Petty, Alek A. ; Farrell, Sinéad L. ; Richter-Menge, Jackie A. ; Haas, Christian
    The interplay between sea ice concentration, sea ice roughness, ocean stratification, and momentum transfer to the ice and ocean is subject to seasonal and decadal variations that are crucial to understanding the present and future air-ice-ocean system in the Arctic. In this study, continuous observations in the Canada Basin from March through December 2014 were used to investigate spatial differences and temporal changes in under-ice roughness and momentum transfer as the ice cover evolved seasonally. Observations of wind, ice, and ocean properties from four clusters of drifting instrument systems were complemented by direct drill-hole measurements and instrumented overhead flights by NASA operation IceBridge in March, as well as satellite remote sensing imagery about the instrument clusters. Spatially, directly estimated ice-ocean drag coefficients varied by a factor of three with rougher ice associated with smaller multi-year ice floe sizes embedded within the first-year-ice/multi-year-ice conglomerate. Temporal differences in the ice-ocean drag coefficient of 20–30% were observed prior to the mixed layer shoaling in summer and were associated with ice concentrations falling below 100%. The ice-ocean drag coefficient parameterization was found to be invalid in September with low ice concentrations and small ice floe sizes. Maximum momentum transfer to the ice occurred for moderate ice concentrations, and transfer to the ocean for the lowest ice concentrations and shallowest stratification. Wind work and ocean work on the ice were the dominant terms in the kinetic energy budget of the ice throughout the melt season, consistent with free drift conditions. Overall, ice topography, ice concentration, and the shallow summer mixed layer all influenced mixed layer currents and the transfer of momentum within the air-ice-ocean system. The observed changes in momentum transfer show that care must be taken to determine appropriate parameterizations of momentum transfer, and imply that the future Arctic system could become increasingly seasonal.
  • Article
    Winter-to-summer transition of Arctic sea ice breakup and floe size distribution in the Beaufort Sea
    (University of California Press, 2017-07-26) Hwang, Byongjun ; Wilkinson, Jeremy P. ; Maksym, Ted ; Graber, Hans C. ; Schweiger, Axel ; Horvat, Christopher ; Perovich, Donald K. ; Arntsen, Alexandra ; Stanton, Timothy P. ; Ren, Jinchang ; Wadhams, Peter
    Breakup of the near-continuous winter sea ice into discrete summer ice floes is an important transition that dictates the evolution and fate of the marginal ice zone (MIZ) of the Arctic Ocean. During the winter of 2014, more than 50 autonomous drifting buoys were deployed in four separate clusters on the sea ice in the Beaufort Sea, as part of the Office of Naval Research MIZ program. These systems measured the ocean-ice-atmosphere properties at their location whilst the sea ice parameters in the surrounding area of these buoy clusters were continuously monitored by satellite TerraSAR-X Synthetic Aperture Radar. This approach provided a unique Lagrangian view of the winter-to-summer transition of sea ice breakup and floe size distribution at each cluster between March and August. The results show the critical timings of a) temporary breakup of winter sea ice coinciding with strong wind events and b) spring breakup (during surface melt, melt ponding and drainage) leading to distinctive summer ice floes. Importantly our results suggest that summer sea ice floe distribution is potentially affected by the state of winter sea ice, including the composition and fracturing (caused by deformation events) of winter sea ice, and that substantial mid-summer breakup of sea ice floes is likely linked to the timing of thermodynamic melt of sea ice in the area. As the rate of deformation and thermodynamic melt of sea ice has been increasing in the MIZ in the Beaufort Sea, our results suggest that these elevated factors would promote faster and more enhanced breakup of sea ice, leading to a higher melt rate of sea ice and thus a more rapid advance of the summer MIZ.