Perovich Donald K.

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Perovich

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Donald K.

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Influences of the ocean surface mixed layer and thermohaline stratification on Arctic Sea ice in the central Canada Basin

(American Geophysical Union, 2010-10-08) Toole, John M. ; Timmermans, Mary-Louise ; Perovich, Donald K. ; Krishfield, Richard A. ; Proshutinsky, Andrey ; Richter-Menge, Jackie A.

Variations in the Arctic central Canada Basin mixed layer properties are documented based on a subset of nearly 6500 temperature and salinity profiles acquired by Ice-Tethered Profilers during the period summer 2004 to summer 2009 and analyzed in conjunction with sea ice observations from ice mass balance buoys and atmosphere-ocean heat flux estimates. The July–August mean mixed layer depth based on the Ice-Tethered Profiler data averaged 16 m (an overestimate due to the Ice-Tethered Profiler sampling characteristics and present analysis procedures), while the average winter mixed layer depth was only 24 m, with individual observations rarely exceeding 40 m. Guidance interpreting the observations is provided by a 1-D ocean mixed layer model. The analysis focuses attention on the very strong density stratification at the base of the mixed layer in the Canada Basin that greatly impedes surface layer deepening and thus limits the flux of deep ocean heat to the surface that could influence sea ice growth/decay. The observations additionally suggest that efficient lateral mixed layer restratification processes are active in the Arctic, also impeding mixed layer deepening.
Arctic Ocean warming contributes to reduced polar ice cap

(American Meteorological Society, 2010-12) Polyakov, Igor V. ; Timokhov, Leonid A. ; Alexeev, Vladimir A. ; Bacon, Sheldon ; Dmitrenko, Igor A. ; Fortier, Louis ; Frolov, Ivan E. ; Gascard, Jean-Claude ; Hansen, Edmond ; Ivanov, Vladimir V. ; Laxon, Seymour W. ; Mauritzen, Cecilie ; Perovich, Donald K. ; Shimada, Koji ; Simmons, Harper L. ; Sokolov, Vladimir T. ; Steele, Michael ; Toole, John M.

Analysis of modern and historical observations demonstrates that the temperature of the intermediate-depth (150–900 m) Atlantic water (AW) of the Arctic Ocean has increased in recent decades. The AW warming has been uneven in time; a local 1°C maximum was observed in the mid-1990s, followed by an intervening minimum and an additional warming that culminated in 2007 with temperatures higher than in the 1990s by 0.24°C. Relative to climatology from all data prior to 1999, the most extreme 2007 temperature anomalies of up to 1°C and higher were observed in the Eurasian and Makarov Basins. The AW warming was associated with a substantial (up to 75–90 m) shoaling of the upper AW boundary in the central Arctic Ocean and weakening of the Eurasian Basin upper-ocean stratification. Taken together, these observations suggest that the changes in the Eurasian Basin facilitated greater upward transfer of AW heat to the ocean surface layer. Available limited observations and results from a 1D ocean column model support this surmised upward spread of AW heat through the Eurasian Basin halocline. Experiments with a 3D coupled ice–ocean model in turn suggest a loss of 28–35 cm of ice thickness after 50 yr in response to the 0.5 W m−2 increase in AW ocean heat flux suggested by the 1D model. This amount of thinning is comparable to the 29 cm of ice thickness loss due to local atmospheric thermodynamic forcing estimated from observations of fast-ice thickness decline. The implication is that AW warming helped precondition the polar ice cap for the extreme ice loss observed in recent years.
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.
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.
Surface flooding of Antarctic summer sea ice

(Cambridge University Press, 2020-06-11) Ackley, Stephen ; Perovich, Donald K. ; Maksym, Ted ; Weissling, Blake ; Xie, Hongjie

The surface flooding of Antarctic sea ice in summer covers 50% or more of the sea-ice area in the major summer ice packs, the western Weddell and the Bellingshausen-Amundsen Seas. Two CRREL ice mass-balance buoys were deployed on the Amundsen Sea pack in late December 2010 from the icebreaker Oden, bridging the summer period (January–February 2011). Temperature records from thermistors embedded vertically in the snow and ice showed progressive increases in the depth of the flooded layer (up to 0.3–0.35 m) on the ice cover during January and February. While the snow depth was relatively unchanged from accumulation (<10 cm), ice thickness decreased by up to a meter from bottom melting during this period. Contemporaneous with the high bottom melting, under-ice water temperatures up to 1°C above the freezing point were found. The high temperature arises from solar heating of the upper mixed layer which can occur when ice concentration in the local area falls and lower albedo ocean water is exposed to radiative heating. The higher proportion of snow ice found in the Amundsen Sea pack ice therefore results from both winter snowfall and summer ice bottom melt found here that can lead to extensive surface flooding.
Toward quantifying the increasing role oceanic heat in sea ice loss in the new Arctic

(American Meteorological Society, 2015-12) Carmack, Eddy C. ; Polyakov, Igor V. ; Padman, Laurie ; Fer, Ilker ; Hunke, Elizabeth C. ; Hutchings, Jennifer K. ; Jackson, Jennifer M. ; Kelley, Daniel E. ; Kwok, Ron ; Layton, Chantelle ; Melling, Humfrey ; Perovich, Donald K. ; Persson, Ola ; Ruddick, Barry R. ; Timmermans, Mary-Louise ; Toole, John M. ; Ross, Tetjana ; Vavrus, Steve ; Winsor, Peter

The loss of Arctic sea ice has emerged as a leading signal of global warming. This, together with acknowledged impacts on other components of the Earth system, has led to the term “the new Arctic.” Global coupled climate models predict that ice loss will continue through the twenty-first century, with implications for governance, economics, security, and global weather. A wide range in model projections reflects the complex, highly coupled interactions between the polar atmosphere, ocean, and cryosphere, including teleconnections to lower latitudes. This paper summarizes our present understanding of how heat reaches the ice base from the original sources—inflows of Atlantic and Pacific Water, river discharge, and summer sensible heat and shortwave radiative fluxes at the ocean/ice surface—and speculates on how such processes may change in the new Arctic. The complexity of the coupled Arctic system, and the logistic and technological challenges of working in the Arctic Ocean, require a coordinated interdisciplinary and international program that will not only improve understanding of this critical component of global climate but will also provide opportunities to develop human resources with the skills required to tackle related problems in complex climate systems. We propose a research strategy with components that include 1) improved mapping of the upper- and middepth Arctic Ocean, 2) enhanced quantification of important process, 3) expanded long-term monitoring at key heat-flux locations, and 4) development of numerical capabilities that focus on parameterization of heat-flux mechanisms and their interactions.
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.
Influence of ice thickness and surface properties on light transmission through Arctic sea ice

(John Wiley & Sons, 2015-09-04) Katlein, Christian ; Arndt, Stefanie ; Nicolaus, Marcel ; Perovich, Donald K. ; Jakuba, Michael V. ; Suman, Stefano ; Elliott, Stephen M. ; Whitcomb, Louis L. ; McFarland, Christopher J. ; Gerdes, Rudiger ; Boetius, Antje ; German, Christopher R.

The observed changes in physical properties of sea ice such as decreased thickness and increased melt pond cover severely impact the energy budget of Arctic sea ice. Increased light transmission leads to increased deposition of solar energy in the upper ocean and thus plays a crucial role for amount and timing of sea-ice-melt and under-ice primary production. Recent developments in underwater technology provide new opportunities to study light transmission below the largely inaccessible underside of sea ice. We measured spectral under-ice radiance and irradiance using the new Nereid Under-Ice (NUI) underwater robotic vehicle, during a cruise of the R/V Polarstern to 83°N 6°W in the Arctic Ocean in July 2014. NUI is a next generation hybrid remotely operated vehicle (H-ROV) designed for both remotely piloted and autonomous surveys underneath land-fast and moving sea ice. Here we present results from one of the first comprehensive scientific dives of NUI employing its interdisciplinary sensor suite. We combine under-ice optical measurements with three dimensional under-ice topography (multibeam sonar) and aerial images of the surface conditions. We investigate the influence of spatially varying ice-thickness and surface properties on the spatial variability of light transmittance during summer. Our results show that surface properties such as melt ponds dominate the spatial distribution of the under-ice light field on small scales (<1000 m2), while sea ice-thickness is the most important predictor for light transmission on larger scales. In addition, we propose the use of an algorithm to obtain histograms of light transmission from distributions of sea ice thickness and surface albedo.
Spatial and temporal variability of oceanic heat flux to the Arctic ice pack

(American Geophysical Union, 2005-07-27) Krishfield, Richard A. ; Perovich, Donald K.

In order to simulate the large-scale structure and temporal variability of oceanic heat flux (F w) to the Arctic perennial ice pack, observations of heat in the mixed layer and ice dynamics are compared with parameterizations and climatologies. Long-term drifting platform observations of seawater temperature and salinity (primarily from automated buoys) are used to describe the annual cycle of temperature above freezing (ΔT f) in the mixed layer beneath the ice pack, which are modulated by ice-ocean friction velocities (u*) determined from the platform drifts to produce estimates of F w between 1975 and 1998. On average, ΔT f is not negligible in winter, especially in the Transpolar Drift, which implies a positive F w to the ice pack by means other than solar heating. A parameterization based solely on the solar zenith angle (with a 1 month lag) is found to largely describe the observed ΔT f (with root mean square error of 0.03°C), despite the lack of an albedo or open water term. A reconstruction of F w from 1979 to 2002 is produced by modulating parameterized ΔT f with u* on the basis of daily ice drift estimates from a composite satellite and in situ data set. The reconstructed estimates are corrected for regional variations and are compared to independent estimates of F w from ice mass balance measurements, indicating annual F w averages between 3 and 4 W m−2 depending on the selection of under-ice roughness length in the ice-ocean stress calculations. Although the interannual variations in ΔT f are fixed by the parameterization in the derived reconstruction, the dynamics indicate an overall positive trend (0.2 W m−2 decade−1) in Arctic F w, with the largest variations found in the southern Beaufort Gyre.
Introduction to the special issue on the new Artic Ocean

(Oceanography Society, 2022-12-08) Weingartner, Thomas ; Ashjian, Carin ; Brigham, Lawson ; Haine, Thomas ; Mack, Liza ; Perovich, Don ; Rabe, Benjamin

One hundred and thirty years ago, Fridtjof Nansen, the Norwegian polar explorer and scientist, set off on a bold three-year journey to investigate the unknown Arctic Ocean. The expedition relied on a critical technological development: a small, strong, and maneuverable vessel, powered by sail and an engine, with an endurance of five years for twelve men. His intellectual curiosity and careful observations led to an early glimpse of the Arctic Ocean’s circulation and its unique ecosystem. Some of Nansen’s findings on sea ice and the penetration of Atlantic Water into the Arctic Ocean established a benchmark against which we have measured profound changes over the past few decades. In contrast, little was known about the Arctic Ocean’s ecosystem processes prior to the onset of anthropogenic climate change. Nansen’s successes, which paved the way for subsequent research, were gained in part from Indigenous Greenlanders who taught him how to survive in this harsh environment.

Perovich Donald K.

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