Maksym Ted

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  • 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
    A textural approach to improving snow depth estimates in the Weddell Sea
    (MDPI, 2020-05-08) Mei, M. Jeffrey ; Maksym, Ted
    The snow depth on Antarctic sea ice is critical to estimating the sea ice thickness distribution from laser altimetry data, such as from Operation IceBridge or ICESat-2. Snow redistributed by wind collects around areas of deformed ice and forms a wide variety of features on sea ice; the morphology of these features may provide some indication of the mean snow depth. Here, we apply a textural segmentation algorithm to classify and group similar textures to infer the distribution of snow using snow surface freeboard measurements from Operation IceBridge campaigns over the Weddell Sea. We find that texturally-similar regions have similar snow/ice ratios, even when they have different absolute snow depth measurements. This allows for the extrapolation of nadir-looking snow radar data using two-dimensional surface altimetry scans, providing a two-dimensional estimate of the snow depth with ∼22% error. We show that at the floe scale (∼180 m), snow depth can be directly estimated from the snow surface with ∼20% error using deep learning techniques, and that the learned filters are comparable to standard textural analysis techniques. This error drops to ∼14% when averaged over 1.5 km scales. These results suggest that surface morphological information can improve remotely-sensed estimates of snow depth, and hence sea ice thickness, as compared to current methods. Such methods may be useful for reducing uncertainty in Antarctic sea ice thickness estimates from ICESat-2.
  • Article
    Direct inference of first-year sea ice thickness using broadband acoustic backscattering
    (Acoustical Society of America, 2020-02-06) Bassett, Christopher ; Lavery, Andone C. ; Lyons, Anthony P. ; Wilkinson, Jeremy P. ; Maksym, Ted
    Accurate measurements of sea ice thickness are critical to better understand climate change, to provide situational awareness in ice-covered waters, and to reduce risks for communities that rely on sea ice. Nonetheless, remotely measuring the thickness of sea ice is difficult. The only regularly employed technique that accurately measures the full ice thickness involves drilling a hole through the ice. Other presently used methods are either embedded in or through the ice (e.g., ice mass balance buoys) or calculate thickness from indirect measurements (e.g., ice freeboard from altimetry; ice draft using sonars; total snow and ice thickness using electromagnetic techniques). Acoustic techniques, however, may provide an alternative approach to measure the total ice thickness. Here laboratory-grown sea ice thicknesses, estimated by inverting the time delay between echoes from the water-ice and ice-air interfaces, are compared to those measured using ice cores. A time-domain model capturing the dominant scattering mechanisms is developed to explore the viability of broadband acoustic techniques for measuring sea ice thickness, to compare with experimental measurements, and to investigate optimal frequencies for in situ applications. This approach decouples ice thickness estimates from water column properties and does not preclude ice draft measurements using the same data.
  • Article
    Changes in snow distribution and surface topography following a snowstorm on Antarctic sea ice
    (John Wiley & Sons, 2016-11-15) Trujillo, Ernesto ; Leonard, Katherine ; Maksym, Ted ; Lehning, Michael
    Snow distribution over sea ice is an important control on sea ice physical and biological processes. We combine measurements of the atmospheric boundary layer and blowing snow on an Antarctic sea ice floe with terrestrial laser scanning to characterize a typical storm and its influence on the spatial patterns of snow distribution at resolutions of 1–10 cm over an area of 100 m × 100 m. The pre-storm surface exhibits multidirectional elongated snow dunes formed behind aerodynamic obstacles. Newly deposited dunes are elongated parallel to the predominant wind direction during the storm. Snow erosion and deposition occur over 62% and 38% of the area, respectively. Snow deposition volume is more than twice that of erosion (351 m3 versus 158 m3), resulting in a modest increase of 2 ± 1 cm in mean snow depth, indicating a small net mass gain despite large mass relocation. Despite significant local snow depth changes due to deposition and erosion, the statistical distributions of elevation and the two-dimensional correlation functions remain similar to those of the pre-storm surface. Pre-storm and post-storm surfaces also exhibit spectral power law relationships with little change in spectral exponents. These observations suggest that for sea ice floes with mature snow cover features under conditions similar to those observed in this study, spatial statistics and scaling properties of snow surface morphology may be relatively invariant. Such an observation, if confirmed for other ice types and conditions, may be a useful tool for model parameterizations of the subgrid variability of sea ice surfaces.
  • Article
    Delivering sustained, coordinated, and integrated observations of the Southern Ocean for global impact
    (Frontiers Media, 2019-08-08) Newman, Louise ; Heil, Petra ; Trebilco, Rowan ; Katsumata, Katsuro ; Constable, Andrew ; van Wijk, Esmee ; Assmann, Karen ; Beja, Joana ; Bricher, Phillippa ; Coleman, Richard ; Costa, Daniel P. ; Diggs, Stephen ; Farneti, Riccardo ; Fawcett, Sarah E. ; Gille, Sarah T. ; Hendry, Katharine R. ; Henley, Sian ; Hofmann, Eileen E. ; Maksym, Ted ; Mazloff, Matthew R. ; Meijers, Andrew J. S. ; Meredith, Michael M. ; Moreau, Sebastien ; Ozsoy, Burcu ; Robertson, Robin ; Schloss, Irene ; Schofield, Oscar M. E. ; Shi, Jiuxin ; Sikes, Elisabeth L. ; Smith, Inga J. ; Swart, Sebastiaan ; Wahlin, Anna ; Williams, Guy ; Williams, Michael J. M. ; Herraiz-Borreguero, Laura ; Kern, Stefan ; Lieser, Jan ; Massom, Robert A. ; Melbourne-Thomas, Jessica ; Miloslavich, Patricia ; Spreen, Gunnar
    The Southern Ocean is disproportionately important in its effect on the Earth system, impacting climatic, biogeochemical, and ecological systems, which makes recent observed changes to this system cause for global concern. The enhanced understanding and improvements in predictive skill needed for understanding and projecting future states of the Southern Ocean require sustained observations. Over the last decade, the Southern Ocean Observing System (SOOS) has established networks for enhancing regional coordination and research community groups to advance development of observing system capabilities. These networks support delivery of the SOOS 20-year vision, which is to develop a circumpolar system that ensures time series of key variables, and delivers the greatest impact from data to all key end-users. Although the Southern Ocean remains one of the least-observed ocean regions, enhanced international coordination and advances in autonomous platforms have resulted in progress toward sustained observations of this region. Since 2009, the Southern Ocean community has deployed over 5700 observational platforms south of 40°S. Large-scale, multi-year or sustained, multidisciplinary efforts have been supported and are now delivering observations of essential variables at space and time scales that enable assessment of changes being observed in Southern Ocean systems. The improved observational coverage, however, is predominantly for the open ocean, encompasses the summer, consists of primarily physical oceanographic variables, and covers surface to 2000 m. Significant gaps remain in observations of the ice-impacted ocean, the sea ice, depths >2000 m, the air-ocean-ice interface, biogeochemical and biological variables, and for seasons other than summer. Addressing these data gaps in a sustained way requires parallel advances in coordination networks, cyberinfrastructure and data management tools, observational platform and sensor technology, two-way platform interrogation and data-transmission technologies, modeling frameworks, intercalibration experiments, and development of internationally agreed sampling standards and requirements of key variables. This paper presents a community statement on the major scientific and observational progress of the last decade, and importantly, an assessment of key priorities for the coming decade, toward achieving the SOOS vision and delivering essential data to all end-users.
  • Article
    Overview of the Arctic Sea state and boundary layer physics program
    (American Geophysical Union, 2018-04-16) Thomson, Jim ; Ackley, Stephen ; Girard-Ardhuin, Fanny ; Ardhuin, Fabrice ; Babanin, Alexander ; Boutin, Guillaume ; Brozena, John ; Cheng, Sukun ; Collins, Clarence ; Doble, Martin ; Fairall, Christopher W. ; Guest, Peter ; Gebhardt, Claus ; Gemmrich, Johannes ; Graber, Hans C. ; Holt, Benjamin ; Lehner, Susanne ; Lund, Björn ; Meylan, Michael ; Maksym, Ted ; Montiel, Fabien ; Perrie, Will ; Persson, Ola ; Rainville, Luc ; Rogers, W. Erick ; Shen, Hui ; Shen, Hayley ; Squire, Vernon ; Stammerjohn, Sharon E. ; Stopa, Justin ; Smith, Madison M. ; Sutherland, Peter ; Wadhams, Peter
    A large collaborative program has studied the coupled air‐ice‐ocean‐wave processes occurring in the Arctic during the autumn ice advance. The program included a field campaign in the western Arctic during the autumn of 2015, with in situ data collection and both aerial and satellite remote sensing. Many of the analyses have focused on using and improving forecast models. Summarizing and synthesizing the results from a series of separate papers, the overall view is of an Arctic shifting to a more seasonal system. The dramatic increase in open water extent and duration in the autumn means that large surface waves and significant surface heat fluxes are now common. When refreezing finally does occur, it is a highly variable process in space and time. Wind and wave events drive episodic advances and retreats of the ice edge, with associated variations in sea ice formation types (e.g., pancakes, nilas). This variability becomes imprinted on the winter ice cover, which in turn affects the melt season the following year.
  • Article
    Emerging trends in the sea state of the Beaufort and Chukchi seas
    (Elsevier, 2016-07-06) Thomson, James M. ; Fan, Yalin ; Stammerjohn, Sharon E. ; Stopa, Justin ; Rogers, W. Erick ; Girard-Ardhuin, Fanny ; Ardhuin, Fabrice ; Shen, Hayley ; Perrie, Will ; Shen, Hui ; Ackley, Stephen ; Babanin, Alexander ; Liu, Qingxiang ; Guest, Peter ; Maksym, Ted ; Wadhams, Peter ; Fairall, Christopher W. ; Persson, Ola ; Doble, Martin J. ; Graber, Hans C. ; Lund, Bjoern ; Squire, Vernon ; Gemmrich, Johannes ; Lehner, Susanne ; Holt, Benjamin ; Meylan, Michael ; Brozena, John ; Bidlot, Jean-Raymond
    The sea state of the Beaufort and Chukchi seas is controlled by the wind forcing and the amount of ice-free water available to generate surface waves. Clear trends in the annual duration of the open water season and in the extent of the seasonal sea ice minimum suggest that the sea state should be increasing, independent of changes in the wind forcing. Wave model hindcasts from four selected years spanning recent conditions are consistent with this expectation. In particular, larger waves are more common in years with less summer sea ice and/or a longer open water season, and peak wave periods are generally longer. The increase in wave energy may affect both the coastal zones and the remaining summer ice pack, as well as delay the autumn ice-edge advance. However, trends in the amount of wave energy impinging on the ice-edge are inconclusive, and the associated processes, especially in the autumn period of new ice formation, have yet to be well-described by in situ observations. There is an implicit trend and evidence for increasing wave energy along the coast of northern Alaska, and this coastal signal is corroborated by satellite altimeter estimates of wave energy.
  • Dataset
    Observations of turbulence and the geometry and circulation of windrows in a small bay in the St. Lawrence Estuary
    ( 2019-11-07) Zippel, Seth F. ; Maksym, Ted ; Scully, Malcolm E. ; Sutherland, Peter ; Dumont, Dany
    Measurements of ocean turbulence, waves, and the geometry and circulation of windrows were made over 5 days in early March in a small bay in the St. Lawrence Estuary. Measurements were made from a small zodiac and from a SWIFT drifter. Two acoustic doppler velocity profilers (ADCPs) were used from the zodiac to measure water velocity and turbulent kinetic energy (TKE) dissipation rates near the surface. The acoustic backscatter from the ADCPs was used in conjunction with a GPS to map the location and spacing of wind aligned rows of bubbles. The SWIFT drifter provided measurements of waves, wind stress, and secondary measurements of TKE dissipation rates. Imagery of the surface was taken with a GoPro camera mounted on the zodiac, and with a DJI MavicPro quadcopter.
  • Article
    Detection and quantification of oil under sea ice : the view from below
    (Elsevier, 2014-08-21) Wilkinson, Jeremy P. ; Boyd, Tim ; Hagen, Bernard ; Maksym, Ted ; Pegau, Scott ; Roman, Christopher N. ; Singh, Hanumant ; Zabilansky, Leonard
    Traditional measures for detecting oil spills in the open-ocean are both difficult to apply and less effective in ice-covered seas. In view of the increasing levels of commercial activity in the Arctic, there is a growing gap between the potential need to respond to an oil spill in Arctic ice-covered waters and the capability to do so. In particular, there is no robust operational capability to remotely locate oil spilt under or encapsulated within sea ice. To date, most research approaches the problem from on or above the sea ice, and thus they suffer from the need to ‘see’ through the ice and overlying snow. Here we present results from a large-scale tank experiment which demonstrate the detection of oil beneath sea ice, and the quantification of the oil layer thickness is achievable through the combined use of an upward-looking camera and sonar deployed in the water column below a covering of sea ice. This approach using acoustic and visible measurements from below is simple and effective, and potentially transformative with respect to the operational response to oil spills in the Arctic marine environment. These results open up a new direction of research into oil detection in ice-covered seas, as well as describing a new and important role for underwater vehicles as platforms for oil-detecting sensors under Arctic sea ice.
  • Article
    Estimating early-winter Antarctic sea ice thickness from deformed ice morphology
    (European Geosciences Union, 2019-11-08) Mei, M. Jeffrey ; Maksym, Ted ; Weissling, Blake ; Singh, Hanumant
    Satellites have documented variability in sea ice areal extent for decades, but there are significant challenges in obtaining analogous measurements for sea ice thickness data in the Antarctic, primarily due to difficulties in estimating snow cover on sea ice. Sea ice thickness (SIT) can be estimated from snow freeboard measurements, such as those from airborne/satellite lidar, by assuming some snow depth distribution or empirically fitting with limited data from drilled transects from various field studies. Current estimates for large-scale Antarctic SIT have errors as high as ∼50 %, and simple statistical models of small-scale mean thickness have similarly high errors. Averaging measurements over hundreds of meters can improve the model fits to existing data, though these results do not necessarily generalize to other floes. At present, we do not have algorithms that accurately estimate SIT at high resolutions. We use a convolutional neural network with laser altimetry profiles of sea ice surfaces at 0.2 m resolution to show that it is possible to estimate SIT at 20 m resolution with better accuracy and generalization than current methods (mean relative errors ∼15 %). Moreover, the neural network does not require specification of snow depth or density, which increases its potential applications to other lidar datasets. The learned features appear to correspond to basic morphological features, and these features appear to be common to other floes with the same climatology. This suggests that there is a relationship between the surface morphology and the ice thickness. The model has a mean relative error of 20 % when applied to a new floe from the region and season. This method may be extended to lower-resolution, larger-footprint data such as such as Operation IceBridge, and it suggests a possible avenue to reduce errors in satellite estimates of Antarctic SIT from ICESat-2 over current methods, especially at smaller scales.
  • Article
    Stable Isotope clues to the formation and evolution of refrozen melt ponds on Arctic Sea ice.
    (American Geophysical Union, 2018-11-15) Tian, Lijun ; Gao, Yongli ; Ackley, Stephen ; Stammerjohn, Sharon E. ; Maksym, Ted ; Weissling, Blake
    Sea ice is one of the determining parameters of the climate system. The presence of melt ponds on the surface of Arctic sea ice plays a critical role in the mass balance of sea ice. A total of nine cores was collected from multiyear ice refrozen melt ponds and adjacent hummocks during the 2015 Arctic Sea State research cruise. The depth profiles of water isotopes, salinity, and ice texture for these sea ice cores were examined to provide information about the development of refrozen melt ponds and water balance generation processes, which are otherwise difficult to acquire. The presence of meteoric water with low oxygen isotope values as relatively thin layers indicates melt pond water stability and little mixing during formation and refreezing. The hydrochemical characteristics of refrozen melt pond and seawater depth profiles indicate little snowmelt enters the upper ocean during melt pond refreezing. Due to the seasonal characters of deuterium excess for Arctic precipitation, water balance calculations utilizing two isotopic tracers (oxygen isotope and deuterium excess) suggest that besides the melt of snow cover, the precipitation input in the melt season may also play a role in the evolution of melt ponds. The dual‐isotope mixing model developed here may become more valuable in a future scenario of increasing Arctic precipitation. The layers of meteoric origin were found at different depths in the refrozen melt pond ice cores. Surface topography information collected at several core sites was examined for possible explanations of different structures of refrozen melt ponds.
  • Article
    Broadband acoustic backscatter from crude oil under laboratory-grown sea ice
    (Acoustical Society of America, 2016-10-04) Bassett, Christopher ; Lavery, Andone C. ; Maksym, Ted
    In ice-covered seas, traditional air-side oil spill detection methods face practical challenges. Conversely, under-ice remote sensing techniques are increasingly viable due to improving operational capabilities of autonomous and remotely operated vehicles. To investigate the potential for under-ice detection of oil spills using active acoustics, laboratory measurements of high-frequency, broadband backscatter (75–590 kHz) from crude oil layers (0.7–8.1 cm) under and encapsulated within sea ice were performed at normal and 20 incidence angles. Discrete interfaces (water-oil, oil-ice, and ice-oil) are identifiable in observations following oil injections under the ice and during the subsequent encapsulation. A one-dimensional model for the total normal incidence backscatter from oil under ice, constrained by oil sound speed measurements from 10 C to 20 C and improved environmental measurements compared to previous studies, agrees well with preencapsulation observations. At 20 incidence angles echoes from the ice and oil under ice are more complex and spatially variable than normal incidence observations, most likely due to interface roughness and volume inhomogeneities. Encapsulated oil layers are only detected at normal incidence. The results suggest that high-frequency, broadband backscatter techniques may allow under-ice remote sensing for the detection and quantification of oil spills.
  • Article
    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.
  • Article
    A new structure for the Sea Ice Essential Climate variables of the Global Climate Observing System
    (American Meteorological Society, 2022-06-01) Lavergne, Thomas ; Kern, Stefan ; Aaboe, Signe ; Derby, Lauren ; Dybkjaer, Gorm ; Garric, Gilles ; Heil, Petra ; Hendricks, Stefan ; Holfort, Jürgen ; Howell, Stephen ; Key, Jeffrey ; Lieser, Jan ; Maksym, Ted ; Maslowski, Wieslaw ; Meier, Walt ; Muñoz-Sabater, Joaquín ; Nicolas, Julien ; Ozsoy, Burcu ; Rabe, Benjamin ; Rack, Wolfgang ; Raphael, Marilyn ; de Rosnay, Patricia ; Smolyanitsky, Vasily ; Tietsche, Steffen ; Ukita, Jinro ; Vichi, Marcello ; Wagner, Penelope M. ; Willmes, Sascha ; Zhao, Xi
    Climate observations inform about the past and present state of the climate system. They underpin climate science, feed into policies for adaptation and mitigation, and increase awareness of the impacts of climate change. The Global Climate Observing System (GCOS), a body of the World Meteorological Organization (WMO), assesses the maturity of the required observing system and gives guidance for its development. The Essential Climate Variables (ECVs) are central to GCOS, and the global community must monitor them with the highest standards in the form of Climate Data Records (CDR). Today, a single ECV—the sea ice ECV—encapsulates all aspects of the sea ice environment. In the early 1990s it was a single variable (sea ice concentration) but is today an umbrella for four variables (adding thickness, edge/extent, and drift). In this contribution, we argue that GCOS should from now on consider a set of seven ECVs (sea ice concentration, thickness, snow depth, surface temperature, surface albedo, age, and drift). These seven ECVs are critical and cost effective to monitor with existing satellite Earth observation capability. We advise against placing these new variables under the umbrella of the single sea ice ECV. To start a set of distinct ECVs is indeed critical to avoid adding to the suboptimal situation we experience today and to reconcile the sea ice variables with the practice in other ECV domains.
  • Article
    Antarctic sea ice—A polar opposite?
    (The Oceanography Society, 2012-09) Maksym, Ted ; Stammerjohn, Sharon E. ; Ackley, Stephen ; Massom, Robert A.
    As the world's ice diminishes in the face of climate change—from the dramatic decline in Arctic sea ice, to thinning at the margins of both the Greenland and Antarctic ice sheets, to retreating mountain glaciers the world over—Antarctic sea ice presents something of a paradox. The trend in total sea ice extent in the Antarctic has remained steady, or even increased slightly, over the past three decades, confounding climate model predictions showing moderate to strong declines. This apparent intransigence masks dramatic regional trends; declines in sea ice in the Bellingshausen Sea region that rival the high-profile decline in the Arctic have been matched by opposing increases in the Ross Sea. Much of the explanation lies in the unique nature of the Antarctic sea ice zone. Its position surrounding the continent and exposure to the high-energy wind and wave fields of the open Southern Ocean shape both its properties and its connection to the atmosphere and ocean in ways very different from the Arctic. Sea ice extent and variability are strongly driven by large-scale climate variability patterns such as the El Niño-Southern Oscillation and the Southern Annular Mode. Because many of these patterns have opposing effects in different regions around the continent, decreases in one region are often accompanied by similar, opposing increases in another. Yet, the failure of climate models to capture either the overall or regional behavior also reflects, in part, a poor understanding of sea ice processes. Considerable insight has been gained into the nature of these processes over the past several decades through field expeditions aboard icebreakers. However, much remains to be discovered about the nature of Antarctic sea ice; its connections with the ocean, atmosphere, and ecosystem; and its complex response to present and future climate change.
  • Article
    Supercooled Southern Ocean waters
    (American Geophysical Union, 2020-10-09) Haumann, F. Alexander ; Moorman, Ruth ; Riser, Stephen C. ; Smedsrud, Lars H. ; Maksym, Ted ; Wong, Annie P. S. ; Wilson, Earle A. ; Drucker, Robert S. ; Talley, Lynne D. ; Johnson, Kenneth S. ; Key, Robert M. ; Sarmiento, Jorge L.
    In cold polar waters, temperatures sometimes drop below the freezing point, a process referred to as supercooling. However, observational challenges in polar regions limit our understanding of the spatial and temporal extent of this phenomenon. We here provide observational evidence that supercooled waters are much more widespread in the seasonally ice‐covered Southern Ocean than previously reported. In 5.8% of all analyzed hydrographic profiles south of 55°S, we find temperatures below the surface freezing point (“potential” supercooling), and half of these have temperatures below the local freezing point (“in situ” supercooling). Their occurrence doubles when neglecting measurement uncertainties. We attribute deep coastal‐ocean supercooling to melting of Antarctic ice shelves and surface‐induced supercooling in the seasonal sea‐ice region to wintertime sea‐ice formation. The latter supercooling type can extend down to the permanent pycnocline due to convective sinking plumes—an important mechanism for vertical tracer transport and water‐mass structure in the polar ocean.
  • Article
    Physical and biological properties of early winter Antarctic sea ice in the Ross Sea.
    (Cambridge University Press, 2020-06-24) Tison, Jean-Louis ; Maksym, Ted ; Fraser, Alexander D. ; Corkill, Matthew ; Kimura, Noriaki ; Nosaka, Yuichi ; Nomura, Daiki ; Vancoppenolle, Martin ; Ackley, Stephen ; Stammerjohn, Sharon E. ; Wauthy, Sarah ; Van der Linden, Fanny ; Carnat, Gauthier ; Sapart, Célia ; de Jong, Jeroen ; Fripiat, Francois ; Delille, Bruno
    This work presents the results of physical and biological investigations at 27 biogeochemical stations of early winter sea ice in the Ross Sea during the 2017 PIPERS cruise. Only two similar cruises occurred in the past, in 1995 and 1998. The year 2017 was a specific year, in that ice growth in the Central Ross Sea was considerably delayed, compared to previous years. These conditions resulted in lower ice thicknesses and Chl-a burdens, as compared to those observed during the previous cruises. It also resulted in a different structure of the sympagic algal community, unusually dominated by Phaeocystis rather than diatoms. Compared to autumn-winter sea ice in the Weddell Sea (AWECS cruise), the 2017 Ross Sea pack ice displayed similar thickness distribution, but much lower snow cover and therefore nearly no flooding conditions. It is shown that contrasted dynamics of autumnal-winter sea-ice growth between the Weddell Sea and the Ross Sea impacted the development of the sympagic community. Mean/median ice Chl-a concentrations were 3–5 times lower at PIPERS, and the community status there appeared to be more mature (decaying?), based on Phaeopigments/Chl-a ratios. These contrasts are discussed in the light of temporal and spatial differences between the two cruises.
  • Article
    Counting whales in a challenging, changing environment
    (Nature Publishing Group, 2014-03-13) Williams, R. ; Kelly, N. ; Boebel, Olaf ; Friedlaender, Ari S. ; Herr, H. ; Kock, K.-H. ; Lehnert, L. S. ; Maksym, Ted ; Roberts, Jason J. ; Scheidat, M. ; Siebert, U. ; Brierley, A. S.
    Estimating abundance of Antarctic minke whales is central to the International Whaling Commission's conservation and management work and understanding impacts of climate change on polar marine ecosystems. Detecting abundance trends is problematic, in part because minke whales are frequently sighted within Antarctic sea ice where navigational safety concerns prevent ships from surveying. Using icebreaker-supported helicopters, we conducted aerial surveys across a gradient of ice conditions to estimate minke whale density in the Weddell Sea. The surveys revealed substantial numbers of whales inside the sea ice. The Antarctic summer sea ice is undergoing rapid regional change in annual extent, distribution, and length of ice-covered season. These trends, along with substantial interannual variability in ice conditions, affect the proportion of whales available to be counted by traditional shipboard surveys. The strong association between whales and the dynamic, changing sea ice requires reexamination of the power to detect trends in whale abundance or predict ecosystem responses to climate change.
  • 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
    Laboratory measurements of high-frequency, acoustic broadband backscattering from sea ice and crude oil
    (Acoustical Society of America, 2014-12-18) Bassett, Christopher ; Lavery, Andone C. ; Maksym, Ted ; Wilkinson, Jeremy P.
    Recent decreases in summer sea ice cover are spurring interest in hydrocarbon extraction and shipping in Arctic waters, increasing the risk of an oil spill in ice covered waters. With advances in unmanned vehicle operation, there is an interest in identifying techniques for remote, underwater detection of oil spills from below. High-frequency (200–565 kHz), broadband acoustic scattering data demonstrate that oil can be detected and quantified under laboratory grown sea ice and may be of use in natural settings. A simple scattering model based on the reflection coefficients from the interfaces agrees well with the data.