Strong and highly variable push of ocean waves on Southern Ocean sea ice

Sea ice in the Southern Ocean has expanded over most of the past 20 y, but the decline in sea ice since 2016 has taken experts by surprise. This recent evolution highlights the poor performance of numerical models for predicting extent and thickness, which is due to our poor understanding of ice dynamics. Ocean waves are known to play an important role in ice break-up and formation. In addition, as ocean waves decay, they cause a stress that pushes the ice in the direction of wave propagation. This wave stress could not previously be quantified due to insufficient observations at large scales. Sentinel-1 synthetic aperture radars (SARs) provide high-resolution imagery from which wave height is measured year round encompassing Antarctica since 2014. Our estimates give an average wave stress that is comparable to the average wind stress acting over 50 km of sea ice. We further reveal highly variable half-decay distances ranging from 400 m to 700 km, and wave stresses from 0.01 to 1 Pa. We expect that this variability is related to ice properties and possibly different floe sizes and ice thicknesses. A strong feedback of waves on sea ice, via break-up and rafting, may be the cause of highly variable sea-ice properties.

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Seasonal Food Web Dynamics in the Antarctic Benthos of Tethys Bay (Ross Sea): Implications for Biodiversity Persistence Under Different Seasonal Sea-Ice Coverage

Frontiers in Marine Science ◽

10.3389/fmars.2020.594454 ◽

2020 ◽

Vol 7 ◽

Author(s):

Simona Sporta Caputi ◽

Giulio Careddu ◽

Edoardo Calizza ◽

Federico Fiorentino ◽

Deborah Maccapan ◽

...

Keyword(s):

Sea Ice ◽

Food Web ◽

Ross Sea ◽

Food Web Structure ◽

Ice Dynamics ◽

Web Architecture ◽

Sea Ice Dynamics ◽

Before And After ◽

Basal Resources ◽

Break Up

Determining food web architecture and its seasonal cycles is a precondition for making predictions about Antarctic marine biodiversity under varying climate change scenarios. However, few scientific data concerning Antarctic food web structure, the species playing key roles in web stability and the community responses to changes in sea-ice dynamics are available. Based on C and N stable isotope analysis, we describe Antarctic benthic food webs and the diet of species occurring in shallow waters (Tethys Bay, Ross Sea) before and after seasonal sea-ice break-up. We hypothesized that the increased availability of primary producers (sympagic algae) following sea-ice break-up affects the diet of species and thus food web architecture. Basal resources had distinct isotopic signatures that did not change after sea-ice break-up, enabling a robust description of consumer diets based on Bayesian mixing models. Sympagic algae had the highest δ13C (∼−14‰) and red macroalgae the lowest (∼−37‰). Consumer isotopic niches and signatures changed after sea-ice break-up, reflecting the values of sympagic algae. Differences in food web topology were also observed. The number of taxa and the number of links per taxon were higher before the thaw than after it. After sea-ice break-up, sympagic inputs allowed consumers to specialize on abundant resources at lower trophic levels. Foraging optimization by consumers led to a simpler food web, with lower potential competition and shorter food chains. However, basal resources and Antarctic species such as the bivalve Adamussium colbecki and the sea-urchin Sterechinus neumayeri were central and highly connected both before and after the sea-ice break-up, thus playing key roles in interconnecting species and compartments in the web. Any disturbance affecting these species is expected to have cascading effects on the entire food web. The seasonal break-up of sea ice in Antarctica ensures the availability of resources that are limiting for coastal communities for the rest of the year. Identification of species playing a key role in regulating food web structure in relation to seasonal sea-ice dynamics, which are expected to change with global warming, is central to understanding how these communities will respond to climate change.

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Timing and magnitude of Southern Ocean sea ice/carbon cycle feedbacks

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1908670117 ◽

2020 ◽

Vol 117 (9) ◽

pp. 4498-4504 ◽

Cited By ~ 4

Author(s):

Karl Stein ◽

Axel Timmermann ◽

Eun Young Kwon ◽

Tobias Friedrich

Keyword(s):

Carbon Cycle ◽

Southern Ocean ◽

Sea Ice ◽

General Circulation ◽

Deep Ocean ◽

General Circulation Models ◽

Ice Dynamics ◽

Carbon Cycle Model ◽

Ocean Stratification ◽

Ocean Ventilation

The Southern Ocean (SO) played a prominent role in the exchange of carbon between ocean and atmosphere on glacial timescales through its regulation of deep ocean ventilation. Previous studies indicated that SO sea ice could dynamically link several processes of carbon sequestration, but these studies relied on models with simplified ocean and sea ice dynamics or snapshot simulations with general circulation models. Here, we use a transient run of an intermediate complexity climate model, covering the past eight glacial cycles, to investigate the orbital-scale dynamics of deep ocean ventilation changes due to SO sea ice. Cold climates increase sea ice cover, sea ice export, and Antarctic Bottom Water formation, which are accompanied by increased SO upwelling, stronger poleward export of Circumpolar Deep Water, and a reduction of the atmospheric exposure time of surface waters by a factor of 10. Moreover, increased brine formation around Antarctica enhances deep ocean stratification, which could act to decrease vertical mixing by a factor of four compared with the current climate. Sensitivity tests with a steady-state carbon cycle model indicate that the two mechanisms combined can reduce atmospheric carbon by 40 ppm, with ocean stratification acting early within a glacial cycle to amplify the carbon cycle response.

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Overview of the MOSAiC expedition – Snow and Sea Ice

10.5194/egusphere-egu21-10136 ◽

2021 ◽

Author(s):

Marcel Nicolaus ◽

Donald Perovich ◽

Keyword(s):

Sea Ice ◽

Multiple Scales ◽

Numerical Models ◽

Spatial Scales ◽

Coupled System ◽

Ice Dynamics ◽

Different Seasons ◽

Remote Sensing Methods ◽

Ice Pack ◽

Snow And Ice

Year-round observations of the properties and processes that govern the ice pack and its interaction with the atmosphere and the ocean were the key element of the MOSAiC field experiment. The aim was to completely characterize the properties of the snow and ice cover across different spatial scales over an entire annual cycle. This was done by monitoring snow and ice mass balance, observing the evolving energy budget, studying dynamical features, and by documenting snow and ice dynamics over nested spatial scales. We conducted in-situ observations at multiple scales, which will be integrated in numerical models and remote sensing methods. Overall, we performed the most comprehensive snow and sea ice program to date. Here, we summarize the observational snow and sea ice program during the drift from October 2019 to September 2020. We will present improved concepts and diagnostics of the field program and show relationships to satellite retrievals and numerical models. We will highlight individual events and characteristics of the snow and ice pack during the different seasons based on time-series that were obtained from numerous sea-ice programs of the MOSAiC ICE team. We will discuss the various activities with respect to the coupled system and the life cycle of sea ice along the transpolar drift.

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Timing and magnitude of Southern Ocean sea ice/carbon cycle feedbacks over the last eight glacial cycles

10.5194/egusphere-egu2020-1755 ◽

2020 ◽

Author(s):

Karl Stein ◽

Axel Timmermann ◽

Eun Young Kwon ◽

Tobias Friedrich

Keyword(s):

Carbon Sequestration ◽

Carbon Cycle ◽

Southern Ocean ◽

Sea Ice ◽

Deep Ocean ◽

Glacial Cycles ◽

Ice Dynamics ◽

Ocean Stratification ◽

Ocean Ventilation ◽

The Impact

The Southern Ocean (SO) played a prominent role in the exchange of carbon between ocean and atmosphere on glacial timescales through its regulation of deep ocean ventilation. Previous studies indicated that SO sea ice could dynamically link several processes of carbon sequestration, but these studies relied on models with simplified ocean and sea ice dynamics or snapshot simulations with general circulation models. Here we use a transient run of the LOVECLIM intermediate complexity climate model, covering the past eight glacial cycles, to investigate the orbital-scale dynamics of deep ocean ventilation changes due to SO sea ice. Cold climates increase sea ice cover, sea-ice export, and Antarctic Bottom Water formation, which are accompanied by increased SO upwelling, stronger poleward export of Circumpolar Deep Water, and a reduction of the atmospheric exposure time of surface waters by a factor of ten. Moreover, increased brine formation around Antarctica enhances deep ocean stratification, which could act to decrease vertical mixing by a factor of four compared to the current climate. The impact of the two mechanisms on carbon sequestration was then tested within a steady-state carbon cycle. The two mechanisms combined can reduce atmospheric carbon by 40 ppm, of which approximately 30 ppm is due to ocean stratification. Moreover, ocean stratification from increased SO sea ice production acts early within glacial cycles to amplify the carbon cycle response.

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Spatial distribution of the iron supply to phytoplankton in the Southern Ocean: a model study

Biogeosciences ◽

10.5194/bg-6-2861-2009 ◽

2009 ◽

Vol 6 (12) ◽

pp. 2861-2878 ◽

Cited By ~ 90

Author(s):

C. Lancelot ◽

A. de Montety ◽

H. Goosse ◽

S. Becquevort ◽

V. Schoemann ◽

...

Keyword(s):

Spatial Distribution ◽

Southern Ocean ◽

Sea Ice ◽

Atmospheric Deposition ◽

Weddell Sea ◽

Ice Dynamics ◽

Iron Storage ◽

Chl A ◽

Iron Supply ◽

Iceberg Calving

Abstract. An upgraded version of the biogeochemical model SWAMCO is coupled to the ocean-sea-ice model NEMO-LIM to explore processes governing the spatial distribution of the iron supply to phytoplankton in the Southern Ocean. The 3-D NEMO-LIM-SWAMCO model is implemented in the ocean domain south of latitude 30° S and runs are performed over September 1989–December 2000. Model scenarios include potential iron sources (atmospheric deposition, iceberg calving/melting and continental sediments) as well as iron storage within sea ice, all formulated based on a literature review. When all these processes are included, the simulated iron profiles and phytoplankton bloom distributions show satisfactory agreement with observations. Analyses of simulations and sensitivity tests point to the key role played by continental sediments as a primary source for iron. Iceberg calving and melting contribute by up to 25% of Chl-a simulated in areas influenced by icebergs while atmospheric deposition has little effect at high latitudes. Activating sea ice-ocean iron exchanges redistribute iron geographically. Stored in the ice during winter formation, iron is then transported due to ice motion and is released and made available to phytoplankton during summer melt, in the vicinity of the marginal ice zones. Transient iron storage and transport associated with sea ice dynamics stimulate summer phytoplankton blooming (up to 3 mg Chl-a m-3 in the Weddell Sea and off East Antarctica but not in the Ross, Bellingshausen and Amundsen Seas. This contrasted feature results from the simulated variable content of iron in sea ice and release of melting ice showing higher ice-ocean iron fluxes in the continental shelves of the Weddell and Ross Seas than in the Eastern Weddell Sea and the Bellingshausen-Amundsen Seas. This study confirms that iron sources and transport in the Southern Ocean likely provide important mechanisms in the geographical development of phytoplankton blooms and associated ecosystems.

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On a Simple Sea-Ice Dynamics Model for Climate Studies

Annals of Glaciology ◽

10.3189/s0260305500008296 ◽

1990 ◽

Vol 14 ◽

pp. 72-77 ◽

Cited By ~ 7

Author(s):

G.M. Flato ◽

W.D. Hibler

Keyword(s):

Sea Ice ◽

Large Scale ◽

Wind Fields ◽

Fluid Approximation ◽

Ice Dynamics ◽

Monthly Average ◽

Sea Ice Dynamics ◽

Average Wind ◽

Cavitating Fluid ◽

Climate Studies

Sea-ice motion and dynamic thickness build-up play an important role in the transfer of heat between the ocean and the atmosphere and so must be included in large-scale climate studies. A “cavitating-fluid” approximation allows these dynamic processes to be parameterized in a simple way by ignoring shear and tensile strength yet retaining compressive strength. A simple procedure for approximating a cavitating fluid is presented here and is compared to the more complete viscous-plastic sea-ice model by performing several three year simulations with daily varying and monthly average wind forcing. Although differences exist on a monthly basis, the two models compare favourably over a seasonal cycle, particularly when compared to a thermodynamics only model in which ice motion is ignored. The lack of shear strength in a cavitating-fluid approximation makes it less sensitive to smoothing of the wind fields (as demonstrated by the monthly average wind simulations); however it also changes the detailed circulation and thickness build-up patterns somewhat. Overall, the cavitating-fluid approximation shows considerable promise for including sea-ice dynamics in large-scale climate models, especially where averaged wind fields are employed.

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Winter sea ice export from the Laptev Sea preconditions the local summer sea ice cover and fast ice decay

The Cryosphere ◽

10.5194/tc-11-2383-2017 ◽

2017 ◽

Vol 11 (5) ◽

pp. 2383-2391 ◽

Cited By ~ 12

Author(s):

Polona Itkin ◽

Thomas Krumpen

Keyword(s):

Sea Ice ◽

Numerical Models ◽

Ice Cover ◽

Sensitivity Study ◽

Arctic Sea Ice ◽

Late Winter ◽

Laptev Sea ◽

Ice Dynamics ◽

Fast Ice ◽

The Laptev Sea

Abstract. Ice retreat in the eastern Eurasian Arctic is a consequence of atmospheric and oceanic processes and regional feedback mechanisms acting on the ice cover, both in winter and summer. A correct representation of these processes in numerical models is important, since it will improve predictions of sea ice anomalies along the Northeast Passage and beyond. In this study, we highlight the importance of winter ice dynamics for local summer sea ice anomalies in thickness, volume and extent. By means of airborne sea ice thickness surveys made over pack ice areas in the south-eastern Laptev Sea, we show that years of offshore-directed sea ice transport have a thinning effect on the late-winter sea ice cover. To confirm the preconditioning effect of enhanced offshore advection in late winter on the summer sea ice cover, we perform a sensitivity study using a numerical model. Results verify that the preconditioning effect plays a bigger role for the regional ice extent. Furthermore, they indicate an increase in volume export from the Laptev Sea as a consequence of enhanced offshore advection, which has far-reaching consequences for the entire Arctic sea ice mass balance. Moreover we show that ice dynamics in winter not only preconditions local summer ice extent, but also accelerate fast-ice decay.

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A new coupled model to shed light on sea-ice--ocean interactions

10.5194/egusphere-egu21-10122 ◽

2021 ◽

Author(s):

Guillaume Boutin ◽

Einar Ólason ◽

Pierre Rampal ◽

Camille Lique ◽

Claude Talandier ◽

...

Keyword(s):

Sea Ice ◽

Numerical Models ◽

Coupled Model ◽

Small Scale ◽

Polar Regions ◽

Fine Scale ◽

Ice Dynamics ◽

Damage Propagation ◽

Sea Ice Dynamics ◽

The Impact

Sea ice is a key component of the earth&#8217;s climate system as it modulates air-sea interactions in polar regions. These interactions strongly depend on openings in the sea ice cover, which are associated with fine-scale sea ice deformations. Visco-plastic sea ice rheologies used in most numerical models struggle at representing these fine-scale sea ice dynamics without going to very costly horizontal resolutions (~1km). A solution is to use damage propagation sea ice models, which were shown to reproduce well sea ice deformations with little dependency on the mesh resolution.&#160;Here we present results from the first ocean--sea-ice coupled model using a rheology with damage propagation. The ocean component is the NEMO-OPA model. The sea ice component is neXtSIM, introducing the newly developed Brittle Bingham-Maxwell rheology. Results show that sea ice dynamics are very well represented from large scales (sea ice drift) to small-scales (sea ice deformation). Sea ice properties relevant for climate, i.e volume and area, also show a remarkable match with satellite observations. This coupled framework opens new opportunities to quantify the impact of small-scale sea ice dynamics on ice-ocean interactions.

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Landfast ice in the Canadian Sub-Arctic: A Hudson-Bay wide study.

10.5194/egusphere-egu2020-12232 ◽

2020 ◽

Author(s):

Kaushik Gupta ◽

Anirban Mukhopadhyay ◽

Jens Ehn

Keyword(s):

Sea Ice ◽

Ice Formation ◽

Hudson Bay ◽

James Bay ◽

Stages Of Development ◽

Ice Dynamics ◽

Landfast Ice ◽

Coastal Margin ◽

Break Up ◽

North Western

Hudson Bay, along with James Bay, forms a significant section of the Canadian Sub-Arctic basin which experiences an annual event of Land-fast sea ice formation and melt. Here Landfast ice dynamics largely depends on the climatic and oceanographic conditions, along with coastal geomorphology. In this study, we attempt to investigate the annual cycle of land-fast sea ice formation and melt in the Hudson Bay and James Bay region by estimating the ice period, stages of development and extent. Through this study, we also emphasize the role of coastal morphology influencing ice stability. We have analysed over 2000 ice charts produced by the Canadian Ice Service (CIS) and satellite observations from Worldview and LANDSAT series. The Canadian Ice Service publishes charts of ice concentration and stages of development of Hudson Bay and James Bay on a monthly, weekly and daily scale. We observe the variation in land-fast ice dynamics by digitally extracting information from the daily and weekly ice charts produced by the CIS and satellite observation coupled with mean surface temperature throughout the period of study. Our results indicate landfast ice forming earlier and breaking later in the northern and north-western coastal margin of Hudson Bay as compared to the southern and eastern shore. James Bay experiences a relatively shorter ice season than Hudson Bay. Though time series analysis of break-up in the northern and north-western Hudson Bay shows a negative trend implying an earlier break-up in these regions. Southern and eastern Hudson Bay and James Bay have a positive trend implying a negligible change in the break-up period. The extent of landfast ice in the eastern coastal margins of Hudson Bay and James Bay was noted to be significantly more compared to the west, primarily due to the north to south and finally eastward movement of pack ice in the bay system. Complex coastal topography in the eastern coastal margin also contributes to the stability of these extended ice sheets. The study determines the description of the multiyear variability of land-fast sea ice under changing temperature regimes over the Canadian Sub-Arctic.

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Local climatology of fast ice in McMurdo Sound, Antarctica

Antarctic Science ◽

10.1017/s0954102017000578 ◽

2018 ◽

Vol 30 (2) ◽

pp. 125-142 ◽

Cited By ~ 16

Author(s):

Stacy Kim ◽

Ben Saenz ◽

Jeff Scanniello ◽

Kendra Daly ◽

David Ainley

Keyword(s):

Sea Ice ◽

Ross Sea ◽

Wind Waves ◽

Marine Ecosystem ◽

Sea Ice Concentration ◽

Ice Dynamics ◽

Mcmurdo Sound ◽

High Resolution Imagery ◽

Pack Ice ◽

Fast Ice

AbstractFast ice plays important physical and ecological roles: as a barrier to wind, waves and radiation, as both barrier and safe resting place for air-breathing animals, and as substrate for microbial communities. While sea ice has been monitored for decades using satellite imagery, high-resolution imagery sufficient to distinguish fast ice from mobile pack ice extends only back to c. 2000. Fast ice trends may differ from previously identified changes in regional sea ice distributions. To investigate effects of climate and human activities on fast ice dynamics in McMurdo Sound, Ross Sea, the sea and fast ice seasonal events (1978–2015), ice thicknesses and temperatures (1986–2014), wind velocities (1973–2015) and dates that an icebreaker annually opens a channel to McMurdo Station (1956–2015) are reported. A significant relationship exists between sea ice concentration and fast ice extent in the Sound. While fast/sea ice retreat dates have not changed, fast/sea ice reaches a minimum later and begins to advance earlier, in partial agreement with changes in Ross Sea regional pack ice dynamics. Fast ice minimum extent within McMurdo Sound is significantly correlated with icebreaker arrival date as well as wind velocity. The potential impacts of changes in fast ice climatology on the local marine ecosystem are discussed.

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