Understanding Melting due to Ocean Eddy Heat Fluxes at the Edge of Sea-Ice Floes

Abstract The study analyzes the sensitivity and memory of the Southern Hemisphere coupled climate system to increased Antarctic sea ice (ASI), taking into account the persistence of the sea ice maxima in the current climate. The mechanisms involved in restoring the climate balance under two sets of experiments, which differ in regard to their sea ice models, are discussed. The experiments are perturbed with extremes of ASI and integrated for 10 yr in a large 30-member ensemble. The results show that an ASI maximum is able to persist for ~4 yr in the current climate, followed by a negative sea ice phase. The sea ice insulating effect during the positive phase reduces heat fluxes south of 60°S, while at the same time these are intensified at the sea ice edge. The increased air stability over the sea ice field strengthens the polar cell while the baroclinicity increases at midlatitudes. The mean sea level pressure is reduced (increased) over high latitudes (midlatitudes), typical of the southern annular mode (SAM) positive phase. The Southern Ocean (SO) becomes colder and fresher as the sea ice melts mainly through sea ice lateral melting, the consequence of which is an increase in the ocean stability by buoyancy and mixing changes. The climate sensitivity is triggered by the sea ice insulating process and the resulting freshwater pulse (fast response), while the climate equilibrium is restored by the heat stored in the SO subsurface layers (long response). It is concluded that the time needed for the ASI anomaly to be dissipated and/or melted is shortened by the sea ice dynamical processes.

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Sea ice led to poleward-shifted winds at the Last Glacial Maximum: the influence of state dependency on CMIP5 and PMIP3 models

Climate of the Past ◽

10.5194/cp-12-2241-2016 ◽

2016 ◽

Vol 12 (12) ◽

pp. 2241-2253 ◽

Cited By ~ 23

Author(s):

Louise C. Sime ◽

Dominic Hodgson ◽

Thomas J. Bracegirdle ◽

Claire Allen ◽

Bianca Perren ◽

...

Keyword(s):

Sea Ice ◽

Last Glacial Maximum ◽

Heat Fluxes ◽

Glacial Maximum ◽

State Dependency ◽

Last Glacial ◽

Poleward Shift ◽

Future Warming ◽

Ice Edge ◽

Sea Ice Edge

Abstract. Latitudinal shifts in the Southern Ocean westerly wind jet could drive changes in the glacial to interglacial ocean CO2 inventory. However, whilst CMIP5 model results feature consistent future-warming jet shifts, there is considerable disagreement in deglacial-warming jet shifts. We find here that the dependence of pre-industrial (PI) to Last Glacial Maximum (LGM) jet shifts on PI jet position, or state dependency, explains less of the shifts in jet simulated by the models for the LGM compared with future-warming scenarios. State dependence is also weaker for intensity changes, compared to latitudinal shifts in the jet. Winter sea ice was considerably more extensive during the LGM. Changes in surface heat fluxes, due to this sea ice change, probably had a large impact on the jet. Models that both simulate realistically large expansions in sea ice and feature PI jets which are south of 50° S show an increase in wind speed around 55° S and can show a poleward shift in the jet between the PI and the LGM. However, models with the PI jet positioned equatorwards of around 47° S do not show this response: the sea ice edge is too far from the jet for it to respond. In models with accurately positioned PI jets, a +1° difference in the latitude of the sea ice edge tends to be associated with a −0.85° shift in the 850 hPa jet. However, it seems that around 5° of expansion of LGM sea ice is necessary to hold the jet in its PI position. Since the Gersonde et al. (2005) data support an expansion of more than 5°, this result suggests that a slight poleward shift and intensification was the most likely jet change between the PI and the LGM. Without the effect of sea ice, models simulate poleward-shifted westerlies in warming climates and equatorward-shifted westerlies in colder climates. However, the feedback of sea ice counters and reverses the equatorward trend in cooler climates so that the LGM winds were more likely to have also been shifted slightly poleward.

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Airborne observations and simulations of three-dimensional radiative interactions between Arctic boundary layer clouds and ice floes

Atmospheric Chemistry and Physics ◽

10.5194/acp-15-8147-2015 ◽

2015 ◽

Vol 15 (14) ◽

pp. 8147-8163 ◽

Cited By ~ 12

Author(s):

M. Schäfer ◽

E. Bierwirth ◽

A. Ehrlich ◽

E. Jäkel ◽

M. Wendisch

Keyword(s):

Boundary Layer ◽

Radiative Transfer ◽

Sea Ice ◽

Three Dimensional ◽

Open Water ◽

Radiative Effects ◽

Arctic Boundary Layer ◽

Boundary Layer Clouds ◽

Ice Edge ◽

Ice Floes

Abstract. Based on airborne spectral imaging observations, three-dimensional (3-D) radiative effects between Arctic boundary layer clouds and highly variable Arctic surfaces were identified and quantified. A method is presented to discriminate between sea ice and open water under cloudy conditions based on airborne nadir reflectivity γλ measurements in the visible spectral range. In cloudy cases the transition of γλ from open water to sea ice is not instantaneous but horizontally smoothed. In general, clouds reduce γλ above bright surfaces in the vicinity of open water, while γλ above open sea is enhanced. With the help of observations and 3-D radiative transfer simulations, this effect was quantified to range between 0 and 2200 m distance to the sea ice edge (for a dark-ocean albedo of αwater = 0.042 and a sea-ice albedo of αice = 0.91 at 645 nm wavelength). The affected distance Δ L was found to depend on both cloud and sea ice properties. For a low-level cloud at 0–200 m altitude, as observed during the Arctic field campaign VERtical Distribution of Ice in Arctic clouds (VERDI) in 2012, an increase in the cloud optical thickness τ from 1 to 10 leads to a decrease in Δ L from 600 to 250 m. An increase in the cloud base altitude or cloud geometrical thickness results in an increase in Δ L; for τ = 1/10 Δ L = 2200 m/1250 m in case of a cloud at 500–1000 m altitude. To quantify the effect for different shapes and sizes of ice floes, radiative transfer simulations were performed with various albedo fields (infinitely long straight ice edge, circular ice floes, squares, realistic ice floe field). The simulations show that Δ L increases with increasing radius of the ice floe and reaches maximum values for ice floes with radii larger than 6 km (500–1000 m cloud altitude), which matches the results found for an infinitely long, straight ice edge. Furthermore, the influence of these 3-D radiative effects on the retrieved cloud optical properties was investigated. The enhanced brightness of a dark pixel next to an ice edge results in uncertainties of up to 90 and 30 % in retrievals of τ and effective radius reff, respectively. With the help of Δ L, an estimate of the distance to the ice edge is given, where the retrieval uncertainties due to 3-D radiative effects are negligible.

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An analytical model for wind-driven Arctic summer sea ice drift

The Cryosphere ◽

10.5194/tc-10-227-2016 ◽

2016 ◽

Vol 10 (1) ◽

pp. 227-244 ◽

Cited By ~ 11

Author(s):

H.-S. Park ◽

A. L. Stewart

Keyword(s):

Sea Ice ◽

Analytical Model ◽

Surface Wind ◽

Open Water ◽

Sea Ice Concentration ◽

Efficient Calculation ◽

Sea Ice Drift ◽

Wind Input ◽

Ice Floes ◽

Arctic Summer

Abstract. The authors present an analytical model for wind-driven free drift of sea ice that allows for an arbitrary mixture of ice and open water. The model includes an ice–ocean boundary layer with an Ekman spiral, forced by transfers of wind-input momentum both through the sea ice and directly into the open water between the ice floes. The analytical tractability of this model allows efficient calculation of the ice velocity provided that the surface wind field is known and that the ocean geostrophic velocity is relatively weak. The model predicts that variations in the ice thickness or concentration should substantially modify the rotation of the velocity between the 10 m winds, the sea ice, and the ocean. Compared to recent observational data from the first ice-tethered profiler with a velocity sensor (ITP-V), the model is able to capture the dependencies of the ice speed and the wind/ice/ocean turning angles on the wind speed. The model is used to derive responses to intensified southerlies on Arctic summer sea ice concentration, and the results are shown to compare closely with satellite observations.

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Snow-ice growth: a fresh-water flux inhibiting deep convection in the Weddell Sea, Antarctica

Annals of Glaciology ◽

10.3189/172756401781818752 ◽

2001 ◽

Vol 33 ◽

pp. 45-50 ◽

Cited By ~ 14

Author(s):

V.I. Lytle ◽

S.F. Ackley

Keyword(s):

Sea Ice ◽

Thermohaline Circulation ◽

Deep Convection ◽

Ice Cover ◽

Snow Accumulation ◽

Heat Fluxes ◽

Weddell Sea ◽

Salt Flux ◽

Ice Formation ◽

Atmospheric Conditions

AbstractDuring a field experiment in July 1994, while the R.V. Nathaniel B. Palmer was moored to a drifting ice floe in the Weddell Sea, Antarctica, data were collected on sea-ice and snow characteristics. We report on the evolution of ice which grew in a newly opened lead. As expected with cold atmospheric conditions, congelation ice initially formed in the lead. Subsequent snow accumulation and large ocean heat fluxes resulted in melt at the base of the ice, and enhanced flooding of the snow on the ice surface. This flooded snow subsequently froze, and, 5 days after the lead opened, all the congelation ice had melted and 26 cm of snow ice had formed. We use measured sea-ice and snow salinities, thickness and oxygen isotope values of the newly formed lead ice to calculate the salt flux to the ocean. Although there was a salt flux to the ocean as the ice initially grew, we calculate a small net fresh-wlter input to the upper ocean by the end of the 5 day period. Similar processes of basal melt and surface snow-ice formation also occurred on the surrounding, thicker sea ice. Oceanographic studies in this region of the Weddell Sea have shown that salt rejection by sea-ice formation may enhance the ocean vertical thermohaline circulation and release heat from the deeper ocean to melt the ice cover. This type of deep convection is thought to initiate the Weddell polynya, which was observed only during the 1970s. Our results, which show that an ice cover can form with no salt input to the ocean, provide a mechanism which may help explain the more recent absence of the Weddell polynya.

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Separating the influences of low-latitude warming and sea-ice loss on Northern Hemisphere climate change

Journal of Climate ◽

10.1175/jcli-d-21-0180.1 ◽

2022 ◽

pp. 1-59

Author(s):

Paul J. Kushner ◽

Russell Blackport ◽

Kelly E. McCusker ◽

Thomas Oudar ◽

Lantao Sun ◽

...

Keyword(s):

Sea Ice ◽

Arctic Ocean ◽

Northern Hemisphere ◽

North Atlantic ◽

High Latitude ◽

North Pacific ◽

Heat Fluxes ◽

The Arctic ◽

Low Latitude ◽

The Arctic Ocean

Abstract Analyzing a multi-model ensemble of coupled climate model simulations forced with Arctic sea-ice loss using a two-parameter pattern-scaling technique to remove the cross-coupling between low- and high-latitude responses, the sensitivity to high-latitude sea-ice loss is isolated and contrasted to the sensitivity to low-latitude warming. In spite of some differences in experimental design, the Northern Hemisphere near-surface atmospheric sensitivity to sea-ice loss is found to be robust across models in the cold season; however, a larger inter-model spread is found at the surface in boreal summer, and in the free tropospheric circulation. In contrast, the sensitivity to low-latitude warming is most robust in the free troposphere and in the warm season, with more inter-model spread in the surface ocean and surface heat flux over the Northern Hemisphere. The robust signals associated with sea-ice loss include upward turbulent and longwave heat fluxes where sea-ice is lost, warming and freshening of the Arctic ocean, warming of the eastern North Pacific relative to the western North Pacific with upward turbulent heat fluxes in the Kuroshio extension, and salinification of the shallow shelf seas of the Arctic Ocean alongside freshening in the subpolar North Atlantic. In contrast, the robust signals associated with low-latitude warming include intensified ocean warming and upward latent heat fluxes near the western boundary currents, freshening of the Pacific Ocean, salinification of the North Atlantic, and downward sensible and longwave fluxes over the ocean.

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Arctic Intense Summer Storms and Their Impacts on Sea Ice—A Regional Climate Modeling Study

Atmosphere ◽

10.3390/atmos10040218 ◽

2019 ◽

Vol 10 (4) ◽

pp. 218 ◽

Cited By ~ 4

Author(s):

Alexander Semenov ◽

Xiangdong Zhang ◽

Annette Rinke ◽

Wolfgang Dorn ◽

Klaus Dethloff

Keyword(s):

Sea Ice ◽

Climate Model ◽

Chukchi Sea ◽

Regional Climate ◽

Turbulent Fluxes ◽

Heat Fluxes ◽

Shortwave Radiation ◽

Energy Budgets ◽

Sea Ice Concentration ◽

Storm Activity

Various temporal and spatial changes have manifested in Arctic storm activities, including the occurrence of the anomalously intense storms in the summers of 2012 and 2016, along with the amplified warming and rapidly decreased sea ice. To detect the variability of and changes in storm activity and understand its role in sea ice changes, we examined summer storm count and intensity year-by-year from ensemble hindcast simulations with an Arctic regional coupled climate model for the period of 1948–2008. The results indicated that the model realistically simulated the climatological spatial structure of the storm activity, characterized by the storm count and intensity. The simulated storm count captures the variability derived from the National Centers for Environmental Prediction-National Center for Atmospheric Research (NCEP–NCAR) reanalysis, though the simulated one is higher than that in the reanalysis. This could be attributed to the higher resolution of the model that may better represent smaller and shallower cyclones. The composite analysis shows that intense storms tend to form a low-pressure pattern with centers over the Kara Sea and Chukchi Sea, respectively, generating cyclonic circulation over the North Atlantic and North Pacific Arctic Ocean. The former drives intensification of the transpolar drift and Fram Strait sea ice export, and the latter suppresses thick ice transport from the Canada Basin to the Beaufort–Chukchi Seas, in spite of an increase in sea ice transport to the East Siberian Sea. Associated with these changes in sea ice transport, sea ice concentration and thickness show large decreases in the Barents–Kara Seas and the Chukchi–East-Siberian Seas, respectively. Energy budgets analysis suggests that more numerous intense storms substantially decrease the downward net sea ice heat fluxes, including net radiative fluxes, turbulent fluxes, and oceanic heat fluxes, compared with that when a lower number of intense storms occur. The decrease in the heat fluxes could be attributable to an increased cloudiness and the resultant reduction of downward shortwave radiation, as well as a destabilized boundary layer induced increase in upward turbulent fluxes.

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Identification and tracking of individual sea ice floes from ENVISAT wide swath SAR images: a case study from Fram Strait

Remote Sensing Letters ◽

10.1080/01431161.2011.583288 ◽

2012 ◽

Vol 3 (4) ◽

pp. 295-304 ◽

Cited By ~ 1

Author(s):

Jennifer A. Hall ◽

Grant R. Bigg ◽

Richard Hall

Keyword(s):

Sea Ice ◽

Fram Strait ◽

Sar Images ◽

Ice Floes ◽

Wide Swath

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Pancake sea ice kinematics and dynamics using shipboard stereo video

Annals of Glaciology ◽

10.1017/aog.2019.35 ◽

2019 ◽

Vol 61 (82) ◽

pp. 1-11 ◽

Cited By ~ 1

Author(s):

Madison Smith ◽

Jim Thomson

Keyword(s):

Sea Ice ◽

Energy Loss ◽

Wave Energy ◽

Wave Attenuation ◽

Bulk Wave ◽

Ocean Turbulence ◽

Stereo Video ◽

Ice Floes ◽

Turbulence Generation

AbstractIn the marginal ice zone, surface waves drive motion of sea ice floes. The motion of floes relative to each other can cause periodic collisions, and drives the formation of pancake sea ice. Additionally, the motion of floes relative to the water results in turbulence generation at the interface between the ice and ocean below. These are important processes for the formation and growth of pancakes, and likely contribute to wave energy loss. Models and laboratory studies have been used to describe these motions, but there have been no in situ observations of relative ice velocities in a natural wave field. Here, we use shipboard stereo video to measure wave motion and relative motion of pancake floes simultaneously. The relative velocities of pancake floes are typically small compared to wave orbital motion (i.e. floes mostly follow the wave orbits). We find that relative velocities are well-captured by existing phase-resolved models, and are only somewhat over-estimated by using bulk wave parameters. Under the conditions observed, estimates of wave energy loss from ice–ocean turbulence are much larger than from pancake collisions. Increased relative pancake floe velocities in steeper wave fields may then result in more wave attenuation by increasing ice–ocean shear.

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Numerical Study on Wave-Ice Interaction in the Marginal Ice Zone

Journal of Marine Science and Engineering ◽

10.3390/jmse9010004 ◽

2020 ◽

Vol 9 (1) ◽

pp. 4

Author(s):

Tiecheng Wu ◽

Wanzhen Luo ◽

Dapeng Jiang ◽

Rui Deng ◽

Shuo Huang

Keyword(s):

Sea Ice ◽

Numerical Study ◽

Test Results ◽

Towing Tank ◽

Marginal Ice Zone ◽

Computational Fluid Dynamics Cfd ◽

Numerical Research ◽

Ice Floes ◽

Cfd Method ◽

Six Degree Of Freedom

The effect of waves on ice sheet is critical in the marginal ice zone (MIZ). Waves break large sea ice into small pieces and cause them to collide with each other. Simultaneously, the interaction between sea ice and waves attenuates these waves. In this study, a numerical research is conducted based on a computational fluid dynamics (CFD) method to investigate the response of single ice floe to wave action. The obtained results demonstrate that the sea ice has a violent six degree of freedom (6DoF) motion in waves. Ice floes with different sizes, thicknesses, and shapes exhibit different 6DoF motions under the action of waves. The heave and surge response amplitude operator (RAO) of the sea ice are related to wavelength. Furthermore, the overwash phenomenon can be observed in the simulation. The obtained results are compared with the model test in the towing tank based on artificial ice, and they agree well with test results.

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