Influence of Lead width on the Turbulent Flow Over Sea Ice Leads: Modeling and Parametrization

The release of heat from sea-ice leads is an important component of the heat budget in the Arctic, but the impact of leads on regional scale climate is difficult to assess without information on their distribution in both space and time. Remote sensing of leads using satellite data, specifically AVHRR thermal and Landsat visible imagery, is examined with respect to one lead parameter: lead width. Atmospheric effects are illustrated through the concept of thermal contrast transmittance, where the brightness temperature contrast between leads of various ice thicknesses and the surrounding multi-year ice is simulated using a radiative transfer model. Calculations are made as a function of aerosol, ice crystal precipitation, and cirrus cloud optical depths. For example, at ice crystal optical depths of more than about 1.5 under mean January conditions in the central Arctic, the brightness temperature differences between 2 m and 5 cm thick ice are similar to the ice temperature variability so that there would be insufficient contrast to distinguish a lead from the surrounding ice. The geometrical aspects of the sensor are also simulated by degrading Landsat data so that the effect of sensor field-of-view on retrieved lead width statistics can be assessed. Large leads tend to “grow” with increased pixel size while small leads disappear. Changes in lead width and orientation distributions can readily be seen.

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Enhanced gas fluxes in small sea ice leads and cracks: Effects on CO2exchange and ocean acidification

Journal of Geophysical Research Oceans ◽

10.1002/jgrc.20100 ◽

2013 ◽

Vol 118 (3) ◽

pp. 1195-1205 ◽

Cited By ~ 17

Author(s):

N. S. Steiner ◽

W. G. Lee ◽

J. R. Christian

Keyword(s):

Sea Ice ◽

Ocean Acidification ◽

Gas Fluxes ◽

Ice Leads

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The potential of sea ice leads as a predictor for summer Arctic sea ice extent

The Cryosphere ◽

10.5194/tc-12-3747-2018 ◽

2018 ◽

Vol 12 (12) ◽

pp. 3747-3757 ◽

Cited By ~ 2

Author(s):

Yuanyuan Zhang ◽

Xiao Cheng ◽

Jiping Liu ◽

Fengming Hui

Keyword(s):

Sea Ice ◽

Arctic Region ◽

Strong Relationship ◽

Arctic Sea Ice ◽

The Arctic ◽

Sea Ice Extent ◽

Arctic Sea ◽

Moderate Resolution Imaging Spectroradiometer ◽

Ice Leads ◽

Arctic Sea Ice Extent

Abstract. The Arctic sea ice extent throughout the melt season is closely associated with initial sea ice state in winter and spring. Sea ice leads are important sites of energy fluxes in the Arctic Ocean, which may play an important role in the evolution of Arctic sea ice. In this study, we examine the potential of sea ice leads as a predictor for summer Arctic sea ice extent forecast using a recently developed daily sea ice lead product retrieved from the Moderate-Resolution Imaging Spectroradiometer (MODIS). Our results show that July pan-Arctic sea ice extent can be predicted from the area of sea ice leads integrated from midwinter to late spring, with a prediction error of 0.28 million km2 that is smaller than the standard deviation of the observed interannual variability. However, the predictive skills for August and September pan-Arctic sea ice extent are very low. When the area of sea ice leads integrated in the Atlantic and central and west Siberian sector of the Arctic is used, it has a significantly strong relationship (high predictability) with both July and August sea ice extent in the Atlantic and central and west Siberian sector of the Arctic. Thus, the realistic representation of sea ice leads (e.g., the areal coverage) in numerical prediction systems might improve the skill of forecast in the Arctic region.

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A Simple Parameterization of Ice Leads In a General Circulation Model, and the Sensitivity of Climateto Change in Antarctic Ice Concentration

Annals of Glaciology ◽

10.1017/s0260305500008727 ◽

1990 ◽

Vol 14 ◽

pp. 266-269 ◽

Cited By ~ 30

Author(s):

Ian Simmonds ◽

W.F. Budd

Keyword(s):

Sea Ice ◽

General Circulation Model ◽

General Circulation ◽

Sensible Heat Flux ◽

Weighted Average ◽

Circulation Model ◽

Open Water ◽

Weddell Sea ◽

Antarctic Sea Ice ◽

Ice Leads

We present a simple parameterization of the effect of open leads in a general circulation model of the atmosphere. We consider only the case where the sea ice distribution is prescribed (i.e., not interactive) and the fraction of open water in the ice is also prescribed and set at the same value at all points in the Southern Hemisphere and a different value in the Northern Hemisphere. We approximate the distribution of sea ice over a model “grid box” as a part of the box being covered by solid ice of uniform thickness and the complement of the box consisting of open water at a fixed -1.8 C. Because of the nonlinearity in the flux computations, separate calculations are performed over the solid sea ice and over the open leads. The net fluxes conveyed to the atmosphere over the grid box are determined by performing the appropriate area-weighted average over the two surface types. We report on an experiment designed to assess the sensitivity of the modelled climate to the imposition of a 50% concentration in the winter Antarctic sea ice. Significant warming of up to 6°C takes place in the vicinity of and above the Antarctic sea ice and is associated with significant changes in the zonal wind structure. Pressure reductions are simulated over the sea ice, being particularly marked in the Weddell Sea region, and an anomalous east-west aligned ridge is simulated at about 60°S. Very large changes in the sensible heat flux (in excess of 200 Wm−2) are simulated near the coast of Antarctica.

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