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This suggest that the increasing trend in sea ice speed is due to increased response to winds by a thinner ice cover (see below). A trend toward faster moving ice has been noted, but wind speeds have not increased. However, local and small-scale features, such as divergent motions opening up cracks (leads) in the ice are not accurately retrieved in passive microwave derived fields. Implementing such approaches yields a generally smooth motion field that can accurately track large-scale sea ice circulation ( Fig. And spatial interpolation and temporal averaging over several days can reduce this further. Oversampling can reduce this down to ~ 3–4 km/day. However, the precision of the tracking is limited by the low spatial resolution of the imagery-a feature either stays in its original grid cell or moves to an adjacent grid cell, meaning that in a 12.5 km gridded resolution image, the motion is discretized into 12.5 km/day bins, resulting a very “noisy” motion field.
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Using passive microwave imagery to track sea ice motion is advantageous because of the all-sky capabilities.
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As D→Λ, discontinuities build up, and as D→ d we have a set of n individual floes. For continuum models to be valid for a floe field, the size of continuum material particles D must satisfy d< D<Λ, where Λ is the gradient length scale. Ice floes are described by their thickness h and diameter d, and we may examine the drift of an individual floe or a field of floes. The horizontal structure of a sea ice cover is well revealed by optical satellite images ( Figure 1(a)). They influence the mesoscale ocean dynamics resulting in ice edge eddies, jets, and upwelling/downwelling. Well-developed MIZs are found along the oceanic ice edge of the polar oceans. It is loosely characterized as the zone, which ‘feels the presence of the open ocean’ and extends to a distance of 100 km from the ice edge. Marginal ice zone (MIZ) lies along the boundary to open sea. Next to fast ice is the shear zone (width 10–200 km), where the mobility of the ice is restricted by the geometry of the boundary and strong deformation takes place. Land fast or fast ice is the immobile coastal sea ice zone extending from the shore to about 10–20-m depths (in Antarctic, grounded icebergs may act as tie points and extend the fast ice zone to deeper waters).
#Open water drift 2 free
The central pack is free from immediate influence from the boundaries, and the length scale is the size of the basin. It can be divided into zones of different dynamic character. (c) Sea ice landscape from the Weddell Sea, Antarctica, showing a first-year ice floe field.Ī sea ice landscape consists of ice floes with ridges and other morphological features, and leads and polynyas.
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(b) Sea ice landscape of the heavy pack ice in the Arctic Ocean, north of Svalbard. (a) A moderate-resolution imaging spectroradiometer (MODIS) image (NASA’s Terra/Aqua satellite) of the sea ice cover in the Gulf of Riga, 3 Mar.