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Abstract
The Ross Sea region, including three main polynya areas in McMurdo Sound, Terra Nova Bay, and in front of the Ross Ice Shelf, has experienced a significant increase in sea ice extent in the first four decades of satellite observations. Here, we use Co-Registration of Optically Sensed Images and Correlation (COSI-Corr) to estimate 894 high-resolution sea ice motion fields of the Western Ross Sea in order to explore ice-atmosphere interactions based on sequential high-resolution Advanced Synthetic Aperture Radar (ASAR) images from the Envisat satellite acquired between 2002–2012. Validation of output motion vectors with manually drawn vectors for 24 image pairs show Pearson correlation coefficients of 0.92 ± 0.09 with a mean deviation in direction of −3.17 ± 6.48 degrees. The high-resolution vectors were also validated against the Environment and Climate Change Canada sea ice motion tracking algorithm, resulting in correlation coefficients of 0.84 ± 0.20 and the mean deviation in the direction of −0.04 ± 17.39 degrees. A total of 480 one-day separated velocity vector fields have been compared to an available NSIDC low-resolution sea ice motion vector product, showing much lower correlations and high directional differences. The high-resolution product is able to better identify short-term and spatial variations, whereas the low-resolution product underestimates the actual sea ice velocities by 47% in this important near-coastal region. The large-scale pattern of sea ice drift over the full time period is similar in both products. Improved image coverage is still desired to capture drift variations shorter than 24 h.
Highlights
Sea ice thermodynamic and dynamic processes play an important role in the global climate as they significantly influence the Earth’s energy balance and the freshwater flux [1]
There is a lack of sea ice drift information at high spatial resolution in this area, and this study addresses this gap and emphasizes the importance of high-resolution sea ice drift estimation for short-term analysis
We assessed the potential of high-resolution radar images for sea ice motion derivation and provide an intrinsic reliability measure for the low-resolution product
Summary
Sea ice thermodynamic and dynamic processes play an important role in the global climate as they significantly influence the Earth’s energy balance and the freshwater flux [1]. Sea ice drift is a key driver of spatio-temporal variations in sea ice concentration and thickness It is a driver of roughness, surface albedo, moisture, and heat fluxes between the ocean and atmosphere, the freshwater budget, and the sea ice melt and growth rates [2,3]. In the Southern ocean, an overall increasing trend is observed in the sea ice extent over the last few decades with a significant expansion in the Ross Sea region ice, though the last few years potentially show signs of a reversing pattern [5]. The mechanisms of this change are still uncertain. Winds over the Ross Sea have considerably strengthened in recent decades, possibly owing to a combination of natural variability [8,9], stratospheric ozone depletion concentrations, and changes in greenhouse gases [10]
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