Long-Term Analysis of Sea Ice Drift in the Western Ross Sea, Antarctica, at High and Low Spatial Resolution

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.

Sea Ice Thickness in the Western Ross Sea

“…The increasing trend in Ross Sea ice extent is highest for winter and spring (Parkinson, 2019), during a period when very thick sea ice of the western region is exported to the north. Near coastal reanalysis of wind and high‐resolution sea ice drift in this area has been shown to be underestimated (Dale et al., 2017; Farooq et al., 2020), processes which are important to understand the thickness distribution we have observed. Large scale sea ice models need to be evaluated against observations and processes described in this study in order to fully explain volume trends in this region of sea ice growth.…”

The Salinity Budget of the Ross Sea Continental Shelf, Antarctica

“…The total sea ice production over the shelf in this study is much larger than that derived from the observations (Drucker et al., 2011; Silvano et al., 2020). At present, there are large deviations between different observational data of sea ice thickness (Rack et al., 2021) or different observational data of sea ice drift (Farooq et al., 2020; Haumann et al., 2016). These can result in great uncertainties in the estimated sea ice productions over the shelf.…”

“…The sea ice thickness, for example, could even be greater than 2 m in the western Ross Sea in November 2017 (Rack et al, 2021). Also, Farooq et al (2020) indicated that the error in the sea ice motion vector in the Ross Sea continental shelf could be as large as 47%. In addition, the simulated average sea ice thickness at the shelf break is 1.2 m, which is much greater than the value of 0.6 ± 0.3 m used in Drucker et al (2011).…”

Delineating Polynya Area Using Active and Passive Microwave Sensors for the Western Ross Sea Sector of Antarctica

“…Manual identification of polynyas is subjective as well as time-consuming, yet it is a common way to validate [35] the generated results from objective classifications. HHpolarization is preferable for sea ice mapping as ocean clutter is suppressed.…”