Abstract
The variation of Ross Ice Shelf Polynya (RISP) ice production is a synergistic result of several factors. This study aims to analyze the 2003–2017 RISP ice production time series with respect to the impact of wind forcing on heat flux sources. RISP ice production was estimated from passive microwave sea ice concentration images and reanalysis meteorological data using a thermodynamic model. The total ice production was divided into four components according to the amount of ice produced by different heat fluxes: solar radiation component (Vs), longwave radiation component (Vl), sensible heat flux component (Vfs), and latent heat flux component (Vfe). The results show that Vfs made the largest contribution, followed by Vl and Vfe, while Vs had a negative contribution. Our study reveals that total ice production and Vl, Vfs, and Vfe highly correlated with the RISP area size, whereas Vs negatively correlated with the RISP area size in October, and had a weak influence from April to September. Since total ice production strongly correlates with the polynya area and this significantly correlates with the wind speed of the previous day, strong wind events lead to sharply increased ice production most of the time. Strong wind events, however, may only lead to mildly increasing ice production in October, when enlarged Vs reduces the ice production. Wind speed influences ice production by two mechanisms: impact on polynya area, and impact on heat exchange and phase transformation of ice. Vfs and Vfe are influenced by both mechanisms, while Vs and Vl are only influenced by impact on polynya area. These two mechanisms show different degrees of influence on ice production during different periods. Persistent offshore winds were responsible for the large RISP area and high ice production in October 2005 and June 2007.
Highlights
Polynyas are isolated open water areas surrounded by ice packs [1]
By using heat flux sources analysis, we estimated that sensible heat flux Vfs accounted for 60.1% of the total ice production, followed by longwave radiation Vl accounting for 26.9% and latent heat flux Vfe accounting for 20.4%, and solar radiation Vs accounted for −7.5%
The sensible heat flux component Vfs accounted for 60.1% of the total ice production, the longwave radiation component Vl for 26.9%, the latent heat flux component Vfe for 20.4%, the solar radiation component Vs for -7.5% which decreased to -54.9% in October
Summary
Known as latent heat polynyas, are formed by divergent ice motion, and are driven and maintained by prevailing winds or oceanic currents. The Ross Ice Shelf Polynya (RISP) is the largest coastal polynya over the Southern Ocean, with the highest sea ice production [4,5]. It has been regarded as an important source of Antarctic bottom water [6,7]. Polynya formation and ice production are related to a variety of environmental factors, including atmospheric forcing, currents, tides, air and ocean temperature, landfast ice, and iceberg drift [1,8,9,10,11]
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