Spatio-temporal variability of polynya dynamics and ice production in the Laptev Sea between the winters of 1979/80 and 2007/08

Abstract

Polynyas in the Laptev Sea are examined with respect to recurrence and interannual wintertime ice production. We use a polynya classification method based on passive microwave satellite data to derive daily polynya area from long-term sea-ice concentrations. This provides insight into the spatial and temporal variability of open-water and thin-ice regions on the Laptev Sea Shelf. Using thermal infrared satellite data to derive an empirical thin-ice distribution within the thickness range from 0 to 20 cm, we calculate daily average surface heat loss and the resulting wintertime ice formation within the Laptev Sea polynyas between 1979 and 2008 using reanalysis data supplied by the National Centers for Environmental Prediction, USA, as atmospheric forcing. Results indicate that previous studies significantly overestimate the contribution of polynyas to the ice production in the Laptev Sea. Average wintertime ice production in polynyas amounts to approximately 55 km3±27% and is mostly determined by the polynya area, wind speed and associated large-scale circulation patterns. No trend in ice production could be detected in the period from 1979/80 to 2007/08

Variability and trends in Laptev Sea ice outflow between 1992–2011

“…The model is derived from the data overlapping period (2002)(2003)(2004)(2005)(2006)(2007)(2008). A detailed description of the methodology is given in Willmes et al (2011). The comparison of ice area flux in late winter/early spring with summer ice anomalies of the following summer reveals a negative coupling that support our assumption (Fig.…”

“…In the following, we will focus on the potential linkage that exists between presence/absence of extensive thin ice areas in late winter and the occurrence of low/high summer ice extent. Thin ice areas can be derived directly from AMSR-E and SSM/I scenes, using the Polynya Signature Simulation Method (PSSM, Markus and Burns, 1995;Kern, 2009;Willmes et al, 2011). The method provides a classification of thin ice and open water (polynya area) and is based on the sensitivity of passive microwave polarization ratios to ice thickness in the range of 0-20 cm (Willmes et al, 2010).…”

“…Thin ice areas can be derived directly from AMSR-E and SSM/I scenes, using the Polynya Signature Simulation Method (PSSM, Markus and Burns, 1995;Kern, 2009;Willmes et al, 2011). The method provides a classification of thin ice and open water (polynya area) and is based on the sensitivity of passive microwave polarization ratios to ice thickness in the range of 0-20 cm (Willmes et al, 2010). However, the coarse spatial resolution of passive microwave satellite data, in particular if applied to narrow polynyas or polynyas formed during extremely cold periods, generates errors through mixed signals at the fast and pack-ice edges, and results in underestimating the thin ice and open water area (Willmes et al, 2010;Krumpen et al, 2011b).…”

Origin of freshwater and polynya water in the Arctic Ocean halocline in summer 2007

“…Studies from the south-eastern Laptev Sea already revealed unusually wide and late polynya openings in April 2007 (Willmes et al, 2011), which were not effective in the formation of brine-enriched bottom water (Bauch et al, 2010) usually observed with salinity of about 30 (Bauch et al, 2005). Further studies have to investigate which pattern will be more prominent in the future and how this may affect the Arctic Ocean halocline.…”

“…Because of this decline in ice cover, large areas of the ocean especially on the shelves have been free of sea-ice for prolonged periods of time. Climatic changes may have an impact on the freshwater balance of the Arctic Ocean (Dickson et al, 2007;Rabe et al, 2011) and the change in sea-ice cover may specifically influence the occurrence of coastal polynyas and thus, the amount of sea-ice formed there (Willmes et al, 2011). Therefore, in order to further understand possible consequences and feedbacks of the current and future changes, it is of fundamental importance to get a more detailed understanding of the Arctic system and to identify sources of the Arctic Ocean halocline waters with respect to regions and processes of formation.…”