Recent observations of superimposed ice and snow ice on sea ice in the northwestern Weddell Sea

Abstract

Abstract. Recent low summer sea ice extent in the Weddell Sea raises questions about the contributions of dynamic and thermodynamic atmospheric and oceanic energy fluxes. The roles of snow, superimposed ice, and snow ice are particularly intriguing, as they are sensitive indicators for changes in atmospheric forcing, and as they could trigger snow-albedo feedbacks that could accelerate ice melt. Here we present snow depth data and ice core observations of superimposed ice and snow ice collected in the northwestern Weddell Sea in late austral summer of 2019, supplemented by airborne ice thickness measurements. Texture, salinity, and oxygen isotope analyses showed mean thicknesses of superimposed and snow ice of 0.11 ± 0.11 m and 0.22 ± 0.22 m, respectively, or 3 to 54 % of total ice thickness. Mean snow depths ranged between 0.46 ± 0.29 m in the south to 0.05 ± 0.06 m in the north, with mean and modal, total ice thicknesses between 4.12 ± 1.87 m to 1.62 ± 1.05 m, and 3.9 m to 0.9 m, respectively. These snow and ice properties are similar to results from previous studies, suggesting that the ice’s summer surface energy balance and related seasonal transition of snow properties have changed little in past decades. This is supported by our additional analyses of the summer energy balance using atmospheric reanalysis data, and melt onset observations from satellite scatterometry showing little recent changes.

Sensitivity of Sea Ice Growth to Snow Properties in Opposing Regions of the Weddell Sea in Late Summer

“…All ERA5 data from ECMWF are accessed and downloaded from the Copernicus Climate Change Service (last access: 11 August 2021): https://cds.climate.copernicus.eu/cdsapp#!/dataset/reanalysis-era5-single-levels?tab=form. All presented field data are archived in PANGAEA with the following references: Arndt (2022b) and Arndt and Haas (2021, 2022c) for snow depth data, Arndt (2021, 2022a), and Arndt and Hass (2022b) for snow stratigraphy, and Arndt (2022c) and Arndt and Haas (2022a, 2022b), for SnowMicroPen data. Snow accumulation measurements from Snow Buoys were obtained from https://www.meereisportal.de (grant: REKLIM‐2013‐04) and are stored in PANGAEA (Nicolaus et al., 2017).…”