Sea-ice thickness from field measurements in the northwestern Barents Sea

Abstract

The Barents Sea is one of the fastest changing regions of the Arctic, and has experienced the strongest decline in winter‐time sea‐ice area in the Arctic, at −23±4% decade−1. Sea‐ice thickness in the Barents Sea is not well studied. We present two previously unpublished helicopter‐borne electromagnetic (HEM) ice thickness measurements from the northwestern Barents Sea acquired in March 2003 and 2014. The HEM data are compared to ice thickness calculated from ice draft measured by ULS deployed between 1994 and 1996. These data show that ice thickness varies greatly from year to year; influenced by the thermodynamic and dynamic processes that govern local formation vs long‐range advection. In a year with a large inflow of sea‐ice from the Arctic Basin, the Barents Sea ice cover is dominated by thick multiyear ice; as was the case in 2003 and 1995. In a year with an ice cover that was mainly grown in situ, the ice will be thin and mechanically unstable; as was the case in 2014. The HEM data allow us to explore the spatial and temporal variability in ice thickness. In 2003 the dominant ice class was more than 2 years old; and modal sea‐ice thickness varied regionally from 0.6 to 1.4 m, with the thinner ice being either first‐year ice, or multiyear ice which had come into contact with warm Atlantic water. In 2014 the ice cover was predominantly locally grown ice less than 1 month old (regional modes of 0.5–0.8 m). These two situations represent two extremes of a range of possible ice thickness distributions that can present very different conditions for shipping traffic; or have a different impact on heat transport from ocean to atmosphere.

Comparison of ERA5 and ERA-Interim near-surface air temperature, snowfall and precipitation over Arctic sea ice: effects on sea ice thermodynamics and evolution

“…ERA-I is known to have an anomalously large fraction of liquid precipitation (rain) and thus low snowfall to precipitation ratio in the Arctic, especially during August-September (Dutra et al, 2011;Leeuw et al, 2015). The total precipitation accumulated along the buoy drift trajectories, during the cold season (from 15 August or 1 October until a buoy fails or until 30 April), was higher in ERA5 than in ERA-I for every buoy examined.…”

“…The low SF / TP ratio and thus larger fraction of rainfall in ERA-I is known to be anomalous, and is likely due to the cloud physics scheme used (e.g. Dutra et al, 2011;Leeuw et al, 2015). In ERA-I, the split between liquid and ice in clouds is determined diagnostically as a function of temperature from −23 to 0 • C, with ice only below −23 • C and liquid only above 0 • C. In contrast, the IFS Cy41r2 used in ERA5 includes a prognostic microphysics scheme, with separate cloud liquid, cloud ice, rain and snow prognostic variables (Sotiropoulou et al, 2015; see also ECMWF IFS documentation -Cy41r2; https://www.ecmwf.int/sites/default/files/ elibrary/2016/16648-part-iv-physical-processes.pdf, last access: 4 March 2019).…”

A weekly Arctic sea-ice thickness data record from merged CryoSat-2 and SMOS satellite data

“…Between 19 and 26 March, eight AEM flights were carried out by a helicopter based on the Norwegian research vessel Lance ( Fig. 13b; King et al, 2017). In contrast to the Beaufort Sea data, these data contain first-year ice only.…”

Thin Sea Ice, Thick Snow, and Widespread Negative Freeboard Observed During N‐ICE2015 North of Svalbard

“…Field studies and direct observations allow the investigation of the composition of ice types , the amount and structure of the snow cover Webster et al, 2014), and the seasonal changes in ice and snow thickness Wang et al, 2016). Regional (e.g., Hansen et al, 2013;King et al, 2017;Renner et al, 2013Renner et al, , 2014 and local studies (Gerland et al, 2008) in the European sector of the Arctic Ocean have shown a thinning of sea-ice coherent with that documented on a pan-Arctic scale.…”