Contribution of Deformation to Sea Ice Mass Balance: A Case Study From an N‐ICE2015 Storm

Abstract

The fastest and most efficient process of gaining sea ice volume is through the mechanical redistribution of mass as a consequence of deformation events. During the ice growth season divergent motion produces leads where new ice grows thermodynamically, while convergent motion fractures the ice and either piles the resultant ice blocks into ridges or rafts one floe under the other. Here we present an exceptionally detailed airborne data set from a 9 km2 area of first year and second year ice in the Transpolar Drift north of Svalbard that allowed us to estimate the redistribution of mass from an observed deformation event. To achieve this level of detail we analyzed changes in sea ice freeboard acquired from two airborne laser scanner surveys just before and right after a deformation event brought on by a passing low‐pressure system. A linear regression model based on divergence during this storm can explain 64% of freeboard variability. Over the survey region we estimated that about 1.3% of level sea ice volume was pressed together into deformed ice and the new ice formed in leads in a week after the deformation event would increase the sea ice volume by 0.5%. As the region is impacted by about 15 storms each winter, a simple linear extrapolation would result in about 7% volume increase and 20% deformed ice fraction at the end of the season.

A Distributed Snow‐Evolution Model for Sea‐Ice Applications (SnowModel)

“…These plots present SWE depletion of the entire snowpack, after the snowpack ripening (becoming isothermal at 0°C) was complete; this ripening resulted in a 1 day melt‐onset delay for the SYI floe over the FYI floe. These snowmelt rates are similar to those measured by autonomous ice mass balance buoys in the same general area (Perovich et al, ), and those measured on other N‐ICE2015 floes (Itkin et al, ).…”

“…Other N‐ICE2015 Floes had higher pressure ridges. For example, pressure ridges over 1.5 m high (on a 5 m grid) were measured on Floe‐3 using an airborne laser scanner (Itkin et al, ; King et al, ), and ground‐based lidar scans on Floe‐3 and Floe‐4 measured average ridge heights of approximately 1.6 m, and 1.4 m above sea level, respectively.…”

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

“…The data acquired by five IMBs, a snow buoy, hotwire, and snow‐stake fields associated with Floe 1 and its surrounding represent different snow and ice conditions observed during the drift. All buoys show a weak increase in ice thickness during a period of low air temperatures in the last week of January, followed by an increase of snow depth from 0.59 to 0.66 m for SIMBA_2015a and a decrease from 0.45 to 0.35 m for SIMBA_2015b (Itkin et al, ). During a major storm event lasting from 3 to 8 February (M2) (Cohen et al, ), snow depth at SIMBA_2015b and SIMBA_2015g decreased, while it increased at SIMBA_2015e.…”

“…All sensors are sheltered in a floating elongated tube that should potentially survive summer melt and fall freeze‐up processes. During N‐ICE2015, in total four snow buoys, seven SIMBAs, one IMB‐B, and one IMB‐S provided reliable data (Table ; Itkin et al, ). On Floes 1–3 , the four snow buoys were always deployed with a colocated thermistor IMB.…”

Observations of flooding and snow‐ice formation in a thinner Arctic sea‐ice regime during the N‐ICE2015 campaign: Influence of basal ice melt and storms

“…In particular we acknowledge support from the ANR EQUIPEX IAOOS project, through ANR‐10‐EQPX‐32‐01 grant, and the ICE‐ARC programme from the European Union 7th Framework Programme, grant 603887. The SIMBA data are available in Itkin et al [] and C. Provost (cp@locean-ipsl.upmc.fr).…”