Surface energy budget of landfast sea ice during the transitions from winter to snowmelt and melt pond onset: The importance of net longwave radiation and cyclone forcings

Abstract

Relatively few sea ice energy balance studies have successfully captured the transition season of warming, snowmelt, and melt pond formation. In this paper, we report a surface energy budget for landfast sea ice that captures this important period. The study was conducted in the Canadian Arctic Archipelago from 10 May to 20 June 2010. Over the first 20 days of the study, we found that short periods (1-3 days) of increased net radiation associated with low longwave loss provided most of the energy required to warm the snowpack from winter conditions. An extended period of low longwave loss (5 days) combined with the seasonal increase in incoming shortwave radiation then triggered snowmelt onset. Melt progressed with a rapid reduction in albedo and attendant increases in shortwave energy absorption, resulting in melt pond formation 8 days later. The key role of longwave radiation in initiating melt onset supports past findings, and confirms the importance of clouds and water vapor associated with synoptic weather systems. However, we also observed a period of strong turbulent energy exchange associated with the passage of a cyclone. The cyclone event occurred shortly after melt pond formation, but it delivered enough energy to significantly hasten melt onset had it occurred earlier in the season. Changes in the frequency, duration, and timing of synoptic-scale weather events that deliver clouds and/or strong turbulent heat fluxes may be important in explaining observed changes in sea ice melt onset timing.

Inorganic carbon system dynamics in landfast Arctic sea ice during the early‐melt period

“…Sea ice thickness (142 ± 2 cm) and freeboard (10 ± 1 cm) remained relatively constant at our sampling site over the duration of this study. Temperatures in bulk ice and brine (Figures c and e) increased as surface air T increased from an average of −12°C in early May to around 0°C in early June [ Else et al ., ]. Sea ice T exhibited a minimum of around −7°C at the ice surface at the beginning of the program, corresponding to high bulk ice S of 6.3–9.6 (Figures c and d).…”

Winter observations of CO<sub>2</sub> exchange between sea ice and the atmosphere in a coastal fjord environment

“…Following e.g., Else et al (2014) and Persson (2012), the surface energy balance of snow overlaying sea ice may be written as…”

The regional influence of the Arctic Oscillation and Arctic Dipole on the wintertime Arctic surface radiation budget and sea ice growth

“…Downwelling LW radiation at the surface responds to changes in clouds and the temperature and water vapor content of the atmospheric column above the surface, especially in the lower troposphere [e.g., Sedlar and Devasthale, 2012]. Individually, warm/moister air intrusions generally reduce sea ice concentration and thickness [Park et al, 2015;Boisvert et al, 2016] playing an important role in the winter-spring transition defined as the melt onset [Persson, 2012;Else et al, 2014;Mortin et al, 2016;Hegyi and Deng, 2017]. Individually, warm/moister air intrusions generally reduce sea ice concentration and thickness [Park et al, 2015;Boisvert et al, 2016] playing an important role in the winter-spring transition defined as the melt onset [Persson, 2012;Else et al, 2014;Mortin et al, 2016;Hegyi and Deng, 2017].…”