Wave climate in the Arctic 1992–2014: seasonality and trends

Abstract

Abstract. Over the past decade, the diminishing Arctic sea ice has impacted the wave field, which depends on the icefree ocean and wind. This study characterizes the wave climate in the Arctic spanning 1992-2014 from a merged altimeter data set and a wave hindcast that uses CFSR winds and ice concentrations from satellites as input. The model performs well, verified by the altimeters, and is relatively consistent for climate studies. The wave seasonality and extremes are linked to the ice coverage, wind strength, and wind direction, creating distinct features in the wind seas and swells. The altimeters and model show that the reduction of sea ice coverage causes increasing wave heights instead of the wind. However, trends are convoluted by interannual climate oscillations like the North Atlantic Oscillation (NAO) and Pacific Decadal Oscillation. In the Nordic Greenland Sea the NAO influences the decreasing wind speeds and wave heights. Swells are becoming more prevalent and windsea steepness is declining. The satellite data show the sea ice minimum occurs later in fall when the wind speeds increase. This creates more favorable conditions for wave development. Therefore we expect the ice freeze-up in fall to be the most critical season in the Arctic and small changes in ice cover, wind speeds, and wave heights can have large impacts to the evolution of the sea ice throughout the year. It is inconclusive how important wave-ice processes are within the climate system, but selected events suggest the importance of waves within the marginal ice zone.

A two layer model for wave dissipation in sea ice

“…This parameterization compared well with available field observations in the MIZ at the time (Wadhams et al, 1988) with an eddy viscosity under the ice between 2 and 4 orders of magnitude greater than the molecular value for sea water. While this model has been shown to also compare well with later observations (Sutherland & Gascard, 2016;Rabault et al, 2017), it does require the fitting of an eddy viscosity, which is required to vary by several orders of magnitude to be consistent with observations and such large values may not be physically realistic (Stopa, 2016). More recently, and Marchenko et al (2018) extended the theory of Weber (1987) to account for a partial-slip boundary condition and to include floe-floe interactions.…”

Episodic Reversal of Autumn Ice Advance Caused by Release of Ocean Heat in the Beaufort Sea

“…Large expanses of open water in the summer Arctic Ocean in recent years allow winds to form large swells that propagate into the ice pack (Asplin et al, 2012(Asplin et al, , 2014. Observations of discrete large wave events (Asplin et al, 2012;Collins et al, 2015;Thomson & Rogers, 2014) are indicative of a general shift in the wave climate toward larger waves in the Beaufort Sea (Stopa, 2016;Thomson et al, 2016). The extent to which the increasing wave climate has enhanced mixing in the surface waters, via mechanisms such as Langmuir turbulence (D'Asaro et al, 2014), is not known.…”

Effects of changing permafrost and snow conditions on tundra wildlife: critical places and times

“…Second, changes in wind speed modify the hardness of wind slabs and their ability to support travel (Kotlyakov 1961). Since wind speeds have overall been observed and predicted to increase in the coastal Arctic (Steiner et al 2015;Stopa et al 2016), partly because of the late freezeup that increases the thermal contrast between land and ocean, snow hardness is expected to increase. Third, episodes of temperatures above 0°C lead to the formation of melt-freeze crusts at the top of the snowpack (Jamieson 2006).…”