let's not forget the new paper looking at long wave radiation and finding that 'opaque' skies are better than 'clear skies' for imparting energy to the snow/ice below?
only as it relates to melt onset. Warm, moist air is better at getting the ice/snow surface to melt for the first time .. After melt onset, short-wave radiation is more effective at building up melting momentum if I've interpreted the paper correctly.
Not if that new paper is the one below. This research only addresses melt onset. There is a single very familiar sentence midway on sunlight being ineffectual until melt (or whatever) has decreased albedo, not any comparison of effectiveness. Clouds are complex and counterintuitive.
It reminds me of the record July 2012 melt-out of Greenland -- that too is attributed to cloud cover (of just the right kind), not sunny skies. And this year's shocking melt came far too early for such attribution.
http://tinyurl.com/zp6xhhaMelt onset over Arctic sea ice controlled by atmospheric moisture transport
J Mortin ... JC. Stroeve et al
http://tinyurl.com/j2q2hs5 free full
The timing of melt onset affects the surface energy uptake throughout the melt season. Yet the processes triggering melt and causing its large interannual variability are not well understood. Here, we show that melt onset over Arctic sea ice is initiated by positive anomalies of water vapor, clouds, and air temperatures that increase the downwelling longwave radiation (LWD) to the surface. The earlier melt onset occurs, the stronger are these anomalies. Downwelling shortwave radiation (SWD) is smaller than usual at melt onset, indicating that melt is not triggered by SWD.
When melt occurs early, an anomalously opaque atmosphere with positive LWD anomalies preconditions the surface for weeks preceding melt. In contrast, when melt begins late, clearer than usual conditions are evident prior to melt. Hence, atmospheric processes are imperative for melt onset. It is also found that spring LWD increased during recent decades, consistent with trends towards an earlier melt onset.
The seasonal transition from winter to summer plays an important role for the Arctic climate. The timing of sea ice melt onset affects the energy absorbed by the surface throughout the summer melt season, because after melt begins, the albedo continues to decrease until either the sea ice is completely melted and disappears or freeze-up has begun.
Over multi year ice, for any day melt begins earlier, additional energy sufficient to melt 3 cm of sea ice during the melt season is absorbed [Perovich et al., 2007]. Since melt onset has been occurring successively earlier over the last few decades, the
energy uptake over the Arctic Ocean in summer has increased by an amount large enough to melt about 1 m of ice over a recent 5-year period [Stroeve 2014
http://tinyurl.com/h5zurgz].
This additional energy warms the ocean during summer, leading to a substantially later fall freeze-up and a warmer lower atmosphere in the fall.Hereby the atmospheric circulation, both within and outside of the Arctic region, may be altered
...
At a specific site and a certain year, the
melt onset was found to be triggered by moist, warm air masses associated with synoptic-scale weather systems that augmented the atmospheric energy fluxes to the surface... Arctic melt onset is
weakly linked to two atmospheric circulation indicators, the Arctic oscillation and the 500-hPa height.
The increased cloudiness leads to a reduction of downwelling shortwave radiation at the surface (SWD). These findings imply that
the enhanced greenhouse effect associated with more [imported, non-local] moisture and clouds in the atmosphere is crucial for the timing of the melt onset over sea ice. Further, SWD in itself seems of minor importance for triggering melt.
After melt is initiated, however, the importance of the SWD increases as the albedo of the sea-ice surface decreases and more solar radiation is absorbed by the surface.