Midsummer Energy Balance for the Southern Seas

Abstract

During a ship voyage from Tasmania to Antarctica in summer 2000/01, radiative and meteorological measurements were continuously made, from which the surface energy budget was calculated. Sea conditions throughout the voyage ranged from open water to broken pack and finally to snow-covered unbroken sea ice in McMurdo Sound. The global radiation increased on average during the trip (to higher latitudes) as we travelled poleward. The net radiation, which was positive (toward the surface) on average, decreased however, mostly due to the increase in surface albedo. For open water, most of the net radiation is used for evapouration (61%), while for broken sea-ice conditions, nearly all energy is used for melting of the sea ice or heating of the ocean (96%). For unbroken snow-covered sea ice, the net radiation lies close to zero, due to the high surface albedo, which reached a mean value of 0.81. The sensible heat flux becomes the largest heat source and nearly all the energy is used for warming of the surface. Finally, a Radarsat image, on which the ship track was visible, was used to compare the ship observations with satellite derived ice types.

Radiative and turbulent surface heat fluxes over sea ice in the western Weddell Sea in early summer

“…This may be the case in many regions, but our results indicate that upward heat fluxes can prevail even without this effect: in only 50% of time the air masses observed at ISPOL came from the Antarctic continent, and even among these cases the air mass usually originated from the west or northwest of the Antarctic Peninsula with the flow controlled by the synoptic‐scale pressure gradient. On the other hand, despite of the prevailing katabatic winds at the McMurdo Sound, Wendler et al [2005] observed downward sensible heat flux.…”

“…In the pioneering studies of Andreas [1985] and Andreas and Makshtas [1985], based on ship observations in October–November 1981, the sensible heat flux was directed from air to snow during northerly winds and from snow to air during southerly winds; the difference in the flux magnitude was up to 180 W m −2 . Wendler et al [2005] observed a downward sensible heat flux in the Ross Sea over both broken sea ice (12 W m −2 ) and compact snow‐covered sea ice in the McMurdo Sound (18 W m −2 ). The observation periods of the work of Wendler et al [2005] were, however, short: six days over the broken sea ice and four over the compact sea ice.…”

“… Wendler et al [2005] observed a downward sensible heat flux in the Ross Sea over both broken sea ice (12 W m −2 ) and compact snow‐covered sea ice in the McMurdo Sound (18 W m −2 ). The observation periods of the work of Wendler et al [2005] were, however, short: six days over the broken sea ice and four over the compact sea ice. Hence the synoptic‐scale situation may have had an essential effect on the results.…”

“…They analyzed albedo data from ship‐based field experiments in the East Antarctic sea ice zone, and concluded that a representative albedo of snow‐covered sea ice is 0.87 in September–November and 0.82 in December–February. Also, based on ship data, Wendler et al [2005] observed a mean albedo of 0.81 for compact sea ice cover in late December. Although ship‐based albedo measurements are not as accurate as those made at an ice station, the numbers are very close to our mean value of 0.83 for December.…”

Mesoscale Modeling of the Atmosphere over Antarctic Sea Ice: A Late-Autumn Case Study

“…In situ observations of the atmosphere over this vast area have been rare, restricted to ship observations (mostly summertime; Andreas 1985;Wendler et al 2005), wind and temperature measurements from drifting buoys (Kottmeier and Sellman 1996), and detailed boundary layer observations from two drifting ice stations, in 1992 (Andreas et al 2000(Andreas et al , 2004 and 2004-05 (Bareiss 2008). Data allowing the resolution of mesoscale variations in the atmosphere have been practically absent.…”