Climatic effects of reduced Arctic sea ice limits in the Giss II General Circulation Model

Abstract

In this paper we present results of an atmospheric general circulation model (GCM) experiment in which Arctic sea ice limits were substantially reduced in all months. March sea ice limits were set equivalent to modem September limits, and all sea ice was removed in September. Sea ice coverage for other months varied between these two extremes. This climate sensitivity experiment makes predictions about mean northern hemisphere atmospheric conditions (including temperature, pressure, wind patterns, and precipitation) consistent with these boundary constraints. The major effects of reduced sea ice limits are observed in winter. They include large regional warming of the circum-Arctic region, northward migration of the Icelandic low pressure system, and strengthening of the Azores high. Changes in net heating over the North Atlantic Ocean suggest that increases in sea surface temperatures and salinities in this region would also accompany reductions in Arctic sea ice limits. In the wind field, a weakening of the polar easteries and an intensification of cyclonic circulation over the Norwegian-Greenland Sea suggest that surface water exchange between the Atlantic and Arctic would increase when sea ice limits are reduced. However, zonally averaged changes in strength of the westerlies or upper level jet stream are minimal. The late Pliocene cooling of the North Atlantic Ocean and North American Arctic margin may have been linked in part to the development of perennial sea ice cover.

Deep-water circulation, chemistry, and terrigenous sediment supply in the equatorial Atlantic during the Pliocene, 3.3–2.6 Ma and 5–4.5 Ma

“…General circulation model experiments that examined the warmer Pliocene climate prior to the intensification of northern hemisphere glaciation suggested a strengthening of the thermohaline circulation as a result of a salinity increase in the source area of NADW production (Raymo et al, 1990a;Chandler et al, 1994). The prediction of enhanced thermohaline circulation in the North Atlantic during the warmer period of the Pliocene is not reflected by our results.…”

An interannual link between Arctic sea-ice cover and the North Atlantic Oscillation

“…However, controversy exists regarding the amplitude and robustness of the signal (Screen 2014;Barnes 2013). Previously, mass adjustment at high latitudes under the removal of sea ice cover and associated mid-latitudes cooling, was shown (Royer et al 1990;Raymo et al 1990) to affect particularly the wave-number four pattern. This adjustment showed mid-tropospheric geopotential height increases over the Atlantic (Iceland and Norwegian Sea) and the Eurasian (Siberia and West Bering Sea) sectors and decreases over the East Pacific, Sea of Japan, Black Sea and West Atlantic areas.…”

The Mid‐Pleistocene climate transition: A deep sea carbon isotopic perspective

“…One possibility is that sea ice limits were expanded; such a change would result in pronounced regional cooling in winter (influencing NADW production) but cause no change in summer surface temperatures (the season controlling continental ice mass balance) [Raymo et al, 1990b]. Future studies should look for similar long-term trends in both the position of the North Atlantic ice-rafted debris belt and atmospheric pCO 2.…”