Impact of sea-ice formation on the properties of Antarctic bottom water

Abstract

ABSTRACT. [ t is ge nerally accepted th a t fresh-wa ter flu xes du e to ice accre ti o n or melting p rofo undl y influence the formati o n o f An tarctic bottom water (AA B\V ). Thi s is investigated by means of a globa l, three-dim ensiona l ice ocea n model. Two model runs were co nducted. At th e hi gh so uth ern latitudes, the co ntrol ex periment ex hibits positive (i. e. toward s the ocean ) fr esh-water flu xes over the deep ocea n, a nd la rge negative fluxes over th e Anta rctic contin ental shelf, because of the intense ice-production ta king place in this region. Th e salinity of shelf water can increase in such a way th at deep-water form ati on is facilitated. Th e simulated net fresh-water flu x ove r the shelf has a n a nnual mean va lue of -1 m a I. T hi s flu x induces a transport of salt to bottom wa ters, which corres po nd s to a n increase o[their salinity es tim a ted to be a round 0.05 psu. In th e seco nd m odel run, the fresh-water Duxes due to ice melting or freez ing a re neglected, leading to a rearrangement of the water m asses. In particul a r, the AABW-form ation rate decreases, which all ows th e influence of North Atl antic deep water (NADW ) to increase. As NADW is warm er a nd saltier th an AABW, th e bottom-water sa lini ty a nd temperature become higher.

Desalination processes of sea ice revisited

“…Properly understanding the strength and intermittency of this salt flux might prove crucial to understanding the World's ocean circulation and its development under future climate conditions when there may possibly be a substantially reduced sea‐ice cover but a greater seasonal variation. For example, numerical studies indicate that the formation rate of Antarctic Bottom Water is highly dependent on the amount of salt that is lost from sea ice [ Goosse et al , 1997; Stössel et al , 2002]. In the Arctic, the salt loss from sea ice during its formation is thought to contribute to maintaining the Arctic Halocline and gives rise to a variety of local water mass transformations [ Aagaard et al , 1981; Skogseth et al , 2005; Stott , 2005].…”

Importance of ice‐ocean interactions for the global ocean circulation: A model study

“…Contrary to the heat and momentum fluxes at the ice-ocean interface, the influence of salt/freshwater exchange between ice and ocean has been studied before with global ocean models [e.g., Toggweiler and Samuels, 1995a;England and Hirst, 1997] or global coupled ice-ocean models [e.g., Legutke et al, 1997;Goosse et al, 1997b;StOssel et al, 1998]. Taking into account the impact of sea ice on the freshwater/salt flux in ocean-only models is problematic, and the way it was done in the past could profoundly affect the results.…”

North Atlantic Deep Water and Antarctic Bottom Water: Their interaction and influence on the variability of the global ocean circulation

“…The climatic consequence was depicted as a bipolar seesaw with stronger heat release from the Southern Ocean and warming in Antarctica during periods of strong deep water formation in the Southern Hemisphere accompanied by weak heat release and cooling in the North and vice versa. Cox [1989] analyzing four idealized global ocean experiments, Goosse et al [1997] varying freshwater fluxes and Fieg [1996] and Fieg and Gerdes [2001], comparing the results of over twenty numerical experiments with both LGM (Last Glacial Maximum) and recent boundary conditions, find a similar seesawing behavior in the strength of NADW and AABW.…”