Chapter 20
Studies of Water Masses Mixing in the Ross Sea
(Antarctica) Using Chemical Tracers
P. Rivaro . R. Frache
20.1
Introduction
Recent oceanographic observations near the Antarctic continent renewed interest
about the role of the high latitudes in climatic changes. In fact, the production of dense
waters in the ocean at polar regions has a significant effect on the global deep ocean
circulation (Whitworth et al. 1998). These water masses, which have relatively high
concentrations of oxygen acquired from the atmosphere, flow away from Antarctic
regions and sink. introducing water with near-surface characteristics into deep ocean.
This process, called ventilation, is associated with important fluxes of heat, salt, nutrients and gases.
The Antarctic Ross Sea (Fig. 20.1) is an interesting area, where different important
aspects such as ice melting, water mass formation, mixing, and spreading can be observed and studied.
The Ross Sea is a wide continental shelf, with an area of about 500 000 km 2 , bounded
west by the Victoria Land coast and east by Edward VII Land; the northern boundary
can be considered the line from Cape Adare to Cape Colbeck, and the southern boundary is the Ross Ice Shelf (RIS). The RIS extends over nearly half the continental shelf
and is about 250 m thick on its northernmost side (Jacobs 1989). The Ross Ice Shelf
limits only the uppermost waters, while the deeper waters can circulate freely under
the ice shelf (Budillon et al.1999).
The topography of the continental shelf is locally modified by canyons and banks,
and the mean depth is about 450 m (Picco et al. 1999).
The characteristics of the water masses of the Ross Sea have been described by several authors (Jacobs et al. 1985; Locarnini 1994).
The available evidence indicates that most of the dense deep-water production in
high southern latitudes originates on the continental shelf and onto the continental
slope, mixing with ambient water. If this mixed fluid becomes equal to the ambient
density of the ocean at a given level, it will leave the vicinity of the continental slope
and settle at this particular level.
If instead it reaches the bottom of the slope, it may become Antarctic Bottom Water (AABW) (Baines and Condie 1998).
Many of the details of the processes of dense water formation on the continental
shelf and its flow down the slope are still obscure, and these details probably vary from
location to location.
Dense waters are primarily formed on the Antarctic continental shelf by the formation of sea ice in autumn and winter with the consequent rejection of brine, which
produces salty water at ~ -1.85 °C potential temperature at the freezing point. This pro-
Studies of Water Masses Mixing in the Ross Sea
(Antarctica) Using Chemical Tracers
P. Rivaro . R. Frache
20.1
Introduction
Recent oceanographic observations near the Antarctic continent renewed interest
about the role of the high latitudes in climatic changes. In fact, the production of dense
waters in the ocean at polar regions has a significant effect on the global deep ocean
circulation (Whitworth et al. 1998). These water masses, which have relatively high
concentrations of oxygen acquired from the atmosphere, flow away from Antarctic
regions and sink. introducing water with near-surface characteristics into deep ocean.
This process, called ventilation, is associated with important fluxes of heat, salt, nutrients and gases.
The Antarctic Ross Sea (Fig. 20.1) is an interesting area, where different important
aspects such as ice melting, water mass formation, mixing, and spreading can be observed and studied.
The Ross Sea is a wide continental shelf, with an area of about 500 000 km 2 , bounded
west by the Victoria Land coast and east by Edward VII Land; the northern boundary
can be considered the line from Cape Adare to Cape Colbeck, and the southern boundary is the Ross Ice Shelf (RIS). The RIS extends over nearly half the continental shelf
and is about 250 m thick on its northernmost side (Jacobs 1989). The Ross Ice Shelf
limits only the uppermost waters, while the deeper waters can circulate freely under
the ice shelf (Budillon et al.1999).
The topography of the continental shelf is locally modified by canyons and banks,
and the mean depth is about 450 m (Picco et al. 1999).
The characteristics of the water masses of the Ross Sea have been described by several authors (Jacobs et al. 1985; Locarnini 1994).
The available evidence indicates that most of the dense deep-water production in
high southern latitudes originates on the continental shelf and onto the continental
slope, mixing with ambient water. If this mixed fluid becomes equal to the ambient
density of the ocean at a given level, it will leave the vicinity of the continental slope
and settle at this particular level.
If instead it reaches the bottom of the slope, it may become Antarctic Bottom Water (AABW) (Baines and Condie 1998).
Many of the details of the processes of dense water formation on the continental
shelf and its flow down the slope are still obscure, and these details probably vary from
location to location.
Dense waters are primarily formed on the Antarctic continental shelf by the formation of sea ice in autumn and winter with the consequent rejection of brine, which
produces salty water at ~ -1.85 °C potential temperature at the freezing point. This pro-