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The interior circulation of the world's oceans is known to play a major role in the distribution of the
planet's heat. If we want to understand climate and its changes we therefore also need to understand the long-
and short-term processes in the ocean, including the ocean conveyor belt. Its heat transport carries the same order
of magnitude of energy away from the tropics towards the poles as the atmosphere, making a
substantial contribution to the moderate climate of maritime and continental Europe.
Because of its fundamental role in climate control, intensive research in recent years has been aimed at understanding the different mechanisms involved in the ocean conveyor belt, to calculate transports of water masses along its path through the oceans. Recent studies emphasized the strong connection of the northern and southern polar regions, and showed that it operates through changes in ocean circulation. In particular, if we want to understand the general circulation, we have to understand all the processes involved in it, including the transport and modifications of heat and salt within the Antarctic Circumpolar Current (ACC) around the globe.
With increasing expectations for predictions at increasingly fine resolutions, models must become more
sophisticated, and the need for detailed in-situ observations is growing quickly and has never been more
acute. Data are needed from regions and seasons where traditional hydrographic data (e.g. ship-based
CTDs, Argo floats etc.) are scarce and/or difficult and expensive to implement. New approaches are being
developed to fill this gap.
One such new approach to gather oceanographic data was demonstrated by the international SEaOS program. During 2004 to 2006, ~85 state-of-the-art animal-borne CTD tags were deployed on southern elephant seals (Mirounga leonina) in late summer at key breeding and moulting sites around the Southern Ocean: South Georgia, Kerguelen, Macquarie Island and the South Shetland Islands.
Seal migrations covered all
longitudinal sectors of the Southern Ocean as well as its entire latitudinal range, from the Subtropical Front in
the north via the ACC to polar continental waters along the Antarctic coast, where many seals spent substantial
amounts of time within the winter pack ice in areas difficult or impossible to sample using other means.
SEaOS has provided over 21,000 CTD profiles at a rate of ~2 profiles/day, representing a combination
of transect-type sections with a spatial resolution of less than 25km along the migratory routes of the seals, and
detailed longitudinal mooring-like data from concentrated feeding areas. This dataset has greatly
increased the coverage in regions where historical hydrographic data are available and where Argo floats
have been sampling intensively over the past years. But the greatest contribution of these new sampling
platforms is the substantial increase in the number of CTD profiles from areas that have previously been virtually un-sampled,
especially below 60ºS and during the winter months. During its three years of operation
SEaOS provided more than three times the total number historical profiles previously available from
these latitudes.