OceanObs’09
Community White Paper Proposal
Title
Session 2B: Animal-borne sensors reveal new ocean
processes in polar regions
Lead author
Jean-Benoit Charrassin, LOCEAN, Département Milieux et Peuplements Aquatiques,
Muséum National d'Histoire Naturelle, 43 rue Cuvier, 75231 Paris Cedex 05, France,,
jbc@mnhn.fr
Contributing authors
Keith Nicholls, British Antarctic Survey, NERC, High Cross, Madingley Road,
Cambridge, CB3 0ET, UK
Fabien Roquet, , LOCEAN, Département Milieux et Peuplements Aquatiques,
Muséum National d'Histoire Naturelle, 43 rue Cuvier, 75231 Paris Cedex 05, France
Young-Hyang Park, , LOCEAN, Département Milieux et Peuplements Aquatiques,
Muséum National d'Histoire Naturelle, 43 rue Cuvier, 75231 Paris Cedex 05, France
Lars Boehme, NERC Sea Mammal Research Unit, University of St Andrews, St
Andrews, KY16 8LB, UK, lb284@st-andrews.ac.uk
Christophe Guinet, Centre d'Etudes Biologiques de Chizé - CNRS UPR 1934, Villiers
en Bois, F-79360 Beauvoir sur Niort, France
Mike Meredith, British Antarctic Survey, NERC, High Cross, Madingley Road,
Cambridge, CB3 0ET, UK, mmm@bas.ac.uk
Steve Rintoul, CSIRO, Hobart, Tasmania, Australia
S. Sokolov, CSIRO, Hobart, Tasmania, Australia
Daniel P. Costa, Center for Ocean Health, 100 Shaffer Road, University of California,
Santa Cruz, CA 95060, USA, costa@biology.ucsc.edu, + 1 831 459 2786
Description
Polar regions are particularly sensitive to climate change and changes within them
have important effects elsewhere. There is potential for significant feedback
between ocean circulation, sea ice, and the ocean carbon cycle. However, the
difficulty in obtaining in situ data means that our ability to detect and interpret
changes is very limited, especially in the Polar Oceans, where the water column
structure beneath the sea ice remains almost entirely unobserved and the rate of
sea-ice formation is poorly known. Here, we show that animal-borne CTD sensors
can measure ocean structure and water mass changes in regions and seasons rarely
observed with traditional oceanographic platforms. In particular, southern elephant
seals provided a 30-fold increase in hydrographic profiles from the sea-ice zone,
allowing the major fronts to be mapped south of 60°S and sea-ice formation rates to
be inferred from changes in upper ocean salinity. Oceanographic data obtained by
southern elephant seals also revealed the monthly variability of the Antarctic
Curcumpolar Current in the South Atlantic and were used to investigate the
transports through Drake Passage. Weddell Seals tagged with a miniaturized
conductivity-temperature-depth (CTD) instruments travelled over the central southern
Weddell Sea continental shelf in the winter time and yielded 750 CTD profiles, 250 of
them to the sea floor. The data show a full depth flow of water onto the shelf via a sill
at the shelf break (74°S 44°W). The warmth from the core of the flow was able to
maintain the surface mixed layer above the freezing point, resulting in a band of
reduced ice-production. An estimate of the on-shelf flux suggests that this flow
accounts for most of the estimated 3 Sv of water draining from the southern Weddell
Sea continental shelf.
By providing measurements from the high-latitude ocean during winter, ocean
profilers carried by seals fill a important “blind spot” in our sampling coverage,
enabling the establishment of a truly global ocean-observing system.