Monitoring Drake Passage with elephant seals: Frontal structures and snapshots of transport

Conductivity–temperature–pressure satellite relay data loggers (CTD-SRDLs) were attached to southern elephant seals (Mirounga leonina) on the island of South Georgia. During the animals’ migration the CTDSRDLs recorded and transmitted hydrographic profiles at a rate of approximately two profiles per day to an average depth of about 547 m, representing transect-type sections with a spatial resolution of 16–47 km along the migratory routes of the seals. Two sections are used to clearly identify the locations of the Antarctic Circumpolar Current fronts across Drake Passage, providing in situ data complementary to satellite and other techniques. An empirical relationship between upper ocean temperature and baroclinic mass transport is used to determine the transport through Drake Passage at the times of the sections, and these transports are compared with estimates derived by other techniques. An absolute geostrophic velocity section across Drake Passage is calculated using CTD-SRDL data and data of absolute geostrophic surface velocities from altimetry. The mean total baroclinic transports in June 2004 and April 2005 are estimated to be 124 3 106 6 14 3 106 m3 s21 and 112 3 106 6 14 3 106 m3 s21 respectively.

[1]  S. Sokolov,et al.  Structure of Southern Ocean fronts at 140°E , 2002 .

[2]  James G. Richman,et al.  Location and dynamics of the Antarctic Polar Front from satellite sea surface temperature data , 1999 .

[3]  A. Orsi,et al.  On the meridional extent and fronts of the Antarctic Circumpolar Current , 1995 .

[4]  J. Sprintall.  Seasonal to interannual upper-ocean variability in the Drake Passage , 2003 .

[5]  Michael P. Meredith,et al.  Circumpolar response of Southern Ocean eddy activity to a change in the Southern Annular Mode , 2006 .

[6]  M. Meredith,et al.  On the sampling timescale required to reliably monitor interannual variability in the Antarctic circumpolar transport , 2005 .

[7]  J. Allen,et al.  On the physical structure of a front in the Bellingshausen Sea , 1995 .

[8]  David W. J. Thompson,et al.  Interpretation of Recent Southern Hemisphere Climate Change , 2002, Science.

[9]  F. Hernandez,et al.  A mean dynamic topography computed over the world ocean from altimetry, in situ measurements, and a geoid model , 2004 .

[10]  S. Sokolov,et al.  Upper ocean temperature and the baroclinic transport stream function relationship in Drake Passage , 2004 .

[11]  Wolfgang H Berger,et al.  The South Atlantic: Present and Past Circulation , 1996 .

[12]  J. Church,et al.  Ocean Circulation and Climate: Observing and Modelling the Global Ocean , 2001 .

[13]  M. Biuw,et al.  The ACC frontal system in the South Atlantic: Monitoring using merged Argo and animal-borne sensor data , 2008 .

[14]  A. Gordon,et al.  Intermediate waters in the southwest South Atlantic , 1989 .

[15]  J. Sprintall,et al.  Mean jets, mesoscale variability and eddy momentum fluxes in the surface layer of the Antarctic Circumpolar Current in Drake Passage , 2007 .

[16]  Janet Sprintall,et al.  Location of the Antarctic Polar Front from AMSR-E Satellite Sea Surface Temperature Measurements , 2006 .

[17]  Dirk Olbers,et al.  The Antarctic Circumpolar Current System , 1999 .

[18]  S. Rintoul,et al.  Seasonal evolution of upper ocean thermal structure between Tasmania and Antarctica , 1997 .

[19]  J. Wallace,et al.  Annular Modes in the Extratropical Circulation. Part I: Month-to-Month Variability* , 2000 .

[20]  M. A. Fedak,et al.  Variations in behavior and condition of a Southern Ocean top predator in relation to in situ oceanographic conditions , 2007, Proceedings of the National Academy of Sciences.

[21]  Bernie J. McConnell,et al.  Salinity and temperature structure of a freezing Arctic fjord—monitored by white whales (Delphinapterus leucas) , 2002 .

[22]  Worth D. Nowlin,et al.  Structure and Transport of the Antarctic Circumpolar Current at Drake Passage from Short-Term Measurements , 1977 .

[23]  E. Murphy,et al.  Southern ACC Front to the northeast of South Georgia: Pathways, characteristics, and fluxes , 2003 .

[24]  R. Peterson,et al.  Volume Transport of the Antarctic Circumpolar Current from Bottom Pressure Measurements , 1985 .

[25]  Sarah T. Gille,et al.  Aliasing of high‐frequency variability by altimetry: Evaluation from bottom pressure recorders , 2001 .

[26]  J. Klinck,et al.  The physics of the Antarctic Circumpolar Current , 1986 .

[27]  W. Nowlin,et al.  Transport of water through the Drake Passage , 1971 .

[28]  J. S. Godfrey,et al.  Mass and heat budgets in the East Australian current: A direct approach , 1994 .

[29]  Sarah T. Gille,et al.  Ocean Circulation and Climate—Observing and Modelling the Global Ocean , 2001 .

[30]  Seasonal to interannual variability from expendable bathythermograph and TOPEX/Poseidon altimeter data in the South Pacific subtropical gyre , 2000 .

[31]  A. Gordon,et al.  Southern Ocean fronts from the Greenwich Meridian to Tasmania , 1996 .

[32]  T. Whitworth.  Monitoring the Transport of the Antarctic Circumpolar Current at Drake Passage , 1983 .

[33]  Robert S. Linzell,et al.  The Temperature and Depth Accuracy of Sippican T-5 XBTs , 1993 .

[34]  M. Meredith,et al.  Coherence of Antarctic sea levels, Southern Hemisphere Annular Mode, and flow through Drake Passage , 2003 .

[35]  M. Brandon,et al.  Transport and variability of the Antarctic Circumpolar Current in Drake Passage , 2003 .

[36]  M. Meredith,et al.  Changes in the ocean transport through Drake Passage during the 1980s and 1990s, forced by changes in the Southern Annular Mode , 2004 .

[37]  M. Meredith,et al.  Distribution of oxygen isotopes in the water masses of Drake Passage and the South Atlantic , 1999 .