TY - JOUR
T1 - Circulation and variability in the Chile Basin
AU - Shaffer, Gary
AU - Hormazabal, Samuel
AU - Pizarro, Oscar
AU - Ramos, Marcel
N1 - Funding Information:
We thank those involved in the extensive deep sea mooring work upon which much of our results are based. These include the captains and crews of R.V. Abate Molina, R.V. Vidal Gormaz and R.V. Sonne, Per-Ingvar Sehlstedt and Henning Hundahl (University of Copenhagen), Dierk Hebbeln (University of Bremen), Sergio Salinas (Catholic University of Valparaiso) and Caesar Hormazabal and Luis Bravo (University of Concepcion). Sea surface height anomalies from combined processing of ERS 1,2 and TOPEX/POSEIDON satellite data were obtained from AVISO ( http://www.jason.oceanobs.com ). ERS and QuikSCAT satellite scatterometer wind stress data were obtained from Département d’Océanographie Spatiale, IFREMER, France ( www.ifremer.fr/droos ) and the Jet Propulsion Laboratory ( http://podaac.jpl.nasa.gov/quikscat ), respectively. World Ocean Circulation Experiment P6 line data were obtained from the WOCE Hydrographic Program Office ( http://whpo.ucsd.edu/whp_data.htm ) and from the Joint Archive for Shipboard ADCP at the University of Hawaii ( ftp://ilikai.soest.hawaii.edu ). This research was supported by grants and scholarships from the Swedish Agency for Research Cooperation with Developing Countries, from the National Research Councils of Denmark, Sweden and Chile (FONDAP- Humboldt Current program, the FONDAP-COPAS center and FONDECYT grant nr.1020294), from Fundacion Andes, and from the Danish National Research Foundation.
PY - 2004/10
Y1 - 2004/10
N2 - Current observations at several depths between 250 and 3750m are reported from a 30°S, deep sea site 150km off the Chile coast for the period July 1993-June 2001. These results are used with current observations from a nearby slope site, satellite altimeter data, and hydrographic and Acoustic Doppler Current Profiler data from the WOCE P6E section along 32.5°S to address mean and variable flow in the Chile Basin. Strong current variability in the upper ocean for periods more than 100 days is explained in terms of remotely forced Rossby waves, local baroclinic instabilities of coastal currents and variable wind forcing. Intraseasonal to seasonal current variability at the deep ocean site was greatest during La Niña events while intraseasonal variability at the slope site was greatest during the 1997-1998 El Niño event. Mean westward and poleward flow was observed at all depths at the deep sea site but upper ocean means were not significantly different from zero. There was a well-defined, mean poleward flow of 0.6±0.3cms-1 at 2450m depth there. Geostrophic current calculations are presented for the P6E section with levels of no motion based on our current observations and other constraints. These reference choices yield reasonable and consistent results for the steady-state heat balance of the deep Chile and Peru Basins. Results show a deep equatorward flow of 3-4Sv on the eastern flank of the East Pacific Rise and a deep poleward boundary flow of about 10Sv within 1500km of the Chile coast. Up to half of the total mid-depth outflow of the South Pacific may take place east of the Rise. Thus the deep poleward boundary current off Chile is a major component of the deep circulation of the global ocean but the dynamics of this current remain a puzzle.
AB - Current observations at several depths between 250 and 3750m are reported from a 30°S, deep sea site 150km off the Chile coast for the period July 1993-June 2001. These results are used with current observations from a nearby slope site, satellite altimeter data, and hydrographic and Acoustic Doppler Current Profiler data from the WOCE P6E section along 32.5°S to address mean and variable flow in the Chile Basin. Strong current variability in the upper ocean for periods more than 100 days is explained in terms of remotely forced Rossby waves, local baroclinic instabilities of coastal currents and variable wind forcing. Intraseasonal to seasonal current variability at the deep ocean site was greatest during La Niña events while intraseasonal variability at the slope site was greatest during the 1997-1998 El Niño event. Mean westward and poleward flow was observed at all depths at the deep sea site but upper ocean means were not significantly different from zero. There was a well-defined, mean poleward flow of 0.6±0.3cms-1 at 2450m depth there. Geostrophic current calculations are presented for the P6E section with levels of no motion based on our current observations and other constraints. These reference choices yield reasonable and consistent results for the steady-state heat balance of the deep Chile and Peru Basins. Results show a deep equatorward flow of 3-4Sv on the eastern flank of the East Pacific Rise and a deep poleward boundary flow of about 10Sv within 1500km of the Chile coast. Up to half of the total mid-depth outflow of the South Pacific may take place east of the Rise. Thus the deep poleward boundary current off Chile is a major component of the deep circulation of the global ocean but the dynamics of this current remain a puzzle.
KW - Abyssal circulation
KW - Chile Basin
KW - Current measurement
KW - Deep currents
KW - Eastern South Pacific Ocean
KW - Eastern boundary currents
UR - http://www.scopus.com/inward/record.url?scp=4143081357&partnerID=8YFLogxK
U2 - 10.1016/j.dsr.2004.05.006
DO - 10.1016/j.dsr.2004.05.006
M3 - Article
AN - SCOPUS:4143081357
VL - 51
SP - 1367
EP - 1386
JO - Deep-Sea Research Part I: Oceanographic Research Papers
JF - Deep-Sea Research Part I: Oceanographic Research Papers
SN - 0967-0637
IS - 10
ER -