Glacial-interglacial dynamics of the eastern equatorial Pacific cold tongue Intertropical Convergence Zone system reconstructed from oxygen isotope records

LDEO Publication: 
Publication Type  Journal Article
Year of Publication  2003
Authors  Koutavas, A.; Lynch-Stieglitz, J.
Journal Title  Paleoceanography
Volume  18
Issue  4
Pages  -
Journal Date  Dec 4
ISBN Number  0883-8305
Accession Number  ISI:000187486200001
LDEO Publication Number  6653
Key Words  cold tongue; itcz; oxygen isotopes; tropical pacific; sea-surface temperature; ocean-atmosphere system; tropical pacific; planktonic-foraminifera; panama basin; ice-age; climate-change; globigerinoides-sacculifer; el-nino; millennial timescales

We use planktonic oxygen isotope (delta(18)O) records spanning the last 30,000 years (kyr) to constrain the magnitude and spatial pattern of glacial cooling in the upwelling environment of the eastern equatorial Pacific (EEP). Fourteen new downcore delta(18)O records were obtained from surface-dwelling planktonic foraminifera Globigerinoides sacculifer and Globigerinoides ruber in eight cores from the upwelling tongue of the EEP. All sites have sedimentation rates exceeding 5 cm/kyr and, with one exception, lie above the modern depth of the foraminiferal lysocline. Sites directly underlying the cool band of upwelling immediately south of the equator record mean late Holocene (LH)-Last Glacial Maximum (LGM) delta(18)O amplitudes ranging between 1.0 and 1.3parts per thousand. We estimate that mean sea surface temperatures (SST) in this region during the LGM were on average 1.5 +/- 0.5degreesC lower than the LH. Larger delta(18)O amplitudes are observed in sites north of the equator, indicating a spatial pattern of reduced meridional SST gradient across the equator during the LGM. This result is supported by comparison of Mg/Ca SST reconstructions from two sites straddling the equator. We interpret the reduction of this gradient during the LGM as evidence for a less intense cold tongue-Intertropical Convergence Zone (ITCZ) frontal system, a more southerly position of the ITCZ, and weaker southeast equatorial trades in the EEP.


756NFTimes Cited:13Cited References Count:100

URL  <Go to ISI>://000187486200001
DOI  Doi 10.1029/2003pa000894