A Transient Rise in Tropical Sea Surface Temperature During the Paleocene-Eocene Thermal Maximum

The Paleocene-Eocene Thermal Maximum (PETM) has been attributed to a rapid rise in greenhouse gas levels. If so, warming should have occurred at all latitudes, although amplified toward the poles. Existing records reveal an increase in high-latitude sea surface temperatures (SSTs) (8° to 10°C) and in bottom water temperatures (4° to 5°C). To date, however, the character of the tropical SST response during this event remains unconstrained. Here we address this deficiency by using paired oxygen isotope and minor element (magnesium/calcium) ratios of planktonic foraminifera from a tropical Pacific core to estimate changes in SST. Using mixed-layer foraminifera, we found that the combined proxies imply a 4° to 5°C rise in Pacific SST during the PETM. These results would necessitate a rise in atmospheric pCO2 to levels three to four times as high as those estimated for the late Paleocene.

[1]  G. P. Lohmann,et al.  Incorporation and preservation of Mg in Globigerinoides sacculifer: implications for reconstructing the temperature and 18O/16O of seawater , 2000 .

[2]  J. Erez,et al.  Experimental paleotemperature equation for planktonic foraminifera , 1983 .

[3]  D. Schrag,et al.  Application of benthic foraminiferal Mg/Ca ratios to questions of Cenozoic climate change , 2002 .

[4]  N. Shackleton,et al.  The Paleocene-Eocene benthic foraminiferal extinction and stable isotope anomalies , 1996, Geological Society, London, Special Publications.

[5]  J. Zachos,et al.  Stable isotopic signals and photosymbiosis in Late Paleocene planktic foraminifera , 1994, Paleobiology.

[6]  G. P. Lohmann,et al.  Accurate estimation of sea surface temperatures using dissolution‐corrected calibrations for Mg/Ca paleothermometry , 2002 .

[7]  J. Zachos,et al.  Evolutionary consequences of the latest Paleocene thermal maximum for tropical planktonic foraminifera , 1998 .

[8]  J. Zachos,et al.  Rapid diversification of planktonic foraminifera in the tropical Pacific (ODP Site 865) during the late Paleocene thermal maximum , 1996 .

[9]  J. Zachos,et al.  New evidence for subtropical warming during the Late Paleocene thermal maximum: Stable isotopes from Deep Sea Drilling Project Site 527, Walvis Ridge , 1999 .

[10]  K. Farley,et al.  An alternative age model for the Paleocene–Eocene thermal maximum using extraterrestrial 3He , 2003 .

[11]  J. Zachos,et al.  Warming the fuel for the fire: Evidence for the thermal dissociation of methane hydrate during the Paleocene-Eocene thermal maximum , 2002 .

[12]  M. Keller,et al.  Carbon in Amazon Forests: Unexpected Seasonal Fluxes and Disturbance-Induced Losses , 2003, Science.

[13]  G. Dickens,et al.  A blast of gas in the latest Paleocene: simulating first-order effects of massive dissociation of oceanic methane hydrate. , 1997, Geology.

[14]  G. Schmidt,et al.  Atmospheric composition, radiative forcing, and climate change as a consequence of a massive methane release from gas hydrates , 2003 .

[15]  J. Duplessy,et al.  Carbon and oxygen isotopic composition of planktonic foraminifera from laboratory culture, plankton tows and Recent sediment; implications for the reconstruction of paleoclimatic conditions and of the global carbon cycle , 1985 .

[16]  Jelle Bijma,et al.  Effect of seawater carbonate concentration on foraminiferal carbon and oxygen isotopes , 1997, Nature.

[17]  J. P. Kennett,et al.  Abrupt deep-sea warming, palaeoceanographic changes and benthic extinctions at the end of the Palaeocene , 1991, Nature.

[18]  J. Zachos,et al.  High-resolution records of the late Paleocene thermal maximum and circum-Caribbean volcanism: is there a causal link? , 1997 .

[19]  C. Hemleben,et al.  Assessing the reliability of magnesium in foraminiferal calcite as a proxy for water mass temperatures , 1996 .

[20]  G. Dickens.  Methane oxidation during the late Palaeocene thermal maximum , 2000 .

[21]  Vladimir A Alexeev.  Sensitivity to CO2 doubling of an atmospheric GCM coupled to an oceanic mixed layer: a linear analysis , 2003 .

[22]  J. Kennett,et al.  Antarctic subtropical humid episode at the Paleocene-Eocene boundary: Clay-mineral evidence , 1994 .

[23]  D. Beerling,et al.  Paleobotanical evidence for near present-day levels of atmospheric Co2 during part of the tertiary. , 2001, Science.

[24]  R. Zeebe.  Seawater pH and isotopic paleotemperatures of Cretaceous oceans , 2001 .

[25]  L. Sloan,et al.  Climate model sensitivity to atmospheric CO2 levels in the Early–Middle Paleogene , 2003 .

[26]  Henry Elderfield,et al.  Calibration of Mg/Ca thermometry in planktonic foraminifera from a sediment trap time series , 2003 .

[27]  G. Wefer,et al.  New chronology for the late Paleocene thermal maximum and its environmental implications , 2000 .

[28]  J. Ashby.  References and Notes , 1999 .

[29]  L. Sloan,et al.  Trends, Rhythms, and Aberrations in Global Climate 65 Ma to Present , 2001, Science.

[30]  B. Schmitz,et al.  Global dinoflagellate event associated with the late Paleocene thermal maximum , 2001 .

[31]  R. M. Owen,et al.  Dissociation of oceanic methane hydrate as a cause of the carbon isotope excursion at the end of the Paleocene , 1995 .

[32]  J. Zachos,et al.  Evolution of Early Cenozoic marine temperatures , 1994 .