Eastern Equatorial Pacific Early Pliocene Mg/Ca Subsurface Temperature Ford, H.L.; Ravelo, A.C.; Hovan, S. Ford, H.L. Ravelo, A.C. Hovan, S. Sea Surface Temperature Reconstruction thermal maximum earth science/paleoclimate/paleoceanography (delta 13C,Globorotalia tumida,null,per mil PDB,null,paleoceanography,null,null,N,null) earth science/paleoclimate/paleoceanography (depth,null,null,meter,null,paleoceanography,null,null,N,null) earth science/paleoclimate/climate reconstructions|paleoceanography (sea water temperature,magnesium/calcium,null,degree Celsius,null,climate reconstructions|paleoceanography,null,null,N,based on Globorotalia tumida (depth habitat ~50-100m)) earth science/paleoclimate/paleoceanography (age,null,null,million years ago,null,paleoceanography,null,null,N,null) earth science/paleoclimate/paleoceanography (magnesium/calcium,Globorotalia tumida,null,dimensionless,null,paleoceanography,null,null,N,null) earth science/paleoclimate/paleoceanography (notes,null,null,null,null,paleoceanography,null,null,C,Site Hole Core Type Section Interval-cm) earth science/paleoclimate/paleoceanography (delta 18O,Globorotalia tumida,null,per mil PDB,null,paleoceanography,null,null,N,null) earth science/paleoclimate/paleocean earth science/paleoclimate/paleocean earth science/paleoclimate/paleocean earth science/paleoclimate/paleocean (ODP 849>LATITUDE .18>LONGITUDE -110.52) (ODP 848B>LATITUDE -2.98>LONGITUDE -110.47) (ODP 853B>LATITUDE 7.2>LONGITUDE -109.75) During the early Pliocene warm period (~4.6-4.2 Ma) in the Eastern Equatorial Pacific upwelling region, sea surface temperatures were warm in comparison to modern conditions. Warm upwelling regions have global effects on the heat budget and atmospheric circulation, and are argued to have contributed to Pliocene warmth. Though warm upwelling regions could be explained by weak winds and/or a deep thermocline, the temporal and spatial evolution of the equatorial thermocline is poorly understood. Here we reconstruct temporal and spatial changes in subsurface temperature to monitor thermocline depth and show the thermocline was deeper during the early Pliocene warm period than it is today. We measured subsurface temperature records from Eastern Equatorial Pacific ODP transect Sites 848, 849, and 853 using Mg/Ca records from Globorotalia tumida, which has a depth habitat of ~50-100 m. In the early Pliocene, subsurface temperatures were ~4-5°C warmer than modern temperatures, indicating the thermocline was relatively deep. Subsurface temperatures steeply cooled ~2-3°C from 4.8 to 4.0 Ma and continued to cool an additional 2-3°C from 4.0 Ma to present. Compared to records from other regions, the data suggests the pronounced subsurface cooling between 4.8 and 4.0 Ma was a regional signal related to restriction of the Isthmus of Panama, while continued cooling from 4.0 Ma to present was likely related to global processes that changed global thermocline structure. Additionally, the spatial evolution of the equatorial thermocline along a N-S transect across ODP Sites 853, 849 and 848 suggests an intensification of the southeast trades from the Pliocene to present. Large-scale atmospheric and oceanographic circulation processes link high and low latitude climate through their influence on equatorial thermocline source water regions and consequently the equatorial thermocline. Through these low latitude/high latitude linkages, changes in the equatorial thermocline and thermocline source water played an important role in the transition from the warm Pliocene to the cold Pleistocene. STUDY NOTES: Mg/Ca paleothermometry from the planktonic foraminifera Globorotalia tumida from the past ~5 Ma at Ocean Drilling Program (ODP) Site 848 in the eastern equatorial Pacific NCDC-Paleoclimatology https://www.ncdc.noaa.gov/data-access/paleoclimatology-data - Bauer Bruce Investigator : Ford, H.L. Investigator : Ravelo, A.C. Investigator : Hovan, S. 2012-11-13 ONLINE Files online, ASCII https://www.ncdc.noaa.gov/paleo/study/13538 https://www1.ncdc.noaa.gov/pub/data/paleo/contributions_by_author/ford2012/ford2012odp848.txt https://www1.ncdc.noaa.gov/pub/data/paleo/contributions_by_author/ford2012/ford2012odp853.txt https://www1.ncdc.noaa.gov/pub/data/paleo/contributions_by_author/ford2012/ford2012odp849.txt https://www1.ncdc.noaa.gov/pub/data/paleo/contributions_by_author/ford2012/ford2012odp848.txt https://www1.ncdc.noaa.gov/pub/data/paleo/contributions_by_author/ford2012/ford2012odp853.txt https://www1.ncdc.noaa.gov/pub/data/paleo/contributions_by_author/ford2012/ford2012odp849.txt English https://www.ncdc.noaa.gov/paleo/study/13538 https://www1.ncdc.noaa.gov/pub/data/paleo/contributions_by_author/ford2012/ford2012odp848.txt https://www1.ncdc.noaa.gov/pub/data/paleo/contributions_by_author/ford2012/ford2012odp853.txt https://www1.ncdc.noaa.gov/pub/data/paleo/contributions_by_author/ford2012/ford2012odp849.txt Ford, H.L., Ravelo, A.C., and Hovan, S. 2012. A deep Eastern Equatorial Pacific thermocline during the early Pliocene warm period. Earth and Planetary Science Letters, Vol. 355-356, pp. 152-161. DOI: 10.1016/j.epsl.2012.08.027 START YEAR: 5880000 cal yr BP * END YEAR: 0 cal yr BP -110.52 -2.98 -109.75 7.2