Makassar Strait 2000 Year Foraminiferal Mg/Ca and Stable Isotope Data Newton, A.; Thunell, R.C.; Stott, L.D. Newton, A. Thunell, R.C. Stott, L.D. Little Ice Age (LIA) Medieval Warm Period earth science/paleoclimate/paleoceanography (magnesium/calcium,Globigerinoides ruber,null,dimensionless,null,paleoceanography,null,inductively-coupled plasma atomic emission spectroscopy,N,null) earth science/paleoclimate/paleoceanography (depth,null,null,centimeter,null,paleoceanography,null,null,N,null) earth science/paleoclimate/paleoceanography (delta 18O,Globigerinoides ruber,null,per mil VPDB,null,paleoceanography,null,isotope ratio mass spectrometry,N,null) earth science/paleoclimate/paleocean earth science/paleoclimate/paleocean (MD98-2160>LATITUDE -5.2>LONGITUDE 117.48) (MD98-2177>LATITUDE 1.4033>LONGITUDE 119.078) The Indonesian Throughflow (ITF) is the only low-latitude conduit for exchange of surface and thermocline waters between the Indian and Pacific Oceans; 80% of the ITF waters pass through the Makassar Strait. The flux of heat and salt through the strait is, in part, a function of the density difference between its southern and northern ends. Here the Mg/Ca and stable oxygen isotope compositions of the planktonic foraminifer Globigerinoides ruber sampled from two sediment cores collected at the northern and southern ends of the Makassar Strait are used to reconstruct surface-water temperature (SST), sea-surface salinity (SSS), and seawater density variability over the past 2000 yr. Maximum SST and SSS occurred at both sites between 850 and 700 yr ago, coinciding with the Medieval Solar Maximum and Medieval Warm Period (ca. 1000-700 yr ago). SST and SSS declined at both locations after 700 yr ago and reached minimum values during the Little Ice Age, between 300 and 100 yr ago. However, the magnitude of SST and SSS change over the past 2000 yr was distinctly different between the two sites, especially during the period between 2000 and 900 yr ago. This led to changes in the south to north density gradient within the Makassar Strait. Specifically, the time interval from ca. 2000 to 800 yr ago was marked predominantly by higher densities at the northern end relative to the southern end of the strait, suggesting reduced heat flux from the Pacific to the Indian Ocean. This is consistent with previous work showing that this time interval was also marked by frequent El Niño conditions. Conversely, the period from ca. 800 to 300 yr ago, including the LIA, was marked by frequent periods when surface density was higher at the southern end of the strait, indicative of enhanced heat flux to the Indian Ocean. STUDY NOTES: Mg/Ca and stable oxygen isotope compositions of the planktonic foraminifer Globigerinoides ruber over the past 2000 years, sampled from two sediment cores collected at the northern and southern ends of the Makassar Strait, Indonesia. Sample preparation: Samples were freeze-dried, then soaked in a Calgon-water solution, before being washed through a 63um sieve. Samples were dried and the surface dwelling G. ruber were picked from the 250 to 350 um size fraction. Trace metal analysis: All samples used for trace metal analyses underwent the rigorous cleaning procedure of Boyle (1981) to eliminate clay and organic matter contamination, although the reductive cleaning step was not used. Calcium and magnesium were measured simultaneously using a Jobin Yvon Ultima Inductively Coupled Plasma Atomic Emission Spectrometer (ICP-AES). Based on repeated analysis of standards, the 1S analytical precision is better than 1.0%. Stable isotope analysis: All stable isotope measurements were made using a VG Optima stable isotope ratio mass spectrometer equipped with an automated carbonate system. All d18O values are reported in delta notation relative to the Vienna Pee Dee Belemnite (VPDB) standard. The long-term standard reproducibility for oxygen isotopes based on replicate analyses of a reference standard is ±0.07%. Age model: Radiocarbon analyses were performed at the Center for Atomic Mass Spectrometry at Lawrence Livermore National Laboratory on mixed samples of G. ruber and G. sacculifer from the >150 um size fraction. The calendar ages listed were calibrated using the Calib 5.0 program (Stuiver and Riemer, 2003), with an additional reservoir age correction of 75±80 years (Southon et al., 2002). Core MD98-2160: 05°12.07'S, 117°29.20'E, water depth 1185 m Core MD98-2177: 01°24.20'N, 119°04.68'E, water depth 968 m NCDC-Paleoclimatology https://www.ncdc.noaa.gov/data-access/paleoclimatology-data - Bauer Bruce Investigator : Newton, A. Investigator : Thunell, R.C. Investigator : Stott, L.D. 2012-04-26 ONLINE Files online, ASCII https://www.ncdc.noaa.gov/paleo/study/12906 https://www1.ncdc.noaa.gov/pub/data/paleo/contributions_by_author/newton2011/newton2011.txt https://www1.ncdc.noaa.gov/pub/data/paleo/contributions_by_author/newton2011/newton2011.xls https://www1.ncdc.noaa.gov/pub/data/paleo/contributions_by_author/newton2011/newton2011.txt https://www1.ncdc.noaa.gov/pub/data/paleo/contributions_by_author/newton2011/newton2011.xls English https://www.ncdc.noaa.gov/paleo/study/12906 https://www1.ncdc.noaa.gov/pub/data/paleo/contributions_by_author/newton2011/newton2011.txt https://www1.ncdc.noaa.gov/pub/data/paleo/contributions_by_author/newton2011/newton2011.xls Newton, A., R. Thunell, and L. Stott. 2011. Changes in the Indonesian Throughflow during the past 2000 yr. Geology, Vol. 39, January 2011, pp. 63-66, doi:10.1130/G31421.1 START YEAR: 2000 cal yr BP * END YEAR: 10 cal yr BP 117.48 -5.2 119.078 1.4033