Southern Ocean Deep-Dea Coral Radiocarbon and U/Th Age Data over the Last 30,000 Years Hines, S.K.V.; Southon, J.R.; Adkins, J.F. Hines, S.K.V. Southon, J.R. Adkins, J.F. earth science/paleoclimate/paleoceanography (depth,null,null,meter,null,paleoceanography,null,null,N,coral collection depth) earth science/paleoclimate/paleoceanography (uranium/thorium,sediment,one standard deviation,calendar year before present,null,paleoceanography,corrected,inductively-coupled plasma mass spectrometry,N,U/Th age with initial 230Th correction) earth science/paleoclimate/paleoceanography (sample identification,null,null,null,null,paleoceanography,null,null,C,null) earth science/paleoclimate/paleoceanography (age,sediment,one standard deviation,radiocarbon year before present,null,paleoceanography,null,accelerator mass spectrometry,N,null) earth science/paleoclimate/paleoceanography (notes,null,null,null,null,paleoceanography,null,null,C,Lab code used for cutting and cleaning sample) earth science/paleoclimate/paleoceanography (age,sediment,null,radiocarbon year before present,null,paleoceanography,null,accelerator mass spectrometry,N,null) earth science/paleoclimate/paleoceanography (uranium/thorium,sediment,null,calendar year before present,null,paleoceanography,corrected,inductively-coupled plasma mass spectrometry,N,U/Th age with initial 230Th correction) earth science/paleoclimate/paleocean earth science/paleoclimate/paleocean earth science/paleoclimate/paleocean (Southern Ocean south of Tasmania>LATITUDE -45>LONGITUDE 148) The circulation of intermediate waters plays an important role in global heat and carbon transport in the ocean and changes in their distribution are closely tied to glacial-interglacial climate change. Coupled radiocarbon and U/Th measurements on deep-sea Desmophyllum dianthus corals allow for the reconstruction of past intermediate water ventilation. We present a high-resolution time series of Antarctic Intermediate Water radiocarbon from 44 corals spanning 30 ka through the start of the Holocene, encompassing the transition into the Last Glacial Maximum (LGM) and the last deglaciation. Corals were collected south of Tasmania from water depths between 1430 and 1950 m with 80% of them between 1500 and 1700 m, giving us a continuous record from a narrow depth range. The record shows three distinct periods of circulation: the MIS 3-2 transition, the LGM/Heinrich Stadial 1 (extending from ~22 to 16 kyr BP), and the Antarctic Cold Reversal (ACR). The MIS 3-2 transition and the ACR are characterized by abrupt changes in intermediate water radiocarbon while the LGM time period generally follows the atmosphere at a constant offset, in support of the idea that the LGM ocean was at steady state for its 14C distribution. Closer inspection of the LGM time period reveals a 40 permil jump at ~19 ka from an atmospheric offset of roughly 230 permil to 190 permil, coincident with an observed 10-15 m rise in sea level and a southward shift of the Subantarctic and Polar Fronts, an abrupt change not seen in deeper records. During the ACR time period intermediate water radiocarbon is on average less offset from the atmosphere (~110 permil) and much more variable. This variability has been captured within the lifetimes of three individual corals with changes of up to 35 permil over ~40 yr, likely caused by the movement of Southern Ocean fronts. This surprising result of relatively young and variable intermediate water radiocarbon during the ACR seems to go against the canonical idea of reduced circulation and ventilation in the south during this time period. However comparisons with other records from the Southern Ocean highlight zonal asymmetries, which can explain the deviation of our Tasmanian record from those in Drake Passage and the eastern Pacific. These signals seen in Tasmanian intermediate water 14C can also be found in Greenland ice core d18O and East Asian monsoon strength. Throughout the LGM and the deglaciation, our Tasmanian intermediate water record is sensitive to times when the upper and lower cells of the meridional overturning circulation are more or less interconnected, which has important implications for the global climate system on glacial-interglacial time scales. STUDY NOTES: Seamounts range in depth from 1000 to 1947 meters. NCDC-Paleoclimatology https://www.ncdc.noaa.gov/data-access/paleoclimatology-data - Bauer Bruce Investigator : Hines, S.K.V. Investigator : Southon, J.R. Investigator : Adkins, J.F. 2015-12-23 ONLINE Files online, ASCII https://www.ncdc.noaa.gov/paleo/study/19580 https://www1.ncdc.noaa.gov/pub/data/paleo/contributions_by_author/hines2015/hines2015.txt https://www1.ncdc.noaa.gov/pub/data/paleo/contributions_by_author/hines2015/hines2015.txt English https://www.ncdc.noaa.gov/paleo/study/19580 https://www1.ncdc.noaa.gov/pub/data/paleo/contributions_by_author/hines2015/hines2015.txt Hines, S.K.V, J.R. Southon, and J.F. Adkins2015A high-resolution record of Southern Ocean intermediate water radiocarbon over the past 30,000 yearsEarth and Planetary Science Letters43246-5810.1016/j.epsl.2015.09.038 START YEAR: 67500 cal yr BP * END YEAR: 8500 cal yr BP 144 -47 152 -43