South Atlantic TN057-13PC 30 KYr Nitrogen Data Horn, M.G.S.; Beucher, C.P.; Robinson, R.S.; Brzezinski, M.A. Horn, M.G.S. Beucher, C.P. Robinson, R.S. Brzezinski, M.A. biogeochemical cycles earth science/paleoclimate/paleoceanography (age,null,null,calendar kiloyear before present,null,paleoceanography,null,null,N,null) earth science/paleoclimate/paleoceanography (delta 15N,sediment,null,per mil,null,paleoceanography,null,null,N,null) earth science/paleoclimate/paleoceanography (nitrogen,sediment,null,micromole per gram,null,paleoceanography,null,null,N,null) earth science/paleoclimate/paleoceanography (nitrogen,diatom,null,micromole per gram,null,paleoceanography,null,null,N,diatom-bound nitrogen) earth science/paleoclimate/paleoceanography (depth,null,null,centimeter,null,paleoceanography,null,null,N,null) earth science/paleoclimate/paleoceanography (delta 15N,diatom,null,per mil,null,paleoceanography,null,null,N,diatom-bound organic matter) earth science/paleoclimate/paleocean earth science/paleoclimate/paleocean (TN057-13PC4>LATITUDE -53.1728>LONGITUDE 5.1275) The reinvigoration of overturning in the Southern Ocean is hypothesized to have returned CO2 from the deep ocean to the atmosphere at the end of the last ice age. Large peaks in opal accumulation have been put forward as evidence for an increase in wind driven upwelling between 10 and 15 ka. Here, we use coupled nitrogen and silicon isotope records alongside opal accumulation rates to provide quasi-quantitative estimates of Southern Ocean nutrient supply, by upwelling, and nutrient utilization across this interval. Significant changes in the consumption of N and Si across the two opal accumulation peaks indicate major changes in both upwelling and nutrient demand. We find N and Si consumption to be relatively incomplete during peak opal accumulation at the onset of the deglaciation. This indicates that nutrient supply was significantly enhanced. The second deglacial peak in opal accumulation is associated with more complete Si consumption and variable N consumption. We suggest that this peak represents strong upwelling and more complete utilization of the available silicic acid pool. Differences between the Si and N responses during opal peaks may stem from decreasing iron availability across the glacial termination. The nutrient isotope evidence for excess nutrients during the deglaciation indicates that the high export productivity was insufficient to overcome the evasion of CO2 to the atmosphere as a result of physical circulation changes. Previous work has demonstrated that the reinvigoration of overturning circulation during the deglaciation causes a transient peak in nutrient supply to the low latitudes. This is supported by our data, which indicate that relatively high macronutrient concentrations were maintained in the Southern Ocean surface waters that are incorporated into mode waters despite high demand. STUDY NOTES: Bulk sedimentary and diatom-bound N isotope values for South Atlantic core TN057-13PC spanning the last 30 ky, based on previously published ages. Bulk d15N was measured by EA-IRMS. Diatom-bound d15N was measured after physical and chemical cleaning of the diatom-opal by the persulfate-denitrifier method. NCDC-Paleoclimatology https://www.ncdc.noaa.gov/data-access/paleoclimatology-data - Bauer Bruce Investigator : Horn, M.G.S. Investigator : Beucher, C.P. Investigator : Robinson, R.S. Investigator : Brzezinski, M.A. 2012-12-03 ONLINE Files online, ASCII https://www.ncdc.noaa.gov/paleo/study/13545 https://www1.ncdc.noaa.gov/pub/data/paleo/contributions_by_author/horn2011/horn2011.txt https://www1.ncdc.noaa.gov/pub/data/paleo/contributions_by_author/horn2011/horn2011.txt English https://www.ncdc.noaa.gov/paleo/study/13545 https://www1.ncdc.noaa.gov/pub/data/paleo/contributions_by_author/horn2011/horn2011.txt Matthew G. Horn, Charlotte P. Beucher, Rebecca S. Robinson, Mark A. Brzezinski. 2011. Southern ocean nitrogen and silicon dynamics during the last deglaciation. Earth and Planetary Science Letters, Vol. 310, Issues 3-4, pp. 334-339. DOI: 10.1016/j.epsl.2011.08.016 START YEAR: 29320 cal yr BP * END YEAR: 0 cal yr BP 5.1275 -53.1728 5.1275 -53.1728