Eastern Equatorial Pacific 40KYr Nitrogen Isotope Data Robinson, R.S.; Martinez, P.; Pena, L.D.; Cacho, I. Robinson, R.S. Martinez, P. Pena, L.D. Cacho, I. biogeochemical cycles earth science/paleoclimate/paleoceanography (depth,null,null,meter,null,paleoceanography,composited,null,N,null) 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 AIR,null,paleoceanography,null,isotope ratio mass spectrometry,N,null) earth science/paleoclimate/paleoceanography (nitrogen,sediment,null,percent,null,paleoceanography,null,isotope ratio mass spectrometry,N,null) earth science/paleoclimate/paleocean (TR163-22>LATITUDE .52>LONGITUDE -92.4) (ODP1240>LATITUDE .167>LONGITUDE -86.4667) The Eastern Equatorial Pacific (EEP) is a high nutrient-low chlorophyll region of the ocean. Downcore nitrogen isotope records from the EEP have been previously interpreted as a direct reflection of changes in nutrient consumption. However, the observed changes in sedimentary d15N since the last glacial maximum have no coherent relationship with export productivity or an inferred variation in the iron-to-nitrate ratio of the surface waters. Rather, downcore N isotope records in the EEP strongly resemble changes in the extent of water column denitrification as recorded in nearby sedimentary d15N records along the western margin of the Americas. This similarity is attributed to the overprinting of the N isotopic composition of nitrate in the EEP through the advection of nitrate westward from the margins in the subsurface. A local nitrogen isotope record of changes in the degree of nutrient consumption is extracted from the bulk sedimentary record by subtracting two different sedimentary d15N records of denitrification changes from two new EEP d15N records (TR163-22 and ODP Site 1240). The denitrification records used are from 1) the Central American margin (ODP Site 1242) and 2) the South American margin (GeoB7139-2). The degree of consumption in the surface waters declines rapidly from elevated values during the last glacial maximum to a pair of minima around 15 and 11–13 ka, and finally it increases into the Holocene. The derived EEP nitrogen isotope record indicates that the regional peak in export productivity occurred when the supply of nutrients exceeded the apparently high demand. The influx of nutrients during the deglaciation is attributed to the resumption of intense overturning in the Southern Ocean and the release of sequestered CO2 and nutrient- rich, O2 poor waters from the deep ocean. This has important implications for understanding the glacial-interglacial scale variation in intermediate water suboxia and water column denitrification. STUDY NOTES: Bulk sedimentary nitrogen isotope and nitrogen content data from piston core TR163-22 and ODP Site 1240 in the eastern equatorial Pacific Ocean. All nitrogen content and isotope data were measured by EA-IRMS on bulk sediment. NCDC-Paleoclimatology https://www.ncdc.noaa.gov/data-access/paleoclimatology-data - Bauer Bruce Investigator : Robinson, R.S. Investigator : Martinez, P. Investigator : Pena, L.D. Investigator : Cacho, I. 2010-05-20 ONLINE Files online, ASCII https://www.ncdc.noaa.gov/paleo/study/10491 https://www1.ncdc.noaa.gov/pub/data/paleo/contributions_by_author/robinson2009/robinson2009.xls https://www1.ncdc.noaa.gov/pub/data/paleo/contributions_by_author/robinson2009/robinson2009.txt https://www1.ncdc.noaa.gov/pub/data/paleo/contributions_by_author/robinson2009/robinson2009.xls https://www1.ncdc.noaa.gov/pub/data/paleo/contributions_by_author/robinson2009/robinson2009.txt English https://www.ncdc.noaa.gov/paleo/study/10491 https://www1.ncdc.noaa.gov/pub/data/paleo/contributions_by_author/robinson2009/robinson2009.xls https://www1.ncdc.noaa.gov/pub/data/paleo/contributions_by_author/robinson2009/robinson2009.txt Robinson, R.S., P. Martinez, L.D. Pena, and I. Cacho. 2009. Nitrogen isotopic evidence for deglacial changes in nutrient supply in the eastern equatorial Pacific. Paleoceanography, 24, PA4213, doi:10.1029/2008PA001702. START YEAR: 41430 cal yr BP * END YEAR: 2190 cal yr BP -92.4 .167 -86.4667 .52