Deepwater expansion and enhanced remineralization in the eastern equatorial Pacific during the last glacial maximum
Umling, Natalie E.
Thunell, Robert C.
MetadataShow full item record
Published estimates of the radiocarbon content of middepth waters suggest a decrease in ventilation in multiple locations during the last glacial maximum (LGM; 24.0–18.1 ka). Reduced glacial ventilation would have allowed respired carbon to accumulate in those waters. A subsequent deglacial release of this respired carbon reservoir to the atmosphere could then account for the observed increases in atmospheric CO2 and decline in atmospheric radiocarbon content. However, age model error and a release of 14C‐depleted mantle carbon have also been cited as possible explanations for the observed middepth radiocarbon depletions, calling into question the deep ocean's role in storing respired carbon during the LGM. Joint measurements of benthic foraminiferal carbon isotope values (δ13C) and cadmium/calcium (Cd/Ca) ratios provide a method for isolating the air‐sea component of a water mass from changes in remineralization. Here we use benthic foraminiferal δ13C and Cd/Ca records from the eastern equatorial Pacific to constrain changes in remineralization and water‐mass mixing over the last glacial‐interglacial transition. These records are complemented with elemental measurements of the authigenic coatings of foraminifera to monitor postdepositional changes in bottom water properties. Our results suggest an increase of deep waters at midwater depths consistent with a shoaling of the boundary between the upper and lower branches of Southern Ocean overturning circulation. Additionally, our records demonstrate increased organic matter remineralization in middepth waters during the LGM, suggesting that respired carbon did accumulate in middepth waters under periods of reduced ventilation.
Author Posting. © American Geophysical Union, 2018. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Paleoceanography and Paleoclimatology 33 (2018): 563-578, doi:10.1029/2017PA003221.
Suggested CitationArticle: Umling, Natalie E., Thunell, Robert C., Bizimis, Michael, "Deepwater expansion and enhanced remineralization in the eastern equatorial Pacific during the last glacial maximum", Paleoceanography and Paleoclimatology 33 (2018): 563-578, DOI:10.1029/2017PA003221, https://hdl.handle.net/1912/10511
Showing items related by title, author, creator and subject.
Inferring ocean circulation during the Last Glacial Maximum and last deglaciation using data and models Amrhein, Daniel E. (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 2016-09)Since the Last Glacial Maximum (LGM, ~ 20,000 years ago) air temperatures warmed, sea level rose roughly 130 meters, and atmospheric concentrations of carbon dioxide increased. This thesis combines global models and ...
Jackson, Rebecca H.; Straneo, Fiamma (American Meteorological Society, 2016-09-01)In Greenland’s glacial fjords, heat and freshwater are exchanged between glaciers and the ocean. Submarine melting of glaciers has been implicated as a potential trigger for recent glacier acceleration, and observations ...
Kromer, Bernd; Friedrich, Michael; Hughen, Konrad A.; Kaiser, K. Felix; Remmele, Sabine; Schaub, Matthias; Talamo, Sahra (Dept. of Geosciences, University of Arizona, 2004)We built a floating, 1382-ring pine chronology covering the radiocarbon age interval of 12,000 to 10,650 BP. Based on the strong rise of Δ14C at the onset of the Younger Dryas (YD) and wiggle-matching of the decadal-scale ...