The changing roles of iron and vertical mixing in regulating nitrogen and silicon cycling in the Southern Ocean over the last glacial cycle

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doi: 10.1002/2014PA002686
Author(s): Robinson, Rebecca S.; Brzezinski, Mark A.; Beucher, Charlotte P.; Horn, Matthew G. S.; Bedsole, Patrick
Author Affiliation(s): Primary:
University of Rhode Island, Graduate School of Oceanography, Narragansett, RI, United States
Other:
University of California at Santa Barbara, United States
Volume Title: Paleoceanography
Source: Paleoceanography, 29(12), p.1179-1195. Publisher: American Geophysical Union, Washington, DC, United States. ISSN: 0883-8305 CODEN: POCGEP
Note: In English. NSF Grant NSF OCE-00752191. 77 refs.; illus., incl. 1 table, sketch maps
Summary: The Southern Ocean plays a critical role in the air-sea CO2 balance through biological and physical mechanisms. Vertical supply of deep waters returns nutrients and CO2 to the surface and stimulates phytoplankton growth. Photosynthesis in the Southern Ocean is limited by iron and only a fraction of the carbon and nutrients that return to the surface are consumed for potential sequestration in the deep sea. Here we present the most spatially extensive data set of silicon and nitrogen isotope measurements from diatom frustules to date to examine the controls on nutrient drawdown during the last glacial period and across the glacial termination in both the Antarctic and Subantarctic zones. The new data confirm existing views that differing silicon and nitrate consumption patterns in the Antarctic zone are likely the result, at least in part, of iron addition during the last glacial maximum (LGM). However, earlier in the glacial, a more coordinated response in the two proxy records, with both reflecting enhanced consumption during episodes of increased iron accumulation and export production, implies a different system response than observed for the LGM. A collapse of the expected equatorward gradient in silicon isotope values and contraction of the nitrogen isotope gradient during the deglaciation suggests that nutrient supply increased not only in the Antarctic Zone, but also in the Subantarctic, perhaps due to enhanced deep mixing locally. Enhanced deep water ventilation across the Southern Ocean likely increased the nutrient content of mode waters during the deglaciation. Abstract Copyright (2014), . American Geophysical Union. All Rights Reserved.
Year of Publication: 2014
Research Program: ODP Ocean Drilling Program
Key Words: 02 Geochemistry; 24 Surficial Geology, Quaternary Geology; Atlantic Ocean; Cenozoic; Cores; Deglaciation; Geochemical cycle; Iron; Isotope ratios; Isotopes; Last glacial maximum; Leg 177; Marine environment; Marine sediments; Metals; N-15/N-14; Nitrogen; Nitrogen cycle; Nutrients; ODP Site 1094; Ocean Drilling Program; Paleo-oceanography; Paleoclimatology; Paleoecology; Paleoenvironment; Pleistocene; Quaternary; Sediments; Si-30/Si-28; Silicon; Silicon cycle; South Atlantic; Southern Ocean; Stable isotopes; Upper Pleistocene
Coordinates: S531049 S531049 E0050749 E0050749
S630600 S630600 W1350600 W1350600
S615400 S615400 W1695400 W1695400
S560600 S560600 W1150600 W1150600
Record ID: 2015016317
Copyright Information: GeoRef, Copyright 2017 American Geosciences Institute. Reference includes data from John Wiley & Sons, Chichester, United Kingdom