Low Indian native Pichevin

Core/Site name:

MD-04 2876 Pakistan Margin

Country/Region:

Arabian Sea

Elevation:

-828

Archive:

marine sediments (downcore)

Proxy measurement:

weight % nitrogen, nitrogen isotope, weight % organic carbon

Sampling resolution:

centennial

Climate sensitivity:

productivity, mixing

Dating resolution:

15 dates/50,000 years

Dating information:

radiometric

Startyear:

178 BP

Endyear:

46274 BP

Description:

DESCRIPTION: Nitrogen content and isotopic composition plus organic carbon content in sediments from core MD-04 2876 on the Pakistan Margin of the Arabian Sea, within the present day Oxygen Minimum Zone (OMZ). Comparison of these records with previously published d15N data from the Arabian Sea demonstrate regional spatial and temporal variability in Arabian Sea denitrification. ABSTRACT: Modern seawater profiles of oxygen, nitrate deficit, and nitrogen isotopes reveal the spatial decoupling of summer monsoon-related productivity and denitrification maxima in the Arabian Sea (AS) and raise the possibility that winter monsoon and/or ventilation play a crucial role in modulating denitrification in the northeastern AS, both today and through the past. A new high-resolution 50-ka record of d15N from the Pakistan margin is compared to five other denitrification records distributed across the AS. This regional comparison unveils the persistence of east-west heterogeneities in denitrification intensity across millennial-scale climate shifts and throughout the Holocene. The oxygen minimum zone (OMZ) experienced east-west swings across Termination I and throughout the Holocene. Probable causes are (1) changes in ventilation due to millennial-scale variations in Antarctic Intermediate Water formation and (2) postglacial reorganization of intermediate circulation in the northeastern AS following sea level rise. Whereas denitrification in the world's OMZs, including the western AS, gradually declined following the deglacial maximum (10-9 ka BP), the northeastern AS record clearly witnesses increasing denitrification from about 8 ka BP. This would have impacted the global Holocene climate through sustained N2O production and marine nitrogen loss.

Data entered by name:

Saenger, Casey

Data entered by email:

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Main reference(s):

Pichevin, L., E. Bard, P. Martinez, and I. Billy. 2007. Evidence of ventilation changes in the Arabian Sea during the late Quaternary: Implication for denitrification and nitrous oxide emission. Global Biogeochem. Cycles, 21, GB4008, doi:10.1029/2006GB002852.

Link to reference 1:

http://www.agu.org/pubs/crossref/2007/2006GB002852.shtml

Data storage link 1:

ftp://ftp.ncdc.noaa.gov/pub/data/paleo/contributions_by_author/pichevin2007/pichevin2007.txt

Current dating method:

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Annual snow acc rate:

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Category: Ocean2k