Southern Ocean Carbon and Nitrogen Isotopic Ratios: Readme file
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               World Data Center for Paleoclimatology, Boulder
                                  and
                     NOAA Paleoclimatology Program
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NOTE: PLEASE CITE CONTRIBUTORS WHEN USING THIS DATA!!!!!

NAME OF DATA SET: Southern Ocean Carbon and Nitrogen Isotopic Ratios
LAST UPDATE: 3/2002 (Original Receipt by WDC Paleo)

CONTRIBUTOR: X. Crosta

IGBP PAGES/WDCA CONTRIBUTION SERIES NUMBER: 2002-014

SUGGESTED DATA CITATION: Crosta, X. and A. Shemesh, 2002,
Southern Ocean Carbon and Nitrogen Isotopic Ratios, 
IGBP PAGES/World Data Center for Paleoclimatology 
Data Contribution Series # 2002-014.
NOAA/NGDC Paleoclimatology Program, Boulder CO, USA.

ORIGINAL REFERENCE: 
Crosta, X. and Shemesh A., Reconciling down-core anti-correlation 
of diatom carbon and nitrogen isotopic ratios from the Southern Ocean. 
Paleoceanography, v.17, No.1, Feb. 2002.

GEOGRAPHIC REGION: Southern Ocean

PERIOD OF RECORD: Pleistocene

LIST OF FILES: Readme_crosta2002.txt (this file),
IO127710-PA565.txt, SO136111-PA565.txt (tab-delimited text files)
d15N and d13C data vs depth in cm.

DESCRIPTION:
Crosta and Shemesh Southern Ocean Carbon and Nitrogen Isotopic Ratios.

Core SO136-111
56 40' S, 160 14' E, 3912m. Water Depth

Core IO1270-10
52 20'S, 20 47'E, 2740m water depth

Abstract:
Oceanic nutrient cycling in the Southern Ocean is supposed to have an 
important impact on glacial-interglacial atmospheric CO2 changes and 
global climate. In order to characterize such nutrient cycling over the 
last two climatic cycles, we investigated carbon and nitrogen isotopic 
ratios of diatom-bound organic matter (d13Cdiat and d15Ndiat respectively) 
in two cores retrieved form the Atlantic and Indian sectors of the 
Antarctic Ocean.  The two cores show the same isotopic patterns. d13Cdiat 
values are depleted during glacial periods and enriched during 
interglacial periods indicating lower productivity during cold times. 
d15Ndiat values are enriched during glacial periods and depleted during 
interglacial periods arguing for greater nitrate utilization during cold 
times. Taken at face value, this apparent contradiction leads to opposite 
conclusions on the role of the Southern Ocean biological pump on the 
atmospheric CO2 changes. But, the two sets of data can be reconciled by a 
"sea ice   mixing rate scenario" that calls upon a balance between the 
effect of cutting off gas transfer at the ocean-atmosphere boundary and 
the effect of reducing vertical transport of nutrients through the 
pycnocline.