Ocean Oxygen and Nitrogen Cycle Model Simulations 
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               World Data Center for Paleoclimatology, Boulder
                                  and
                     NOAA Paleoclimatology Program
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NOTE: PLEASE CITE ORIGINAL REFERENCE WHEN USING THIS DATA!!!!!


NAME OF DATA SET: Ocean Oxygen and Nitrogen Cycle Model Simulations
LAST UPDATE: 8/2008 (Original receipt by WDC Paleo)
CONTRIBUTOR: Andreas Schmittner, Oregon State University 
IGBP PAGES/WDCA CONTRIBUTION SERIES NUMBER: 2008-075

WDC PALEO CONTRIBUTION SERIES CITATION: 
Schmittner, A., et al. 2008.
Ocean Oxygen and Nitrogen Cycle Model Simulations.
IGBP PAGES/World Data Center for Paleoclimatology 
Data Contribution Series # 2008-075. 
NOAA/NCDC Paleoclimatology Program, Boulder CO, USA.


ORIGINAL REFERENCE:  Schmittner, A., E.D. Galbraith, S.W. Hostetler, 
T.F. Pederson, and R. Zhang. 2007. 
Large fluctuations of dissolved oxygen in the Indian and Pacific 
oceans during Dansgaard-Oeschger oscillations caused by variations 
of North Atlantic Deep Water subduction. 
Paleoceanography, 22, PA3207, doi:10.1029/2006PA001384.
  
ABSTRACT:
Paleoclimate records from glacial Indian and Pacific oceans sediments 
document millennial-scale fluctuations of subsurface dissolved oxygen 
levels and denitrification coherent with North Atlantic temperature
oscillations. Yet the mechanism of this teleconnection between the 
remote ocean basins remains elusive. Here we present model simulations 
of the oxygen and nitrogen cycles that explain how changes in deepwater
subduction in the North Atlantic can cause large and synchronous 
variations of oxygen minimum zones throughout the Northern Hemisphere 
of the Indian and Pacific oceans, consistent with the paleoclimate records.  
Cold periods in the North Atlantic are associated with reduced nutrient 
delivery to the upper Indo-Pacific oceans, thereby decreasing productivity. 
Reduced export production diminishes subsurface respiration of organic 
matter leading to higher oxygen concentrations and less denitrification. 
This effect of reduced oxygen consumption dominates at low latitudes. 
At high latitudes in the Southern Ocean and North Pacific, increased 
mixed layer depths and steepening of isopycnals improve ocean ventilation 
and oxygen supply to the subsurface. Atmospheric teleconnections through 
changes in wind-driven ocean circulation modify this basin-scale pattern 
regionally. These results suggest that changes in the Atlantic Ocean 
circulation, similar to those projected by climate models to possibly 
occur in the centuries to come because of anthropogenic climate warming, 
can have large effects on marine ecosystems and biogeochemical cycles 
even in remote areas.


ADDITIONAL REFERENCE:
Weaver, A. J., et al. 2001.  
The UVic Earth System Climate Model: Model description, 
climatology and applications to past, present and future climates. 
Atmos. Ocean, 39, 361– 428.


GEOGRAPHIC REGION: Global
PERIOD OF RECORD:  N/A

FUNDING SOURCES: 
A.S. and S.H. were supported by the paleoclimate program of the 
US National Science Foundation as part of the PALEOVAR project (ATM-0602395).



DESCRIPTION:   
Detailed, three-dimensional ocean simulations of oxygen and nitrogen 
cycling during idealized Dansgaard-Oeschger oscillations using the 
University of Victoria Earth System Climate Model [Weaver et al., 2001], 
Version 2.7.  The model includes an improved version of a simple ocean 
ecosystem model with two phytoplankton classes (nitrogen fixers and 
other phytoplankton), two nutrients (NO3 and PO4) as well as explicit 
representations of denitrification in the water column and nitrogen fixation. 

Simulations of Dansgaard-Oeschger Events Changes in deepwater formation 
are triggered by applying a perturbation to the surface freshwater 
balance in the North Atlantic for 500 years.  Deepwater formation in the 
North Atlantic ceases for ~1000 years as a response to this freshwater 
forcing and subsequently returns to its initial state.  The simulated 
response of the climate system, characterized by strong cooling and 
increased sea ice cover in the North Atlantic (particularly in winter) 
and warming of thermocline waters in the Southern Hemisphere, is 
consistent with paleoclimate proxy records of stadial conditions.
Reduced supply of deep nutrient-rich waters to the Indian and Pacific 
euphotic zones leads to a decline of export production by about 30% 
in the stadial simulation.



DATA:
Complete model output in netCDF format are contained in the file:
ftp://ftp.ncdc.noaa.gov/pub/data/paleo/gcmoutput/uvic/schmittner2007/model_output.nc   (125MB file size)

Individual ASCII text files for select parameters, depths, and times are located at:
ftp://ftp.ncdc.noaa.gov/pub/data/paleo/gcmoutput/uvic/schmittner2007/asciifiles/

ASCII file names consist of codes for the output variable name, ZT (depth, m) and year, 
as follows:

NUTR: nutrients
O2: oxygen
SALINITY: ocean salinity
TEMP: ocean potential temperature (°K)
U: eastward ocean velocity (m/s) 
V: northward ocean velocity (m/s)