Atlantic Ocean Abyssal Circulation Model Code ----------------------------------------------------------------------- World Data Center for Paleoclimatology, Boulder and NOAA Paleoclimatology Program ----------------------------------------------------------------------- NOTE: PLEASE CITE ORIGINAL REFERENCE WHEN USING THIS DATA!!!!! NAME OF DATA SET: Atlantic Ocean Abyssal Circulation Model Code LAST UPDATE: 10/2008 (Original receipt by WDC Paleo) CONTRIBUTOR: Olivier Marchal, Woods Hole Oceanographic Institution IGBP PAGES/WDCA CONTRIBUTION SERIES NUMBER: 2008-099 WDC PALEO CONTRIBUTION SERIES CITATION: Marchal, O. and W.B. Curry. 2008. Atlantic Ocean Abyssal Circulation Model Code. IGBP PAGES/World Data Center for Paleoclimatology Data Contribution Series # 2008-099. NOAA/NCDC Paleoclimatology Program, Boulder CO, USA. ORIGINAL REFERENCE: Marchal, O. and W.B. Curry. 2008. On the abyssal circulation in the glacial Atlantic. Journal of Physical Oceanography, 38, 2014-2037. doi:10.1175/2008JPO3895.1. ABSTRACT: An inverse method is used in order to evaluate the information contained in sediment data for the Atlantic basin during the Last Glacial Maximum (defined here as the time interval 18–21 kyr before present). The data being considered are an updated compilation of the isotopic ratios 18O/16O (d18O) and 13C/12C (d13C) of fossil shells of benthic foraminifera (bottom-dwelling organisms). First, an estimate of the abyssal circulation in the modern Atlantic is obtained, which is consistent with (i) climatologies of temperature and salinity of the World Ocean Circulation Experiment, (ii) observational estimates of volume transport at specific locations, and (iii) the statements of a finite-difference geostrophic model. Second, estimates of water properties (d18O of equilibrium calcite or d18Oc and d13C of dissolved inorganic carbon or d13CDIC) derived from sediment data are combined with this circulation estimate in order to test their consistency with the modern flow. We find that more than ca. 80% of water property estimates (d18Oc or d13CDIC) appear compatible with the modern flow given their uncertainties. The null hypothesis of a consistency of glacial d13CDIC estimates with the modern flow can be rejected at the 5% significance level after two assumptions are made (besides normality): (i) the uncertainty in these estimates is ±0.1 per mil (this uncertainty includes errors in sediment core chronology and oceanic representativity of benthic d13C which alone appears better than this value on average); and (ii) d13CDIC in the glacial deep Atlantic was dominated by a balance between water advection and organic C remineralization. Measurements of d13C on benthic foraminifera are clearly useful, but the current uncertainties in the distribution and budget of d13CDIC in the glacial Atlantic must be reduced in order to increase the power of the test. GEOGRAPHIC REGION: Atlantic Ocean PERIOD OF RECORD: N/A FUNDING SOURCE: US National Science Foundation DESCRIPTION: Computer code which has been developed to produce results described in Marchal and Curry (2008). The code is written in Fortran and has been run using F90. The code allows one to conduct at least two tasks: -to produce an estimate of the abyssal circulation in the Atlantic Ocean by combining hydrographic observations and a finite difference circulation model. - to combine this circulation estimate with paleoceanographic observations from the sediment (equilibrium calcite d18O or d18O_c and d13C of dissolved inorganic carbon or d13C_dic) for testing the consistency of these observations with the modern circulation. The code could easily be modified to conduct a similar test for other paleoceanographic tracers. The code includes a total of 63 files: *.f : 35 source files makefile: 1 file to link all source files start.* : 2 examples of file to run the code *.d : 8 data files produced from WOCE climatology and ETOPO5 bathymetry *.hol : 8 data files including objectively mapped d18O_c or d13C_dic for Holocene (derived from sediment data) *.gla : 8 data files including objectively mapped d18O_c or d13C_dic for LGM (derived from sediment data) main.j : 1 file to compile and execute start.ref: Used to produce an estimate of abyssal circulation in modern Atlantic start.c13_0p1_gla: Used to combine objectively mapped d18O_c or d13C_dic for Holocene or LGM with the modern circulation Running the code requires sufficient storage capability. This is largely dictated by the grid resolution set in commonvar.f (itot,jtot,ktot) Running the code requires access to IBM Mathematical Library ESSL. More specifically the code includes calls to the following routines: - dpotrs - dpotrf - dtrtri - dges - dgef The code could easily be modified to include calls to routines from other libraries. DATA: The 63 code files described above can be downloaded from the NOAA/WDC Paleoclimatology archive in the directory: ftp://ftp.ncdc.noaa.gov/pub/data/paleo/softlib/abyssal-circ/code-files/ They are also contained in a single tar file: ftp://ftp.ncdc.noaa.gov/pub/data/paleo/softlib/abyssal-circ/abyssal-circ.tar