DOI: 10.25921/613t-gr84
title: NOAA/WDS Paleoclimatology - North Atlantic Freshwater Forcing Model Data at 8.2ka

description: We compared four simulations of the 8.2 ka event to assess climate model sensitivity and skill in responding to North Atlantic freshwater perturbations. All of the simulations used the same freshwater forcing, 2.5 Sv for one year, applied to either the Hudson Bay (northeastern Canada) or Labrador Sea (between Canada's Labrador coast and Greenland). This freshwater pulse induced a decadal-mean slowdown of 10–25% in the Atlantic Meridional Overturning Circulation (AMOC) of the models and caused a large-scale pattern of climate anomalies that matched proxy evidence for cooling in the Northern Hemisphere and a southward shift of the Intertropical Convergence Zone. The multi-model ensemble generated temperature anomalies that were just half as large as those from quantitative proxy reconstructions, however. Also, the duration of AMOC and climate anomalies in three of the simulations was only several decades, significantly shorter than the duration of ~150 yr in the paleoclimate record. Possible reasons for these discrepancies include incorrect representation of the early Holocene climate and ocean state in the North Atlantic and uncertainties in the freshwater forcing estimates.
description: File names generally follow CMIP5/PMIP3 conventions, using the following abbreviations:
 
 Omon = ocean variables at monthly resolution (sea surface temperature, sea surface salinity, sea ice area percent)
 Oyr = ocean variables at annual resolution (meridional overturning streamfunction)
 Amon = atmosphere variables at monthly resolution (near surface air temperature, precipitation)
 Ayr = atmosphere variables at annual resolution (near surface air temperature, precipitation)

 ehControl = Early Holocene (8.5 ka) control simulation
 ehMWP = Early Holocene meltwater pulse experiment
 piControl = PreIndustrial control simulation
 piMWP = PreIndustrial meltwater pulse experiment
 
 r<N>i<M>p<L> = Ensemble member designation, with N representing realization number, M representing initial condition method, and L representing "perturbed physics" number
 
 Note that GISS Model-E-R output are provided as multi-decadal or decadal averages of either monthly (Omon, Amon) or annual (Oyr) means. 
 Multi-decadal (30-year) averages are provided for the control simulation and decadal (10-year) averages for the meltwater pulse experiment. 
 Also, please note that anomalies for the GISS Model-E-R must be calculated as the 10-yr mean of the MWP experiment less the 30-yr mean of the closest control years. 
 See provided ncl scripts (fig1_Morrill_etal_2013.ncl, etc) for more details on how to calculate GISS Model-E-R anomalies.

  DATA FILE LIST (sizes in MB and names)
 
 0.1	8ka-precip-ensemble.nc
 0.1	8ka-temp-ensemble.nc
 68.9 	CCSM_Amon_ehControl_r1i1p1.nc
 69.0	CCSM_Amon_ehControl_r1i2p1.nc
 34.5	CCSM_Amon_ehMWP_r1i1p1.nc
 69.0	CCSM_Amon_ehMWP_r1i2p1.nc
 851.5 	CCSM_Omon_ehControl_r1i1p1.nc
 853.7	CCSM_Omon_ehControl_r1i2p1.nc
 426.7 	CCSM_Omon_ehMWP_r1i1p1.nc
 427.4   CCSM_Omon_ehMWP_r1i2p1.nc
 15.0	CCSM_Oyr_ehControl_r1i1p1.nc
 20.0	CCSM_Oyr_ehControl_r1i2p1.nc
 5.0 	CCSM_Oyr_ehMWP_r1i1p1.nc
 10.0	CCSM_Oyr_ehMWP_r1i2p1.nc
 6.1	GISS-E-R_Amon_piControl_r1i1p1.nc
 5.5	GISS-E-R_Amon_piMWP_r1i1p1.nc
 4.4	GISS-E-R_Omon_piControl_r1i1p1.nc
 4.0	GISS-E-R_Omon_piMWP_r1i1p1.nc
 0.3	GISS-E-R_Oyr_piControl_r1i1p1.nc
 0.3	GISS-E-R_Oyr_piMWP_r1i1p1.nc
 8.3	LOVECLIM_Ayr_ehControl_r1i1p1.nc
 8.3	LOVECLIM_Ayr_ehMWP_r1i1p1.nc
 350.5	LOVECLIM_Omon_ehControl_r1i1p1.nc
 350.9	LOVECLIM_Omon_ehMWP_r1i1p1.nc
 1.4	LOVECLIM_Oyr_ehControl_r1i1p1.nc
 1.4	LOVECLIM_Oyr_ehMWP_r1i1p1.nc