LOVECLIM Earth System Model Last Glacial Maximum oceanic d13C and D14C data Menviel, L. Menviel, L. earth science/paleoclimate/paleoclimatic modeling (latitude,null,null,degree north,null,paleoclimatic modeling,null,null,N,null) earth science/paleoclimate/paleoclimatic modeling (Delta 14C,sea water,null,dimensionless,null,paleoclimatic modeling,null,null,N,null) earth science/paleoclimate/paleoclimatic modeling (longitude,null,null,degree east,null,paleoclimatic modeling,null,null,N,null) earth science/paleoclimate/paleoclimatic modeling (delta 13C,sea water,null,per mil,null,paleoclimatic modeling,null,null,N,null) earth science/paleoclimate/model (Global>LATITUDE >LONGITUDE ) Atmospheric CO2 was ∼90 ppmv lower at the Last Glacial Maximum (LGM) compared to the late Holocene, but the mechanisms responsible for this change remain elusive. Here we employ a carbon isotope-enabled Earth System Model to investigate the role of ocean circulation in setting the LGM oceanic δ13C distribution, thereby improving our understanding of glacial/interglacial atmospheric CO2 variations. We find that the mean ocean δ13C change can be explained by a 378 ± 88 Gt C(2σ) smaller LGM terrestrial carbon reservoir compared to the Holocene. Critically, in this model, differences in the oceanic δ13C spatial pattern can only be reconciled with a LGM ocean circulation state characterized by a weak (10–15 Sv) and relatively shallow (2000–2500 m) North Atlantic Deep Water cell, reduced Antarctic Bottom Water transport (≤10 Sv globally integrated), and relatively weak (6–8 Sv) and shallow (1000–1500 m) North Pacific Intermediate Water formation. This oceanic circulation state is corroborated by results from the isotope-enabled Bern3D ocean model and further confirmed by high LGM ventilation ages in the deep ocean, particularly in the deep South Atlantic and South Pacific. This suggests a poorly ventilated glacial deep ocean which would have facilitated the sequestration of carbon lost from the terrestrial biosphere and atmosphere. STUDY NOTES: This dataset is a collection of outputs of numerical simulations performed with LOVECLIM, an Earth System Model. The model was forced with Last Glacial Maximum (~20 ka B.P.) boundary conditions (orbital parameters, ice-sheet topogra phy and albedo, CO2, d13CO2 and D14CO2). The dataset are oceanic d13C values for 28 Last Glacial Maximum (LGM) experiments, as well as oceanic D14C values fo r a subset of the LGM experiments. d13C and D14C values are the isotopic signatures of oceanic DIC and respectively represent a measure of the ratio of stable isotopes 13C and radioactive isotope 14C with respect to the standard . Both are reported in parts per thousand. LOVECLIM is an acronym made from the names of the five different models that have been coupled to built the Earth sy stem model: LOch-Vecode-Ecbilt-CLio-agIsm Model (LOVECLIM). LOVECLIM 1.2 includes representations of the atmosphere, the ocean and sea ice, the land surface (including vegetation), the ice sheets, the icebergs and the carbon cycle. The atmospheric component is ECBilt2, a T21, 3-level quasi-geostrophic model. The oceanic component is CLIO3, which is made up of an ocean general circulation model coupled to a comprehensive thermodynamic-dynamic sea-ice model. Its horizontal resolution is 3° y 3°, and there are 20 levels in the ocean. ECBilt-CLIO is coupled to VECODE, a vegetat ionmodel that simulates the dynamics of two main terrestrial plant functional types, trees and grasses, as well as d esert. VECODE also simulates the evolution of the carbon cycle over land while the oceanic carbon cycle is represent ed in LOCH, a comprehensive model that takes into account both the solubility and biological pumps. LOVECLIM description is an extract from http://www.academia.edu/12279222/Description_of_the_Earth_system_model_of_in termediate_complexity_LOVECLIM_version_1.2 Reference: Menviel, L., J. Yu, F. Joos, A. Mouchet, K. Meissner, M. England, "Poorly ventilated deep ocean at the La st Glacial Maximum inferred from carbon isotopes: a data-model comparison study", 2016, Paleoceanography,2016PA00302 4, under Review. 3 dimensional netcdf data of dc13 (permil, c13_X.nc) and DC14 (permil, c14_X.nc), where X denotes the name of the ex periments described in Tables 1 and S1. PI denotes the pre-industrial control run. Experiments list from reference paper V1 52 ± 53GtC NADW, AABW, SO XP, CT V1L S S - -142 V1LNAoff Off I - -19 V1LNAw W I - -22 V1LNAwSOw I I - -6 V1LNAwSOs I S - -75 V1LNAwGR I I +9% -17 V2 205 ± 47GtC NADW, AABW, SO XP, CT V2L S I - 171 V2LNAoff Off I - 217 V2LNAw W I - 208 V2LNAwSOw W W - 212 V2LNAwSOs W S - 181 V2LNAwSHWw W W - 244 V2LNAwGR W I +9% 237 V3 351 ± 44GtC NADW, AABW, SO XP, CT V3L S I - 313 V3LNAoff Off I - 357 V3LNAw W I - 346 V3LNAwSOw W W - 369 V3LNAwSHWw W W - 392 V3LNAwSOwSHWw W W - 426 V3LSOs S S - 289 V3LNAwSOs I S - 320 V3LNAwGR W I +9% 357 V3LNAwGRSOs I S +9% 343 V 4, 567 ± 39GtC V4LNAw W S - 514 V4LNAwSHWw W W - 605 V4LNAwSOwSHWw W W - 609 V4LNAwSOs I S - 534 V4LNAwGR W I +9% 574 Table 1. Main characteristics of LGM experiments. CT indicates the difference between the late Holocene and LGM terrestrial carbon stock (GtC) for all the experiments performed and calculated following Equation 3. The mean CT and standard deviation for each set of experiments (V1-V4) is also shown. The relative formation rates of NADW and AABW are indicated as follows: for NADW, S=Strong (>= 20 Sv), I=Intermediate (15-20 Sv), W=Weak (10-15 Sv) or Off= shutdown (2-3 Sv); for the AABW transport in the Indo-Pacific basin, S=Strong (10-16 Sv), I=Intermediate (8-10 Sv) and W=Weak (<= 7 Sv). All symbols are filled except experiments in which export production (SO XP) was enhanced by 9% over the Southern Ocean (56-36S) compared to the pre-industrial control run. Contact: l.menviel@unsw.edu.au for any question on the dataset content and provenance paola.petrelli@utas.edu.au for questions or issues with file accessibility from THREDDS server. NCDC-Paleoclimatology https://www.ncdc.noaa.gov/data-access/paleoclimatology-data - Bauer Bruce Investigator : Menviel, L. 2017-10-18 ONLINE Files online, ASCII https://www.ncdc.noaa.gov/paleo/study/22850 https://www1.ncdc.noaa.gov/pub/data/paleo/gcmoutput/menviel2016/ https://www1.ncdc.noaa.gov/pub/data/paleo/gcmoutput/menviel2016/menviel2017-loveclim.txt http://dx.doi.org/10.4225/41/58192cb8bff06 https://www1.ncdc.noaa.gov/pub/data/paleo/gcmoutput/menviel2016/ https://www1.ncdc.noaa.gov/pub/data/paleo/gcmoutput/menviel2016/menviel2017-loveclim.txt http://dx.doi.org/10.4225/41/58192cb8bff06 English https://www.ncdc.noaa.gov/paleo/study/22850 https://www1.ncdc.noaa.gov/pub/data/paleo/gcmoutput/menviel2016/ https://www1.ncdc.noaa.gov/pub/data/paleo/gcmoutput/menviel2016/menviel2017-loveclim.txt http://dx.doi.org/10.4225/41/58192cb8bff06 Menviel, L., J. Yu, F. Joos, A. Mouchet, K.J. Meissner, and M.H. England2017Poorly ventilated deep ocean at the Last Glacial Maximum inferred from carbon isotopes: a data-model comparison studyPaleoceanography322-1710.1002/2016PA003024http://onlinelibrary.wiley.com/doi/10.1002/2016PA003024/abstract;jsessionid=C5562158ADD0E948C4CE653BFA845A5B.f03t04 START YEAR: 21000 cal yr BP * END YEAR: 18000 cal yr BP -180 -90 180 90