DOI: 10.25921/a136-zc04
title: NOAA/WDS Paleoclimatology - LOVECLIM Earth System Model Last Glacial Maximum oceanic d13C and D14C data

description: 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.
description: 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.