North Altantic meltwater pulse experiment using a coupled atmosphere-ocean-sea ice-carbon cycle model (LOVECLIM).

Atmospheric (ECBilt), sea ice-ocean (CLIO), terrestrial vegetation (VECODE) components of the coupled atmosphere-ocean-sea ice-carbon cycle model LOVECLIM results

The atmospheric component of the coupled model LOVECLIM is ECBilt [Opsteegh et al., 1998], a spectral T21, three-level model, based on quasi-geostrophic equations extended by estimates of the neglected ageostrophic terms [Lim et al., 1991] in order to close the equations at the equator. The model contains a full hydrological cycle which is closed over land by a bucket model for soil moisture. Synoptic variability associated with weather patterns is explicitly computed. Diabatic heating due to radiative fluxes, the release of latent heat and the exchange of sensible heat with the surface are parametrized. Compared to the standard version of LOVECLIM we enhanced the sensitivity of ECBilt to longwave radiation forcing by a factor of 2 [Timm and Timmermann, 2007].

The sea ice-ocean component of LOVECLIM, CLIO [Goosse et al., 1999; Goosse and Fichefet, 1999; Campin and Goosse, 1999] consists of a free-surface primitive equation model with 3° x3° resolution coupled to a thermodynamic-dynamic sea ice model. Coupling between atmosphere and ocean is done via the exchange of freshwater and heat fluxes, rather than by virtual salt fluxes. To avoid a singularity at the North Pole, the oceanic component makes use of two subgrids: The first one is based on classic longitude and latitude coordinates and covers the whole ocean except for the North Atlantic and Arctic Ocean. These are covered by the second spherical subgrid, which is rotated and has its poles at the equator in the Pacific (111°W) and Indian Ocean (69°E).

The terrestrial vegetation module of LOVECLIM, VECODE, described in Brovkin et al. [1997], has recently been coupled to the LOVECLIM model [Renssen et al., 2005]. Based on annual mean values of several climatic variables, the VECODE model computes the evolution of the vegetation cover described as a fractional distribution of desert, tree, and grass in each land grid cell once a year. Within LOVECLIM, simulated vegetation changes affect only the land-surface albedo, and have no influence on other processes, e.g., evapo-transpiration. VECODE does not simulate plant types that are specific for the Arctic region (dwarf shrubs, forbs, mosses etc.), but uses a bulk approach of representing vegetation cover as a mixture of trees.

LOCH is a 3-dimensional global model of the oceanic carbon cycle. A first version of the model was described by Mouchet and Francois [1996]. The state variables considered in the model are the dissolved inorganic carbon (DIC), total alkalinity, phosphates (PO3-4), organic products, oxygen and silica. LOCH is fully coupled to CLIO, with the same time step. In addition to their biogeochemical transformations tracers in LOCH fully experience the circulation field predicted by CLIO. LOCH computes the export production from the fate of a phytoplankton pool in the euphotic zone (0-120 m). The phytoplankton growth depends on the availability of nutrients (PO3- 4) and light, with a weak temperature dependence.

Further information can be found in Menviel et al (2008).

Atm. variables: temperature [C], precipitation [cm/yr], snow fall[ cm/yr], evaporation[ cm/yr], E-P [cm/yr], heat flux [W/m^2], solar & thermal radiation [W/m^2], surface & planetary albedo [%], bottom moisture [m], snow depth over land [m], sea ice thickness [m], surface runoff over land and ocean [cm/yr], specific and relative humidity [kg/kg], total cloud cover, wind [m/s], stream function [m^2/s], velocity potential [m^2/s], quasi-geostrophic potential vorticity [1/s], geopotential height [m^2/s^2]
Ocean variables: velocity [m/s], temperature [K], salinity, ice thickness [m], lead fraction [%], oceanic flux at the ice base [cm/yr], ice velocity [m/s], SST, SSS, ocean velocity [0-100m] [m/s], thickness of convective layer [m], total heat flux at ocean surface [W/m^2], freshwater flux at ocean surface [cm/yr]
Geochemical variables: DIC, alkalinity, phosphates, dissolved oxygen, silicates, marine export production
Terrestrial vegetation variables: fraction of tree, fraction of grass, fraction of desert, fraction of needle, leaf area index for tree, leaf area index for grass, albedo, annual temperature, growing degree days above 0, precipitation, carbon uptake, carbon stock, leaves phytomass (b1), stems and roots biomass (b2), litter (b3), mortmass and soil organic matter (b4), new primary production, icesheet fraction
ZonalGlobal by varies
MeridionalGlobal by varies
VerticalSurface; air temperature: 100, 350, 650, 1000 millibar; u, v, psi, chi, qgpv, geopg: 200, 500, 800 millibar; ocean t, s, u, v: 5126.18,4385.22, 3661.11, 2963.25, 2307.36, 1717.9, 1225.11, 850.19, 588.88, 415.07, 299.26, 219.86, 163.28, 121.52, 89.75, 64.96, 45.2, 29.17, 15.98, 5 meters  
Temporalpre-industrial conditions, 1000yrs long experiment. atm: annual means; ocn: annual/monthly means; geochem: annual means, every 100 yrs; terrestrial vegetation annual means
Volume9.4GB (annual mean atmospheric + upper ocean)
Server public:
SourceMenviel et al (2008) 
AcquiredFeb 13, 2009
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