The Max-Planck-Institute global ocean/sea ice model with orthogonal curvilinear coordinates

Abstract

The Hamburg Ocean Primitive Equation model has undergone significant development in recent years. Most notable is the treatment of horizontal discretisation which has undergone transition from a staggered E-grid to an orthogonal curvilinear C-grid. The treatment of subgridscale mixing has been improved by the inclusion of a new formulation of bottom boundary layer (BBL) slope convection, an isopycnal diffusion scheme, and a Gent and McWilliams style eddy-induced mixing parameterisation. The model setup described here has a north pole over Greenland and a south pole on the coast of the Weddell Sea. This gives relatively high resolution in the sinking regions associated with the thermohaline circulation. Results are presented from a 450 year climatologically forced integration. The forcing is a product of the German Ocean Model Intercomparison Project and is derived from the European Centre for Medium Range Weather Forecasting reanalysis. The main emphasis is on the model's representation of key quantities that are easily associated with the ocean's role in the global climate system. The global and Atlantic northward poleward heat transports have peaks of 1.43 and 0.84 PW, at 18degrees and 21degrees N respectively. The Atlantic meridional overturning streamfunction has a peak of 15.7 Sv in the North Atlantic and an outflow of 11.9 Sv at 30degrees S. Comparison with a simulation excluding BBL shows that the scheme is responsible for up to a 25% increase in North Atlantic heat transport, with significant improvement of the depths of convection in the Greenland, Labrador and Irminger Seas. Despite the improvements, comparison with observations shows the heat transport still to be too weak. Other outstanding problems include an incorrect Gulf Stream pathway, a too strong Antarctic Circumpolar Current, and a too weak renewal of Antarctic Intermediate Water. Nevertheless, the model has been coupled to the atmospheric GCM ECHAM5 and run successfully for over 250 years without any surface flux corrections. (C) 2002 Elsevier Science Ltd. All rights reserved

Solar forcing as an important trigger for West Greenland sea-ice variability over the last millennium

“…The model configuration included the atmosphere component ECHAM5 (Roeckner et al, 2003) at T31 resolution (~3.75 ) with 19 vertical layers, complemented by a land-surface scheme including dynamical vegetation (JSBACH) (Brovkin et al, 2009). The ocean component MPI-OM (Marsland et al, 2003), including the dynamics of sea ice formulated using viscous-plastic rheology (Hibler, 1979), has an average horizontal resolution of 3 Â 1.8 with 40 uneven vertical layers. The climate model was previously utilized to analyse the climate of the last millennium (Jungclaus et al, 2010), the last glacial (Zhang et al, , 2014 and the last interglacial period (Varma et al, 2012;, as well as warm climates of the Miocene (Knorr et al, 2011;Knorr and Lohmann, 2014) and the Pliocene (Stepanek and Lohmann, 2012;Dowsett et al, 2013).…”

Modelling the Overflows Across the Greenland–Scotland Ridge

“…There are two different approaches to achieve this goal. One relatively simple 'plumbing' approach is to reduce the spurious mixing by connecting grid cells above and below a topographic step (Beckmann and Döscher 1997;Campin and Goosse 1999;Marsland et al 2003). In the latter scheme for example (see Marsland et al 2003, their Fig.…”

“…The atmospheric part of the model, ECHAM5 (Roeckner et al 2003), has a horizontal resolution of 1.875° by 1.875° (T63) and 31 vertical levels. The ocean/sea ice part of the model, MPIOM (Marsland et al 2003), has a 1.5° by 1.5° horizontal resolution on a curvilinear grid with 40 vertical levels. MPIOM uses a curvilinear orthogonal grid and the two grid poles are placed upon Antarctica and Greenland thus avoiding the pole-singularity problem at the North Pole and providing relatively high resolution in the deep-water formation regions of the Labrador Sea and the Greenland Sea (see Jungclaus et al 2006a, their Fig.…”

“…In MPIOM, a slope convection parameterization was implemented and Marsland et al (2003) showed that the scheme improved the near bottom water mass characteristics to the south of the GSR even though a vertical grid resolution of 100-300 m at 2,000 m depth does not allow for a 'realistic' vertical structure of the plume. Furthermore, the horizontal resolution is far too coarse to allow horizontal eddies with a radius of about 50-100 km to develop (Jiang and Garwood 1996;Jungclaus et al 2001).…”

Using altimetry to help explain patchy changes in hydrographic carbon measurements

“…[61] MPIOM-HAMOCC5 is the MPI ocean model (MPI-OM) [Marsland et al, 2003] and the Hamburg oceanic carbon cycle model HAMOCC5, and was presented in the study of Wetzel et al [2005]. This model was also forced with NCEP-1 reanalysis fluxes, and bulk formulas were used to calculate surface buoyancy fluxes.…”