UVIC2-8, IFM

The model used is the University of Victoria (UVic) Earth System Climate Model (Weaver et al 2001) in the standard Redfield configuration described by Oschilies et al (2008). The oceanic component is a fully three-dimensional primitive-equation model with nineteen levels in the vertical ranging from 50 m thickness near the surface to 500m in the deep ocean. It contains a simple marine ecosystem model with the two major nutrients nitrate and phosphate and two phytoplankton classes, nitrogen fixers and other phytoplankton, with the former being limited only by phosphate. detritus sinks with a sinking velocity increasing linearly with depth from 7 m/day at the surface to 40 m/day at 1000 m depth and constant below. The ocean component is coupled to a single-level energy-moisture balance model of the atmosphere, a dynamic-thermodynamic sea ice component, and a terrestrial vegetation and carbon cycle component. All model components use a common horizontal resolution of 1.8 × 3.6 degrees.

Diapycnal mixing is parametrized as the sum of tidally induced mixing (Simmons et al 2004) and background mixing of 0.15 cm²/s, and an additional Southern Ocean enhancement of the vertical diffusivity by 1.0 cm²/s. The tidally induced diffusivity rapidly decays in the water column above the seafloor with an exponential vertical scale of 500 m, so that in most parts of the thermocline diapycnal mixing is determined by the background diffusivity.

The model was spun up for more than 10,000 years under pre-industrial atmospheric and astronomical boundary conditions and subsequently run under historical conditions from year 1765 to 2000 using fossil-fuel and land-use carbon emissions. Following the IPCC AR4 protocol, we switch to emissions according to the SRES A2 (Nakicenovic et al. 2000) scenario in year 2000.