Abstract We herein present the CLIMBER-3a Earth System Model of Intermediate Complexity (EMIC)

• Main Authors: Marisa Montoya, Æ Alexa Griesel, Æ Anders Levermann, Juliette Mignot, Æ Matthias Hofmann, Andrey Ganopolski, Æ Stefan Rahmstorf
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Published: 2004
• Subjects: Sea ice
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.693.9718; http://www.pik-potsdam.de/%7Estefan/Publications/Journals/montoya_etal_climdyn_2005.pdf

main difference with respect to CLIMBER-2 is its oce-anic component, which has been replaced by a state-of-the-art ocean model, which includes an ocean general circulation model (GCM), a biogeochemistry module, and a state-of-the-art sea-ice model. Thus, CLIMBER-3a includes modules describing the atmosphere, land-surface scheme, terrestrial vegetation, ocean, sea ice, and ocean biogeochemistry. Owing to its relatively simple atmospheric component, it is approximately two orders of magnitude faster than coupled GCMs, allowing the performance of a much larger number of integrations and sensitivity studies as well as longer ones. At the same time its oceanic component confers on it a larger degree of realism compared to those EMICs which in-clude simpler oceanic components. The coupling does not include heat or freshwater flux corrections. The comparison against the climatologies shows that CLIMBER-3a satisfactorily describes the large-scale characteristics of the atmosphere, ocean and sea ice on seasonal timescales. As a result of the tracer advection scheme employed, the ocean component satisfactorily simulates the large-scale oceanic circulation with very little numerical and explicit vertical diffusion. The model is thus suited for the study of the large-scale climate and large-scale ocean dynamics. We herein describe its per-formance for present-day boundary conditions. In a companion paper (Part II), the sensitivity of the model to variations in the external forcing, as well as the role of certain model parameterisations and internal parame-ters, will be analysed. 1