GC21E-0985 – Uncertainty in Earth System Models: Benchmarks for Ocean Model Performance and Validation


Oluwaseun O. Ogunro
Oak Ridge National Laboratory
Scott Elliott
Los Alamos National Laboratory
Nathan Collier
Oak Ridge National Laboratory
Oliver W. Wingenter
New Mexico Tech
Clara Deal
University of Alaska Fairbanks
Weiwei Fu
University of California Irvine
Forrest M. Hoffman (forrest at climatemodeling dot org)
Oak Ridge National Laboratory


Interpretation and Uncertainty in Climate, Earth System, Integrated Assessment, and Impact Models and Observations II Posters
Tuesday, December 12, 2017 08:00–12:20
New Orleans Ernest N. Morial Convention Center – Poster Hall D–F


The mean ocean CO2 sink is a major component of the global carbon budget, with marine reservoirs holding about fifty times more carbon than the atmosphere. Phytoplankton play a significant role in the net carbon sink through photosynthesis and drawdown, such that about a quarter of anthropogenic CO2 emissions end up in the ocean. Biology greatly increases the efficiency of marine environments in CO2 uptake and ultimately reduces the impact of the persistent rise in atmospheric concentrations. However, a number of challenges remain in appropriate representation of marine biogeochemical processes in Earth System Models (ESM). These threaten to undermine the community effort to quantify seasonal to multidecadal variability in ocean uptake of atmospheric CO2.

In a bid to improve analyses of marine contributions to climate–carbon cycle feedbacks, we have developed new analysis methods and biogeochemistry metrics as part of the International Ocean Model Benchmarking (IOMB) effort. Our intent is to meet the growing diagnostic and benchmarking needs of ocean biogeochemistry models. The resulting software package has been employed to validate DOE ocean biogeochemistry results by comparison with observational datasets. Several other international ocean models contributing results to the fifth phase of the Coupled Model Intercomparison Project (CMIP5) were analyzed simultaneously.

Our comparisons suggest that the biogeochemical processes determining CO2 entry into the global ocean are not well represented in most ESMs. Polar regions continue to show notable biases in many critical biogeochemical and physical oceanographic variables. Some of these disparities could have first order impacts on the conversion of atmospheric CO2 to organic carbon. In addition, single forcing simulations show that the current ocean state can be partly explained by the uptake of anthropogenic emissions. Combined effects of two or more of these forcings on ocean biogeochemical cycles and ecosystems are challenging to predict since additive or antagonistic effects may occur. A benchmarking tool for accurate assessment and validation of marine biogeochemical outputs will be indispensable as the model community continues to improve ESM developments. It will provide a first order tool in understanding climate–carbon cycle feedbacks.

Forrest M. Hoffman (forrest at climatemodeling dot org)