Bibliography - I. Held

1. Galbraith, E. D., E. Y. Kwon, A. Gnanadesikan, K. B. Rodgers, Stephen M. Griffies, D. Bianchi, Jorge Sarmiento, J. P. Dunne, J. Simeon, R. D. Slater, Andrew T. Wittenberg, and I. Held, 2011: Climate Variability and Radiocarbon in the CM2Mc Earth System Model. Journal of Climate, American Meteorological Society, doi:10.1175/2011JCLI3919.1
   [ Abstract ]

   The distribution of radiocarbon (¹⁴C) in the ocean and atmosphere has fluctuated on timescales ranging from seasons to millennia. It is thought that these fluctuations partly reflect variability in the climate system, offering a rich potential source of information to help understand mechanisms of past climate change. Here, a long simulation with a new, coupled model is used to explore the mechanisms that redistribute ¹⁴C within the Earth system on inter-annual to centennial timescales. The model, CM2Mc, is a lower-resolution version of the Geophysical Fluid Dynamics Laboratory's CM2M model, uses no flux adjustments, and incorporates a simple prognostic ocean biogeochemistry model including ¹⁴C. The atmospheric ¹⁴C and radiative boundary conditions are held constant, so that the oceanic distribution of ¹⁴C is only a function of internal climate variability. The simulation displays previously-described relationships between tropical sea surface ¹⁴C and the model-equivalents of the El Niño Southern Oscillation and Indonesian Throughflow. Sea surface ¹⁴C variability also arises from fluctuations in the circulations of the subarctic Pacific and Southern Ocean, including North Pacific decadal variability, and episodic ventilation events in the Weddell Sea that are reminiscent of the Weddell Polynya of 1974-1976. Interannual variability in the air-sea balance of ¹⁴C is dominated by exchange within the belt of intense Southern Westerly winds, rather than at the convective locations where the surface ¹⁴C is most variable. Despite significant interannual variability, the simulated impact on air-sea exchange is an order of magnitude smaller than the recorded atmospheric ¹⁴C variability of the past millennium. This result partly reflects the importance of variability in the production rate of ¹⁴C in determining atmospheric ¹⁴C, but may also reflect an underestimate of natural climate variability, particularly in the Southern Westerly winds.

2. Balaji, V., J. Anderson, I. Held, M. Winton, J. Durachta, S. Malyshev, and R. J. Stouffer, May 2005: The Exchange Grid: a mechanism for data exchange between Earth System components on independent grids. Parallel Computational Fluid Dynamics 2005 - Theory and Applications, Elsevier, http://www.gfdl.noaa.gov/~vb/pdf/xgridpaper.pdf, 179-188
   [ Abstract ]

   We present a mechanism for exchange of quantities between components of a coupled Earth system model, where each component is independently discretized. The exchange grid is formed by overlaying two grids, such that each exchange grid cell has a unique parent cell on each of its antecedent grids. In Earth System models in particular, processes occurring near component surfaces require special surface boundary layer physical processes to be represented on the exchange grid. The exchange grid is thus more than just a stage in a sequence of regridding between component grids. We present the design and use of a 2-dimensional exchange grid on a horizontal planetary surface in the GFDL Flexible Modeling System (FMS), highlighting issues of parallelism and performance.

Direct link to page: http://cmi.princeton.edu/bibliography/results.php?author=3940