The hydrologic cycle and atmospheric rivers in CESM2 simulations of the Last Glacial Maximum

This dataset contains processed output from CESM2 simulations presented in the GRL manuscript "The hydrologic cycle and atmospheric rivers in CESM2 simulations of the Last Glacial Maximum.'' The files, in netCDF format, include processed integrated vapor transport (IVT), precipitation, and detected atmospheric river (AR) frequency and associated fields (AR precipitation, AR IVT, and AR extreme precipitation) from three simulations: a pre-industrial (PI) control, a full Last Glacial Maximum (LGM) run, and a run with LGM ice sheets but otherwise similar to the PI one. These are further described in the paper, but in all cases comprise 100 simulated years with the same resolution. In all cases, the output from the three simulations is stored for each variable with the "experiment" axis. For IVT, "uIVT" and "vIVT" refer to the zonal and meridional components, while "IVT" refers to magnitude; "divIVT" is the divergence of IVT. For variables involving precipitation, "pr99" refers to the 99th percentile precipitation. For ARs, "AR" refers to AR frequency and "frac_prec99" refers to the fraction of extreme precipitation associated with ARs. "diff_ttest_pval" contains p-value of relevant two-sided t-tests.

Associated article abstract:

Proxy reconstructions and model simulations of precipitation during Earth's glacial periods suggest that the locations and mechanisms of atmospheric moisture transport have changed considerably during Earth's past. We investigate the hydroclimate of the Last Glacial Maximum (LGM) using simulations with the Community Earth System Model, with a focus on the extratropics and the influence of atmospheric rivers (ARs), a key driver of modern-day moisture transport globally. Mean and extreme precipitation increase significantly over southwestern Patagonia, Iberia, and southwestern North America—mid-latitude regions affected by ARs in the modern climate—despite overall decreases elsewhere. In each, the associated moisture transport changes are different, with increased transport and AR activity mainly occurring in the North Atlantic. The overall LGM response is dominated by the response to ice sheets, with other forcings causing additional cooling and drying over the extratropics and a strong decrease of moisture transport over the subpolar North Atlantic.