Sea‐salt aerosol distribution during the Last Glacial Maximum and its implications for mineral dust

Sea‐salt aerosols and mineral dust in ice cores are complementary in their use as indicators of past climate because of their differing dependence on the various factors affecting their deposition rates, such as winds, precipitation, and soil properties. Here sea‐salt aerosol distributions for the Last Glacial Maximum (LGM) and for the modern climate are simulated using an online passive aerosol model in the Canadian Centre for Climate Modelling and Analysis second‐generation general circulation model. Comparison of simulated deposition rates of sea salt from the open ocean with polar ice core concentrations indicates that a 75‐fold enhancement, beyond that indicated by the model, is necessary for consistency with the Greenland ice core observations and an approximate tenfold additional enhancement is necessary for Antarctica. However, considering sea ice as a possible sea‐salt aerosol source allows greater simulated LGM deposition in Greenland, though there is a great deal of uncertainty in the possible magnitude of this. Using very simple models for which 1–2% of the total modern sea‐salt aerosol comes from ice‐covered areas, the ice core data can be accommodated by a sevenfold to tenfold overall additional LGM source enhancement. The fact that these additional enhancement factors are similar to the enhancement factor previously determined for mineral dust using the same general circulation model suggests that some combination of increased LGM surface winds and transport or deposition to ice core locations is necessary for agreement with the ice core data.