High resolution arctic iodine variability since the last glacial termination

Abstract

Tropospheric iodine plays a key role in ozone depletion and new particle formation. Understanding how iodine responds to climatic shifts is crucial for predicting future atmospheric composition. Here, we present high-resolution iodine fluxes in the EGRIP (East GReenland Ice Core Project) ice core in central Greenland spanning the last 15.7 kyr. By integrating these data with complementary proxies from other ice and marine sediment cores, we explore both the temporal and spatial patterns of iodine deposition across the Greenland ice sheet. We find lower iodine fluxes at EGRIP compared to RECAP and NEEM ice cores over the last 15.7 kyr, explained by the lower efficiency of iodine transport to the interior of the ice sheet. Our results show that during the cold periods of the Last Glacial Termination (15.7–11.7 kyr before present), iodine fluxes at EGRIP were higher than during the Holocene, likely due to enhanced long-range transport of iodine adsorbed onto dust and sea-salt aerosols under stronger glacial wind regimes. In contrast, during the Holocene, the sources and transport pathways of iodine shifted to marine sources. We infer that iodine was increasingly emitted from the expanded seasonal sea ice area and biologically active subpolar North Atlantic waters, though overall fluxes at EGRIP were lower than during the glacial period, reflecting the reduction in long-range transport. After rising until 5 kyr before present, iodine fluxes declined throughout the Neoglacial, in concomitance with regional cooling, increased sea ice extent, and reduced ocean productivity.