Mineral Dust Influence on the Glacial Nitrate Record from the RICE Ice Core, West Antarctica and Environmental Implications

• Main Authors: Venugopal, Abhijith U., Bertler, Nancy A. N., Pyne, Rebecca L., Kjær, Helle A., Winton, V. Holly L., Mayewski, Paul A., Cortese, Giuseppe
• Format: Text
• Language: English
• Published: 2020
• Subjects: geo; envir; Antarctic; Dome Fuji; Roosevelt Island; Southern Ocean; The Antarctic; West Antarctica; Antarc*; Antarctica; EPICA; ice core
• Online Access: https://doi.org/10.5194/cp-2020-151; https://cp.copernicus.org/preprints/cp-2020-151/

Nitrate (NO3−), an abundant aerosol in polar snow, is a complex environmental proxy to interpret owing to the variety of its sources and its susceptibility to post-depositional processes. During the last glacial period, when the dust level in the Antarctic atmosphere was higher than today by a factor up to ~25, mineral dust appears to have a stabilizing effect on the NO3− concentration. However, the exact mechanism remains unclear. Here, we present new and highly resolved records of NO3− and non-sea salt calcium (nssCa2+, a proxy for mineral dust) from the Roosevelt Island Climate Evolution (RICE) ice core for the period 26–40 kilo years Before Present (ka BP). This interval includes seven millennial-scale Antarctic Isotope Maxima (AIM) events, against the background of a glacial climate state. We observe a significant correlation between NO3− and nssCa2+ over this period and especially during AIM events. We put our observation into a spatial context by comparing the records to existing data from east Antarctic cores of EPICA Dome C (EDC), Vostok and central Dome Fuji. The data suggest that nssCa2+ is contributing to the effective scavenging of NO3− from the atmosphere through the formation of Ca(NO3)2. The geographic pattern implies that the process of Ca(NO3)2 formation occurs during the long-distance transport of mineral dust from the mid-latitude source regions by Southern Hemisphere Westerly Winds (SHWW) and most likely over the Southern Ocean. Since NO3− is dust-bound and the level of dust mobilized through AIM events is mainly regulated by the latitudinal position of SHWW, we suggest that NO3− may also have the potential to provide insights into paleo-westerly wind pattern during the events.