Sea Ice Versus Storms: What Controls Sea Salt in Arctic Ice Cores?

• Published in: Geophysical research letters Vol. 45; no. 11; pp. 5572 - 5580
• Main Authors: Rhodes, Rachael H., Yang, Xin, Wolff, Eric W.
• Format: Journal Article
• Language: English
• Published: Washington John Wiley & Sons, Inc 16.06.2018
• Subjects: Aerosol effects; Aerosol transport; Aerosols; Arctic; Arctic ice; Arctic sea ice; Chemical transport; chemical transport model; Coastal environments; Computer simulation; Cores; Deposition; Emission; Holocene; Ice; ice core; Ice cores; Ice environments; Mathematical models; Meteorology; Numerical models; Organic chemistry; Polar environments; Polar regions; Records; Salts; Satellites; Sea ice; sea ice proxy; sea salt aerosol; Seasonal variations; Seasonality; Sodium; Storms; Temperature; Tracers; Transport; Variability; Arctic region; Greenland
• ISSN: 0094-8276; 1944-8007
• DOI: 10.1029/2018GL077403

The sea ice surface is thought to be a major source of sea salt aerosol, suggesting that sodium records of polar ice cores may trace past sea ice extent. Here we test this possibility for the Arctic, using a chemical transport model to simulate aerosol emission, transport, and deposition in the satellite era. Our simulations suggest that sodium records from inland Greenland ice cores are strongly influenced by the impact of meteorology on aerosol transport and deposition. In contrast, sodium in coastal Arctic cores is predominantly sourced from the sea ice surface and the strength of these aerosol emissions controls the ice core sodium variability. Such ice cores may therefore record decadal to centennial scale Holocene sea ice changes. However, any relationship between ice core sodium and sea ice change may depend on how sea ice seasonality impacts sea salt emissions. Field‐based observations are urgently required to constrain this. Plain Language Summary To better understand the variability of Arctic sea ice and its interaction with climate, we need to reconstruct its history back beyond the time range of observations. As the sea ice surface is a major source of sea salt aerosol in the polar regions, one possibility is to use sea salt sodium records in Arctic ice cores as tracers of sea ice change. However, there are other factors that influence ice core sodium, in addition to the strength of the sea ice source of aerosol. The most important is meteorology, or storminess, that impacts how aerosol is transported and deposited. We adopt a new approach to tackling this problem, using a numerical model that replicates the emission, transport, and deposition of sea salt to simulate Arctic ice core sodium records. This is used to investigate the competing controls of sea ice versus storminess. Our results suggest that sodium records of coastal Arctic ice cores, away from central Greenland, offer the greatest potential for Holocene sea ice reconstruction. However, this study also highlights the need for more field observations to improve understanding of aerosol emission over the sea ice. Key Points Simulated satellite-era interannual variability in Greenland ice core sodium concentrations is driven by meteorology not sea ice Sodium budget of coastal Arctic ice cores is dominated by sea salt from the sea ice surface not the open ocean Interannual variability of sodium records from coastal Arctic cores is driven by aerosol emission strength, not transport or deposition