Sea salt as an ice core proxy for past sea ice extent: A process‐based model study

Abstract

Sea ice is a reflection of, and a feedback on, the Earth's climate. We explore here, using a global atmospheric chemistry-transport model, the use of sea salt in Antarctic ice cores to obtain continuous long-term, regionally integrated records of past sea ice extent, synchronous with ice core records of climate. The model includes the production, transport, and deposition of sea salt aerosol from the open ocean and "blowing snow" on sea ice. Under current climate conditions, we find that meteorology, not sea ice extent, is the dominant control on the atmospheric concentration of sea salt reaching coastal and continental Antarctic sites on interannual timescales. However, through a series of idealized sensitivity experiments, we demonstrate that sea salt has potential as a proxy for larger changes in sea ice extent (e.g., glacial-interglacial). Treating much of the sea ice under glacial conditions as a source of salty blowing snow, we demonstrate that the increase in sea ice extent alone (without changing the meteorology) could drive, for instance, a 68% increase in atmospheric sea salt concentration at the site of the Dome C ice core, which exhibits an approximate twofold glacial increase in sea salt flux. We also show how the sensitivity of this potential proxy decreases toward glacial sea ice extent-the basis of an explanation previously proposed for the lag observed between changes in sea salt flux and δD (an ice core proxy for air temperature) at glacial terminations. The data thereby permit simultaneous changes in sea ice extent and climate.

Year-round records of bulk and size-segregated aerosol composition in central Antarctica (Concordia site) – Part 1: Fractionation of sea-salt particles

“…11b) or 28 August to 11 September 2009 (Fig. 11c) , that includes open-ocean and blowing-snow sources was developed by Levine et al (2014) to simulate sea-salt levels in Antarctica. Tested against atmospheric sea-salt observations, the model confirmed the importance of sea-ice-related seasalt emissions in winter at both coastal and central Antarctica.…”

Cyclone-induced surface ozone and HDO depletion in the Arctic

“…A detailed process-based SSA scheme has been implemented in the model (Levine et al, 2014) based on the work of Reader and McFarlane (2003). Since the Levine et al (2014) work, some updates have been introduced to the model, including improved precipitation, dry deposition velocities on snow for inorganic bromine species, and reduced snow salinity applied to the blowing snow (Legrand et al, 2016).…”

“…Since the Levine et al (2014) work, some updates have been introduced to the model, including improved precipitation, dry deposition velocities on snow for inorganic bromine species, and reduced snow salinity applied to the blowing snow (Legrand et al, 2016). Both open-ocean-sourced and sea-ice-sourced SSA (OO-SSA and SI-SSA) are tagged in order to track their history.…”

Century‐scale perspectives on observed and simulated Southern Ocean sea ice trends from proxy reconstructions

“…Sea salt in ice cores has been used a qualitative indicator for Antarctic SIE over glacial and interglacial timescales, but does not appear to capture multidecadal and shorter timescale variability that is important for change detection on anthropogenic timescales [Abram et al, 2013;Levine et al, 2014]. MSA records exist for other ice cores, but MSA is a difficult chemical marker to extract from ice cores that requires careful treatment of the ice [Abram et al, 2008], and does not reliably represent sea ice change at all sites [Abram et al, 2007[Abram et al, , 2013.…”