Reconstructing Holocene conditions under the McMurdo Ice Shelf using Antarctic barnacle shells

Cycles of δ18O observed within each sample sometimes correlate with the external growth ridges, but not always, and have amplitudes of typically 0.6‰. This magnitude of variation suggests shell growth during a significant portion of the year, although it remains unclear whether growth continues throughout the year. However, the prominent growth bands suggest at least a signficant seasonal slowing in growth rate. Variations in barnacle δ18O within each plate and between plates are too large to be caused by temperature, and instead reflect changes in δ18O of the seawater, allowing some assessment of seawater salinity under the ice shelf. Salinities are lowered by addition of meltwaters, but the barnacle δ18O data suggest values do not go below 33‰. These data indicate that Bathylasma has potential as an archive of paleoclimate information for shallow/intermediate water depths and, in particular, for difficult to reach environments such as below ice-shelves of Antarctica.