Sea level pressure variability over the southern Indian Ocean inferred from a glaciochemical record in Princess Elizabeth Land, east Antarctica

Abstract

A 250‐year, high‐resolution, multivariate ice core record from LGB65 (70°50′07″S, 77°04′29″E; 1850 m asl), Princess Elizabeth Land (PEL), is used to investigate sea level pressure (SLP) variability over the southern Indian Ocean (SIO). Empirical orthogonal function (EOF) analysis reveals that the first EOF (EOF1) of the glaciochemical record from LGB65 represents most of the variability in sea salt throughout the 250‐year record. EOF1 is negatively correlated (95% confidence level and higher) to instrumental mean sea level pressure (MSLP) at Kerguelen and New Amsterdam islands, SIO. On the basis of comparison with NCEP/NCAR reanalysis, strong correlations were found between sea‐salt variations and a quasi‐stationary low that lies to the north of Prydz Bay, SIO. Comparison with a 250‐year‐long summer transpolar index (STPI) inferred from sub‐Antarctic tree ring records reveals strong coherency. Decadal‐scale SLP variability over SIO suggests shifting of the polar vortex. Prominent decadal‐scale deepening of the southern Indian Ocean low (SIOL) exists circa 1790, 1810, 1835, 1860, 1880, 1900, and 1940 A.D., continuously after the 1970s, and prominent weakening circa 1750, 1795, 1825, 1850, 1870, 1890, 1910, and 1955 A.D. The LGB65 sea‐salt record is characterized by significant decadal‐scale variability with a strong ∼21‐year periodic structure (99.9% confidence level). The relationship between LGB65 sea salt and solar irradiance changes shows that this periodicity is possibly the solar Hale cycle (22 years).