Paper No. 37-11
Presentation Time: 4:50 PM
HOLOCENE PARTICLE-SIZE-DISTRIBUTION (PSD) FROM SOUTH POLE ICE CORE (SPICECORE)
The Southern Hemisphere Westerly Winds (SHWW) are a major component of the global climate system, affecting moisture and heat transport, cryosphere dynamics, and the exchange of carbon between the ocean and atmosphere. Recent work has shown that the SHWW respond dynamically to temperature forcing on a range of timescales and can shift latitudinally in a zonally-symmetric manner. Meridional shifts in the SHWW coincide with local changes in wind strength; for instance, southward-shifted SHWW intensify wind strengths near Antarctica. Because particle-size-distributions (PSD) of dust aerosols reflect the strength of aeolian transport (assuming dust sources do not change) ice core dust PSD can be used as a proxy for past SHWW behavior. We present a new annually resolved Holocene record of dust PSD from the South Pole ice core (SPICEcore). The SPICEcore was drilled during the 2014-2016 seasons, reaching a depth of 1751m (~54 ka). Sticks (3x3x100 cm) of the ice core were melted and analyzed using a continuous flow analysis system at Dartmouth College. Insoluble particles (1.0 to 12.0 µm diameter) were analyzed using an Abakus laser particle detector. We calculate the mode value of the volume PSD (dV/dlnd) and use this parameter to reconstruct past latitudinal shifts of the SHWW. Using NCEP/NCAR V1 reanalysis to calibrate the dust record (1948-1998), we find a negative correlation with SHWW (r = -0.31-0.34, p < 0.05) in both austral winter (JJA) and summer (DJF) zonal wind between 55⁰-65⁰S. We compare the ice core-based SHWW reconstruction with marine proxy-based Antarctic upwelling reconstructions and find that SPICEcore PSD coarsening occurs coeval with a decrease in δ13C (1938-1972), interpreted as an increase in upwelling of circumpolar deep water due to contraction (southward shift) of the SHWW (Hillenbrand et al., 2017). During the early Holocene, we observe two significant changes in the SHWW, interpreted as latitudinal contractions or southward shifts, at ~10.7-10.0 and 8.5-8.0 ka. These are followed by a major contraction of the SHWW at 6 ka followed by a gradual expansion, as indicated by PSD fining from 6 ka to pre-industrial times.