|Title:||Seasonal to centennial-scale variability of microparticle concentration and size distribution in the WAIS Divide ice core over the past 2.4 ka|
|Author:||Kreutz, K.J., Koffman, B.G., Breton, D.J., Dunbar, N.W. and Kurbatov, A.|
|Periodical:||American Geophysical Union, Fall Meeting 2011, abstract #V11D-2539|
We present results from continuous analysis of mineral dust in the upper 577 m (2.4 ka) of the WAIS Divide deep ice core, WDC06A. The core was melted using the UMaine WAIS Melt Monitor system, which allows accurate mm-scale depth co-registration of electrical conductivity and particle data, with subsequent collection of discrete samples for expanded particle, glaciochemical and geochemical analysis. The concentration and size distribution of microparticles were measured using a flow-through Klotz Abakus laser particle detector, developed by Ruth et al (2002) and calibrated with Coulter-Counter measurements. We found that background dust concentrations during the past two millennia have been low, comparable to other sites in interior Antarctica. Particle concentration ranges seasonally from ~20-1000 particles/ml. Particle deposition generally shows an annual signal, although the phasing varies relative to seasonal chemical indicators such as nssSO42-. Dust deposition on decadal to centennial timescales appears to be linked to hemispheric-scale climate variability during the late Holocene, and particularly to the Southern Annular Mode (SAM) climate oscillation. We compared the coarse particle percentage (5-10 µm diameter relative to 1-10 µm diameter) to a proxy record of the SAM developed using sea salt concentrations in the Law Dome, East Antarctica, ice core (Goodwin et al, 2004). Spectral characteristics of the coarse particle percentage at WAIS Divide seem to match the Law Dome proxy for the SAM. This suggests a coherent signal for the SAM and the potential to develop a particle size distribution proxy for the strength of the circum-Antarctic atmospheric circulation. Within the past two centuries of dust deposition, there were several dusty decades in the early-to-mid 1900s followed by a dramatic increase around 1980. Given that the particle size distribution does not show significant coeval change, we infer that this increased dust deposition has been driven primarily by increased emissions in dust source regions, likely though anthropogenic activities.