Atmospheric regime of dust and salt through 75,000 years of Taylor Dome ice core: Refinement by measurement of major, minor, and trace metal suites

Measurement of absolute and relative amounts of dust and salt deposited in the polar ice record is central to several fields of study, including nutri ent delivery, atmospheric deposition of trace elements, past wind strengths , dust provenance, and other aspects of climate and geochemical history. We present a method intended to give a more accurate picture than has been po ssible before of the total amounts and relative proportions of the dust and salt deposited by the atmosphere into polar ice. It also permits us to dis tinguish different compositional types of dust in the ice. The method is ba sed on precise measurement of a suite of several metals whose proportions c ontrast strongly between dust and salt and vary substantially between dust types. We apply the method to a small suite of ice samples from the Taylor Dome core in coastal West Antarctica. In full glacial times, when total imp urities were high and dust dominated over salt, wind strength in the West A ntarctic region was apparently high, and extensive sea-ice cover prevented incorporation of salt into the atmospheric load. At the termination of the glacial period, increased salt in the dust-salt mixture indicates that sea ice diminished, but wind strength continued high, and unchanged dust compos ition indicates unchanged source areas. At about 10,000-11,000 y.B.P., sea- ice cover appears to have briefly returned to glacial conditions, but wind conditions remained in the milder postglacial condition. Soon after, sea ic e retreated, and an abrupt change in dust composition indicates changed sou rce materials or terranes. If extended by analysis of more samples from mor e sites, such information on salt and dust could provide firm constraints o n past wind strengths, extent of sea-ice cover, deposition fluxes of salt a nd dust, and changing continental source areas of dust, for both polar regi ons of the Earth.