Abstract. The Greenland Ice Sheet Project 2 glaciochemical series (sodium, potassium, ammonium, calcium, magnesium, sulfate, nitrate, and chloride) provides a unique view of the chemistry of the atmosphere and the history of atmospheric circulation over both the high latitudes and mid-low latitudes of the northern hemisphere. Interpretation of this record reveals a diverse array of environmental signatures that include the documentation of anthropogenically derived pollutants, volcanic and biomass burning events, storminess over marine surfaces, continental aridity and biogenic source strength plus information related to the controls on both high-and low-frequency climate events of the last 110,000 years. Climate forcings investigated include changes in insolation of the order of the major orbital cycles that control the long-term behavior of atmospheric circulation patterns through changes in ice volume (sea level), events such as the Heinrich events (massi've discharges of icebergs first identified in the marine record) that are found to operate on a 6100-year cycle due largely to the lagged response of ice sheets to changes in insolation and consequent glacier dynamics, and rapid climate change events (massive reorganizations of atmospheric circulation) that are demonstrated to operate on 1450-year cycles. Changes in insolation and associated positive feedbacks related to ice sheets m•y assist in explaining favorable time periods and controls on the amplitude of massive rapid climate change events. Explanation for the exa•t timing and global synchroneity of these events is, however, more complicated. Preliminary evidence points to possible solar variability-climate associations for these events and perhaps others that are embedded in our ice-corederived atmospheric circulation records.

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Stable isotope data from waters of lakes in the McMurdo Dry Valleys (MDV) of southern Victoria Land, Antarctica are presented in order to establish the climatic history of this region over the past two millennia. New data from Lake Fryxell and Lake Hoare in Toylor Valley, along with previously published data from Lake Vanda, Wright Valley and Lake Bonney, Taylor Valley are used to infer the recent climatic history of MDV. Lakes Vanda, Fryxell and Bonney appear to have lost their ice covers and evaporated to small, hypersaline ponds by 1000 to ~1200 yr BP. Lake Hoare either desiccated or did not exist prior to 1200 yr BP. These data indicate a major lowering of lake level prior to ~1000 yr BP, followed by a warmer and/or more humid climate since then.

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Rare earth element (REE) concentrations for the alkaline, saline waters of Mono Lake in eastern California are reported. The total REE concentrations of the lake water ranged from 4,68 1 to 7,979 pmol kg-I. Shale-normalized REE profiles for the lake water indicate that the heavy REEs (HREE) are enriched 20-200 times over the light REEs (LREE) compared to shale.The speciation of the REEs in Mono Lake was modeled with a combined specific ion interaction and ion-pairing model which allowed activity coefficients for the major solutes (yM, rX), the REEs (TV), and the REE ion pairs (rMX) to be determined in the high ionic strength lake waters (Z = 1.84 m). The speciation model suggests that essentially all the REEs in solution are complexed with carbonate ions and that >99% of each REE is complexed as Ln(CO,),-species. The carbonate ion concentration of Mono Lake water is 0.27 m. Stability constants for these complexes increase with atomic number; consequently, these complexes are responsible for the HREE enrichments. Activity product calculations for REE phosphate coprecipitates in the high phosphate waters of Mono Lake (i.e. 800-l ,000 pm01 kg-r) indicate that the lake water is close to saturation with respect to these precipitates and suggest that the coprecipitates may effectively limit the maximum dissolved REE concentrations in the lake.The unique, chemically coherent behavior of the rare earth elements (REEs) makes them ideal geochemical tracers for many geologic processes. For example, REEs have been used extensively as sensitive tracers of the processes involved in the petrogenesis of magmatic rocks and to study geochemical processes in the oceans (Goldberg et al. 1963;Elderfield and Greaves 1982;Cullers and Graf 1984). Re-' Present address: