LDEO Earth Science Colloquium presents:
The Highest Water
with Dr. Guleed Ali, Assistant Professor, Stony Brook University.
Water availability dictates where societies and ecosystems can thrive, and that availability can reorganize within a human lifetime. Speleothem records capture such reorganizations vividly, on timescales of decades, but their magnitude has resisted quantification. To capture magnitude, we need an archive that measures water balance in physical units. Closed-basin lakes provide that archive. They gauge water balance directly and record it through shoreline elevation.
A bird’s eye view of the western US sparkles with shorelines etched across dry valleys of the Great Basin. They were left by lakes that reached high stands during Heinrich Stadial 1. Whether those maxima record the millennial cooling of that stadial or a briefer event within it has remained unresolved. The chronology of the shorelines rests largely on radiocarbon dating, whose uncertainties and biases span centuries to millennia, far longer than the climate shifts themselves.
Uranium-series dating of carbonates overcomes that limit. Here I use it to reconstruct the rise and fall of Mono Lake, California. At roughly 16,000 years ago, the lake rose ~50 m to its highest level in tens of thousands of years, reaching that level within 180 ± 90 years. High stands in other regional lakes fall within the same window. Their timing, brevity, and spatial coherence implicate Heinrich Event 1, a sudden iceberg and meltwater discharge into the North Atlantic. Climate models simulate exactly this wetting of the western US under North Atlantic cooling.
Resolving an event this brief was a geomorphic and stratigraphic problem before it was a geochronologic one. I will describe how landform mapping, stratigraphic bracketing, and stringent sample selection combine into a template for recovering decadal to centurial hydroclimate from the deep geologic record.
The Earth Science Colloquium Series, sponsored by Lamont-Doherty Earth Observatory and Columbia University Department of Earth and Environmental Sciences (DEES), provides a lively forum for discussing a wide variety of topics within the Earth sciences and related fields. Colloquia are attended by the full range of scientific and technical staff at LDEO. Colloquium attendance is required of all pre-orals DEES graduate students.
Host: Dr. Sidney Hemming, Arthur D. Storke Memorial Professor, Department of Earth and Environmental Sciences and Geochemistry Division, LDEO.
