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Department Seminar Speaker - 03/27/2017 - Ashley Maloney, University of Washington

"Late Holocene hydroclimate in the South Pacific Convergence Zone"

Stable hydrogen isotope ratios from lipid biomarkers can reveal pre-instrumental natural variability in the Southern Hemisphere’s largest precipitation feature, the South Pacific Convergence Zone (SPCZ). Dinosterol, a dinoflagellate lipid biomarker, was purified from sediment cores collected from 9 freshwater lakes on 5 islands in the Solomon Islands, Vanuatu, and Wallis. Molecular paleohydrology is well suited for tropical rainfall reconstructions because hydrogen isotope ratios of precipitation are related to rainfall rate, algal lipids track environmental water isotope ratios, and lipids are well preserved in sediments. Lipid hydrogen isotope ratios are also influenced by environmental parameters such as salinity, light, temperature, and growth rate, motivating the use of multiple lakes in each region. An exciting addition to this work shows that dinosterol hydrogen isotope ratios in surface sediments are well correlated with satellite rainfall rates, allowing quantitative reconstructions. The records indicate rainfall rates in the Solomon Islands were ~2 mm/day greater during the Little Ice Age (~1400-1850) to present compare to 1500 years ago to the Medieval Warm Period (~800-1200). Precipitation rates along the southern and southwestern edges of the SPCZ in Vanuatu and Wallis were up to 1 mm/day less during the early Little Ice Age compared to today.

Location: Guyot Hall - Room 10

Date/Time: 03/27/17 at 12:30 pm - 03/27/17 at 1:30 pm

Category: Seminar

Department: Geosciences