Date of Award

12-2014

Level of Access Assigned by Author

Campus-Only Thesis

Degree Name

Master of Science (MS)

Department

Earth Sciences

Advisor

Paul Andrew Mayewski

Second Committee Member

Andrei V. Kurbatov

Third Committee Member

Sharon B. Sneed

Abstract

The Climate Change Institute’s W. M. Keck Laser Ice Facility laser ablation inductively coupled plasma spectrometer (LA-ICP-MS) is capable of collecting a sample every 121 micrometers, a resolution on the scale of ice crystal triple junctions and grain boundaries in ice cores. Recent publications suggest that these features can allow amplification of impurity concentrations, and possibly allow migration of impurities through veins, which potentially could obscure climate signals preserved in polar ice. LA-ICP-MS data reveal that such features modify these signals by less than 6% in the case of Na, Ca, and Fe in GISP2 ice deposited at the beginning of the Holocene.

Preservation at the micrometer scale directly relates with climate proxies produced from climate records. The RICE deep ice core contains a ~70 kyr record of atmospheric circulation over the Ross Sea region, and the barium time series therein is strongly correlated with the Ross Sea Polynya throughout the period of overlap with the ERA-Interim climate reanalysis dataset (1979-2011). This new proxy captures ~1150 years of Ross Sea Polynya fluctuation history, covering periods of sea ice advance and retreat in the polynya, Ross Ice Shelf calving events, the Medieval Warm Period, Little Ice Age and the Modern Era. Our proxy adds to previous studies by revealing that the Ross Sea Polynya did not react homogeneously to Little Ice Age climatic conditions, as Ross Sea Polynya area underwent stepwise fluctuations. Katabatic and Southern Hemisphere Westerly wind strength, Amundsen Sea Low depth, and proximal cyclones, as well as cooler temperatures were not synchronous over this period, and their influence on the polynya is highlighted in the inhomogeneity. The Modern Era is marked by the smallest RSP area observed, most likely due to SHW contraction and strengthening, overpowering Ross Sea katabatic wind strength. This Ross Sea Polynya proxy serves as an indication of biological productivity, sea ice production, katabatic and southern hemisphere westerly wind strength, Antarctic Bottom Water formation, and marine CO2 Sequestration in the Ross Sea Embayment

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