Mysteries, Conundrums, and Paradoxes: Insights on the Past 50,000 Years of Climate Evolution from Greenland Ice Core Temperature Reconstructions

• Main Author: Martin, Kaden
• Other Authors: Buizert, Christo, Brook, Ed, Edwards, Jon, Michael, Kalk, Riddell-Young, Ben, Beaudette, Ross, Severinghaus, Jeff, Sowers, Todd, Williams, Olivia, Fudge, TJ, Mederbel, Farhana, Oyabu, Ikumi, Kawamura, Kenji, Kirk, Marie, Koldtoft, Iben, Steffensen, JP, Blunier, Thomas, Neizgoda, Kyle, Noone, David, Schellman, Heidi, Walczak, Mo, College of Earth, Ocean, and Atmospheric Sciences
• Format: Doctoral or Postdoctoral Thesis
• Language: English; unknown
• Published: Oregon State University
• Subjects: Antarc*; Antarctic; Antarctica; Greenland; Greenland ice core; Greenland ice cores; Greenland Ice Sheet Project; Hudson Strait; ice core; Ice Sheet; Iceberg*; North Atlantic
• Online Access: https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/c821gt78j

The last glacial period is characterized by abrupt climate change on millennial timescales. One such mode of variability, the Heinrich mode, remains poorly characterized in Greenland. These enigmatic periods are associated with extremely cold conditions in the North Atlantic (the Heinrich Stadial) and rapid discharges of icebergs from the Hudson Strait into the North Atlantic (the Heinrich Event). There is evidence of global disruptions to biogeochemical and hydrological cycles associated with these periods, alongside rapid warming in Antarctica. However, these periods have no expression in the water isotope composition of Greenland ice cores, a commonly used proxy for paleo-temperature reconstruction. This suggests a Proximity Paradox: distal climate systems are more sensitive to Heinrich-type variability than Greenland is, despite the latter’s proximity and sensitivity to changes in North Atlantic oceanographic conditions. This dissertation seeks to characterize the Greenland climate response to Heinrich-type variability through an alternative firn-based reconstruction method, and to assess possible solutions to the Proximity Paradox within an isotopeenabled climate model. We additionally characterize the Greenland climate evolution from the Last Glacial Maximum through the Holocene via a multi-core and multi-proxy reconstruction of Greenland climate. First, we examine the climate signature of Heinrich Events and Heinrich Stadials in Greenland. We reconstruct temperature and accumulation variability from the Greenland Ice Sheet Project 2 (GISP2) ice core from 11-50kaBP (thousands of years before present, present = 1950), covering Heinrich Events 1-5. Our method utilizes an inverse model to calculate the climate-dependent densification rate of the firn (the snow-ice transition zone), which is accurately recorded by d15N-N2 (d15N) and Dage. Our Greenland reconstructions are synchronized to Antarctic ice cores by centennialscale CH4 variability, allowing for the precise phasing of climate variability between them ...