Abstract:
This thesis presents a water-isotope (δD) record from 1900 to 2009 for the Roosevelt Island Climate Evolution (RICE) ice core, Antarctica. Examination of the RICE isotope record with observation data (using global reanalysis and SST datasets) revealed details of the climate signal that is preserved within the full 763 m isotope record. RICE δD provides a proxy record, which captures the central tropical Pacific ENSO variability, the significant (p < 0.01) central Pacific δD-SST correlation pattern contain the Niño-4 SST region. Central tropical Pacific ENSO variability projects upon the Amundsen Sea region via a Pacific–South American pattern (PSA)-like teleconnection. RICE δD is primarily influenced by Amundsen Sea circulation, which coincides with the leading PSA pattern’s (PSA1) circulation focal point in the Amundsen Sea. Additionally, RICE regional physical setting (sheltered from direct impact from Amundsen Sea cyclones by WA orography) offers a unique setting, where enriched isotopes only are associated with one PSA1 polarity (El Niño, PSA1+, Amundsen Sea anticyclones). In contrast, during La Niña and Amundsen Sea cyclones, δD is depleted. Combined these settings, provides a compelling explanation to why RICE δD preserves PSA1 and ENSO variability. On interannual and seasonal time scales, the RICE δD variability is well-explained by the PSA teleconnections and their interactions over the Pacific sector. The influence from PSA2 on δD is strong during the beginning of the year (December–February, DJF). In contrast, the PSA1 influence is strong during the latter part of the year, peaking in spring (September–November, SON). The isotope record appears to preserve tropical Pacific El Niño-like interdecadal variability, particularly a decadal-signal from the central-Pacific (Niño-4 SST region) and from the Pacific-wide Interdecadal Pacific Oscillation (IPO). On decadal-scales RICE δD is modulated by ENSO and Southern Annular Mode (SAM); when the correlation with SAM is active (during IPO+) δD appears to be in a depleted state and when the correlation with SAM breaks down (during IPO−) δD appears to be in a relatively enriched state. A RICE δD SST proxy reconstruction can potentially provide a record longer than the currently available observational datasets, allowing for examination of intrinsic decadal-scale tropical Pacific climate variability and its extratropical impact.
