Low-latitude western north atlantic climate variability during the past millennium : insights from proxies and models
Saenger, Casey P.
MetadataShow full item record
LocationWestern North Atlantic
Estimates of natural climate variability during the past millennium provide a frame of reference in which to assess the significance of recent changes. This thesis investigates new methods of reconstructing low-latitude sea surface temperature (SST) and hydrography, and combines these methods with traditional techniques to improve the present understanding of western North Atlantic climate variability. A new strontium/calcium (Sr/Ca) - SST calibration is derived for Atlantic Montastrea corals. This calibration shows that Montastrea Sr/Ca is a promising SST proxy if the effect of coral growth is considered. Further analyses of coral growth using Computed Axial Tomography (CAT) imaging indicate growth in Siderastrea corals varies inversely with SST on interannual timescales. A 440-year reconstruction of low-latitude western North Atlantic SST based on this relationship suggests the largest cooling of the last few centuries occurred from ~1650-1730 A.D., and was ~1ºC cooler than today. Sporadic multidecadal variability in this record is inconsistent with evidence for a persistent 65-80 year North Atlantic SST oscillation. Volcanic and anthropogenic radiative forcing are identified as important sources of externally-forced SST variability, with the latter accounting for most of the 20th century warming trend. An 1800-year reconstruction of SST and hydrography near the Gulf Stream also suggests SSTs remained within about 1ºC of modern values. This cooling is small relative to other regional proxy records and may reflect the influence of internal oceanic and atmospheric circulation. Simulations with an atmospheric general circulation model (AGCM) indicate that the magnitude of cooling estimated by proxy records is consistent with tropical hydrologic proxy records.
Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution September 2009
Suggested CitationThesis: Saenger, Casey P., "Low-latitude western north atlantic climate variability during the past millennium : insights from proxies and models", 2009-09, DOI:10.1575/1912/3102, https://hdl.handle.net/1912/3102
Showing items related by title, author, creator and subject.
Fornace, Kyrstin L. (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 2016-02)Characterizing global and regional climate variability and climate-carbon cycle interactions in the past provides critical context for evaluating present and future climate trends. In this thesis, I use stable isotope ...
Alpert, Alice (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 2016-09)Paleoclimate archives place the short instrumental record of climate variability in a longer temporal context and allow better understanding of the rate, nature and extent by which anthropogenic warming will i ...
Geochemistry of slow-growing corals : reconstructing sea surface temperature, salinity and the North Atlantic Oscillation Goodkin, Nathalie F. (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 2007-06)A 225-year old coral from the south shore of Bermuda (64°W, 32°N) provides a record of decadal-to-centennial scale climate variability. The coral was collected live, and sub-annual density bands seen in x-radiographs ...