A Comparison of Orbital-Resolution, late Pleistocene, Alkenone and Faunal-Based Sea-Surface Temperature Reconstructions from the Southwest Pacific
Abstract
Because not every paleotemperature proxy is viable at all geographic locations, sea-surface temperature (SST) estimates from multiple proxies are often compiled into global or regional reconstructions of past climate conditions with the implicit assumption that estimates derived from different proxies can be used interchangeably. However, limited evidence currently exists to support the validity of this assumption. Using paleotemperature data from sediments collected from ODP Site 1125 (42°33'S, 178°10'W, 1365 meters water depth) in the southwest Pacific, we provide a ~1 Myr, orbital-scale SST proxy comparison of alkenone-derived SST data to previously published faunal assemblage SST data from the Pleistocene. These UK'37 and faunal assemblage SST records show strong structural similarity and yield remarkably similar estimates for basic climate metrics across each of the time series, including mean (14.9°C versus 14.4°C, respectively), standard deviation (both 1.6°C), and range (7.8°C versus 7.5°C, respectively). Spectral analysis reveals that the alkenone and faunal records are similar, both containing a dominant 100 kyr beat, with additional spectral power in the ~41 kyr and 23 kyr bands. Regression analysis yields a fairly strong (r = 0.64) and highly statistically significant correlation between the two SST records. Results from this work indicate that these two proxies would yield very similar estimates for the paleoclimate metrics most commonly used in empirical paleoclimate reconstructions that seek to document the evolution of climate through time. However, significant disparities between SST estimates exist for some time intervals, particularly during extreme glacial and interglacial intervals. Thus, treating these proxies interchangeably when employing the time-slab or time-slice approaches that are typically employed in modeling studies could be problematic. We attribute the discrepancies between the two SST proxy estimates during these times to two factors: incursions of cold water across the Subtropical Front during extreme glacial periods and a difference in the season of maximum alkenone production versus that of foraminiferal production.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFMPP14B..01L
- Keywords:
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- 0419 Biomineralization;
- BIOGEOSCIENCES;
- 0454 Isotopic composition and chemistry;
- BIOGEOSCIENCES;
- 0473 Paleoclimatology and paleoceanography;
- BIOGEOSCIENCES;
- 4994 Instruments and techniques;
- PALEOCEANOGRAPHY