Influences of the seasonal Indian monsoons, 1900-1993 CE: Sub-annual sea surface temperature and precipitation reconstructed from laminated Pakistan Margin sediments
Abstract
Laminated Pakistan Margin marine sediments are excellent archives of past climate and oceanographic conditions in the Northeast Arabian Sea. We reconstruct 20th century sub-annual sea surface temperature (SST) and precipitation using varved sediment core SO90-58KG to examine interannual variability in the seasonal Indian monsoons, as the annual SST cycle is driven by upward mixing of cooler waters during the Northeast monsoon, and precipitation may be linked with the Southwest monsoon.
We apply a novel mass spectrometry imaging technique to measure and map the downcore distribution of glycerol dialkyl glycerol tetraethers and alkenones in in-tact sediment surfaces with 100 µm resolution, using MALDI FT-ICR MS. These same samples are analyzed with micro-XRF in 50 µm resolution to generate paired elemental maps. Reconstructed SSTs were calculated from the crenarchaeol-caldarchaeol tetraether index (CCaT) and UK'37 proxies, respectively, with a temporal resolution of 6-8 points per year, and verified with extraction-based methods. Reconstructed SSTs for both proxies contain congruent trends, and align with the annual range of instrumental measurements (23-30 °C). The annual cycles in SST are prominent in the reconstructed series and highly significant in their power spectra. Principal component analysis was applied to the elemental measurements, and a primary component is associated with siliciclastic elements (Si, K, Ti, Fe). The siliciclastic component is compared with historical precipitation records to develop a proxy for precipitation-driven river runoff.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2020
- Bibcode:
- 2020AGUFMPP033..04N
- Keywords:
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- 3305 Climate change and variability;
- ATMOSPHERIC PROCESSES;
- 3337 Global climate models;
- ATMOSPHERIC PROCESSES;
- 3344 Paleoclimatology;
- ATMOSPHERIC PROCESSES