Reconstructing dust input to the Subarctic North Pacific - Past and Present
Abstract
The Subarctic North Pacific constitutes one of the high-nutrient-low chlorophyll (HNLC) regions of the modern ocean, where the biological pump is relatively inefficient at transferring carbon from the atmosphere to the deep sea. Iron limitation is traditionally suggested as the main controlling factor of biological production/the HNLC status of the Subarctic North Pacific, with iron thought to be primarily delivered by atmospheric dust transport from the East Asian desert areas. However, our understanding of the links between dust, biological production and climate is hampered by the lack of reliable dust flux records in the Subarctic North Pacific as well as longstanding discrepancies among specific techniques that have been used in previous research to reconstruct biological productivity. The lack of reliable dust flux reconstructions from North Pacific sediments is due a variety of reasons, among them sparsity of sediment cores, uncertain age control of the sediments as well as the impact of sediment input other than dust, such as hemipelagic and volcanic material as well as ice-rafted debris. Here, we map and compare spatial patterns of two proxies of eolian dust fluxes (230Thxs-normalized 232Th and 4He fluxes) as well as REE elements (e.g., La/Yb and Th/Sc ratios to deconvolve eolian and volcanic input to the sediments) from 37 multicore core-top sediments across the Subarctic North Pacific, obtained during the INOPEX cruise in 2009. We will present spatial patterns of these tracers to test their validity as proxies of mineral dust and to deconvolve dust and volcanic input to the sediments. The spatial patterns of the reconstructed dust fluxes will be compared to results of published reconstructions of modern dust trajectories to test the validity of these methods to capture modern dust flux patterns to the Subarctic North Pacific. The results from this study will be used for future research focusing on dust flux and productivity changes during the abrupt climate change sequence of the last deglaciation: the sequence from the cold and dusty Heinrich Stadial 1, through the dust-poor Bølling-Allerød warm period and a return to the near-glacial conditions of the Younger Dryas stadial. Ultimately, our results will allows us test the traditional hypothesis of eolian iron input primarily controlling the biological productivity in the Subarctic North Pacific and to evaluate how the Subarctic North Pacific's ecosystem responds to and mediates climate change.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2011
- Bibcode:
- 2011AGUFMPP52A..06W
- Keywords:
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- 1029 GEOCHEMISTRY / Composition of aerosols and dust particles;
- 4901 PALEOCEANOGRAPHY / Abrupt/rapid climate change;
- 4904 PALEOCEANOGRAPHY / Atmospheric transport and circulation;
- 4924 PALEOCEANOGRAPHY / Geochemical tracers