Glacial-Interglacial Variability in North American Monsoon Strength
Abstract
The North American monsoon (NAM) is a key feature of modern climate in southwest North America, contributing ~50% of annual precipitation in the southwest United States and up to ~90% of annual precipitation in northwest Mexico. Understanding the impacts of anthropogenic climate change on the NAM is therefore integral to understanding the region's future hydroclimate. The effect of warming on the NAM is largely uncertain, however, as model projections broadly disagree and reconstructing the system in a paleoclimate context has been limited by difficulties in isolating a summer-precipitation signal in many proxy systems. The hydrogen isotopic composition of leaf wax fatty acids (δDwax) has recently been demonstrated to track the relative contribution of summer precipitation to annual totals in southwest North America and thus can serve as a quantitative measure of past NAM rainfall. To better understand variability in the NAM across glacial-interglacial cycles, we generated a 150 kyr reconstruction of NAM strength from δDwax for two Gulf of California sediment cores. Our preliminary results indicate that the NAM was enhanced during interglacials and suppressed during glacial periods. These findings are consistent with previous studies that found a progressive strengthening of the NAM through deglaciation into the mid-Holocene. Furthermore, between the two interglacial periods, it appears that the NAM was stronger during the slightly warmer Last Interglacial than the Holocene. More work is needed to understand the mechanisms behind this pattern, but it appears that warmer climates are associated with an intensified NAM.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFMPP21C1615M
- Keywords:
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- 1616 Climate variability;
- GLOBAL CHANGE;
- 1622 Earth system modeling;
- GLOBAL CHANGE;
- 1626 Global climate models;
- GLOBAL CHANGE;
- 4934 Insolation forcing;
- PALEOCEANOGRAPHY