Glacial reduction of the North American Monsoon via surface cooling and atmospheric ventilation

Bhattacharya, Tripti; Tierney, Jessica E.; DiNezio, Pedro

doi:10.1002/2017gl073632

Cited by 43 publications

(42 citation statements)

References 38 publications

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“…Similarly, Vasquez-Selem and Heine (2011) noted glacial expansion at the Last Glacial Maximum (LGM), with an associated 6-7 • temperature decrease. Vasquez-Selem and Heine (2011) suggest westerlies as the moisture source, which is consistent with findings of a reduced NAM during the LGM by Bhattacharya et al (2017). We hypothesize that during glacial maxima the Laurentide Ice Sheet influenced westerlies and associated storm tracks to enhance moisture inputs to central Mexico, likely in combination with decreased evaporation associated with lower temperatures, analogous to LGM conditions.…”

Section: Introductionsupporting

confidence: 89%

Scientific drilling of Lake Chalco, Basin of Mexico (MexiDrill)

et al. 2019

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The primary scientific objective of MexiDrill, the Basin of Mexico Drilling Program, is development of a continuous, high-resolution ∼ 400 kyr lacustrine record of tropical North American environmental change. The field location, in the densely populated, water-stressed Mexico City region gives this record particular societal relevance. A detailed paleoclimate reconstruction from central Mexico will enhance our understanding of long-term natural climate variability in the North American tropics and its relationship with changes at higher latitudes. The site lies at the northern margin of the Intertropical Convergence Zone (ITCZ), where modern precipitation amounts are influenced by sea surface temperatures in the Pacific and Atlantic basins. During the Last Glacial Maximum (LGM), more winter precipitation at the site is hypothesized to have been a consequence of a southward displacement of the mid-latitude westerlies. It thus represents a key spatial node for understanding large-scale hydrological variability of tropical and subtropical North America and is at an altitude (2240 m a.s.l.), typical of much of western North America. In addition, its sediments contain a rich record of pre-Holocene volcanic history; knowledge of the magnitude and frequency relationships of the area's explosive volcanic eruptions will improve capacity for risk assessment of future activity. Explosive eruption deposits will also be used to provide the backbone of a robust chronology necessary for full exploitation of the paleoclimate record. Here we report initial results from, and outreach activities of, the 2016 coring campaign.Published by Copernicus Publications on behalf of the IODP and the ICDP. 2 E. T. Brown et al.: Scientific drilling of Lake Chalco, Basin of MexicoMuch is being written about climate change and the impact of rising seas on waterfront populations. But coasts are not the only places affected. Mexico City -high in the mountains, in the center of the country -is a glaring example.

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Section: Introductionsupporting

confidence: 89%

Scientific drilling of Lake Chalco, Basin of Mexico (MexiDrill)

et al. 2019

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“…Moreover, if the North American summer monsoon strengthened (cf. Lachniet et al, 2013;Bhattacharya et al, 2017), then greater increases in precipitation on the eastern slopes that would fall as snow at higher elevations would have further increased accumulation differences across the range.…”

Section: Last Glacial Climate In the Mosquito Rangementioning

confidence: 99%

Late Pleistocene glaciation in the Mosquito Range, Colorado, USA: chronology and climate

Brugger

Laabs

Reimers

et al. 2019

J Quaternary Science

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New cosmogenic 10Be surface exposure ages from 17 moraine boulders in the Mosquito Range of Colorado suggest that glaciers were at their late Pleistocene (Pinedale) maximum extent at ∼21–20 ka, and that ice recession commenced before ∼17 ka. These age limits suggest that the Pinedale Glaciation was synchronous within the Colorado Rocky Mountain region. Locally, the previous (Bull Lake) glaciation appears to have occurred no later than 117 ka, possibly ∼130 ka allowing for reasonable rock weathering rates. Temperature‐index modeling is used to determine the magnitude of temperature depression required to maintain steady‐state mass balances of seven reconstructed glaciers at their maximum extent. Assuming no significant differences in precipitation compared to modern values, mean annual temperatures were ∼8.1 and 7.5 °C lower, respectively, on the eastern and western slopes of the range with quantifiable uncertainties of + 0.8/−0.9 °C. If an average temperature depression of 7.8 °C is assumed for the entire range, precipitation differences − that today are 15–30% greater on the eastern slope due to the influence of winter/early spring snowfall − might have been enhanced. The temperature depressions inferred here are consistent with similarly derived values elsewhere in the Colorado Rockies and those inferred from regional‐scale climate modeling.

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“…Ecosystem-atmosphere CO 2 exchange in western forests is controlled in large part by the annual delivery of water from the melting winter snowpack (Hu, Moore, Burns, & Monson, 2010;Monson et al, 2005;Winchell, Barnard, Monson, Burns, & Molotch, 2016), while summer rains can compensate for snowpack limitations (Berkelhammer, Stefanescu, Joiner, & Anderson, 2017;West, Hultine, Burtch, & Ehleringer, 2007). Summer rain in the southwestern United States is delivered by the North American Monsoon (NAM), a climate system that has been active during the Holocene (Betancourt, 1990;Bhattacharya, Tierney, & DiNezio, 2017). The utilization of soil water from different seasonal precipitation sources, and the photosynthetic efficiencies that are realized by interannual variation in the amounts of winter and summer precipitation, can be inferred through studies of the carbon and oxygen stable-isotope ratios in the α-cellulose of tree rings (Barbour, Walcroft, & Farquhar, 2002;Craig, 1954;Francey & Farquhar, 1982;Leavitt & Long, 1986;Libby & Pandolfi, 1974).…”

Section: Introductionmentioning

confidence: 99%

Disentangling seasonal and interannual legacies from inferred patterns of forest water and carbon cycling using tree‐ring stable isotopes

Szejner

Wright

Belmecheri

et al. 2018

Global Change Biology

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Tree-ring carbon and oxygen isotope ratios have been used to understand past dynamics in forest carbon and water cycling. Recently, this has been possible for different parts of single growing seasons by isolating anatomical sections within individual annual rings. Uncertainties in this approach are associated with correlated climate legacies that can occur at a higher frequency, such as across successive seasons, or a lower frequency, such as across years. The objective of this study was to gain insight into how legacies affect cross-correlation in the δ C and δ O isotope ratios in the earlywood (EW) and latewood (LW) fractions of Pinus ponderosa trees at thirteen sites across a latitudinal gradient influenced by the North American Monsoon (NAM) climate system. We observed that δ C from EW and LW has significant positive cross-correlations at most sites, whereas EW and LW δ O values were cross-correlated at about half the sites. Using combined statistical and mechanistic models, we show that cross-correlations in both δ C and δ O can be largely explained by a low-frequency (multiple-year) mode that may be associated with long-term climate change. We isolated, and statistically removed, the low-frequency correlation, which resulted in greater geographical differentiation of the EW and LW isotope signals. The remaining higher-frequency (seasonal) cross-correlations between EW and LW isotope ratios were explored using a mechanistic isotope fractionation-climate model. This showed that lower atmospheric vapor pressure deficits associated with monsoon rain increase the EW-LW differentiation for both δ C and δ O at southern sites, compared to northern sites. Our results support the hypothesis that dominantly unimodal precipitation regimes, such as near the northern boundary of the NAM, are more likely to foster cross-correlations in the isotope signals of EW and LW, potentially due to greater sharing of common carbohydrate and soil water resource pools, compared to southerly sites with bimodal precipitation regimes.

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Glacial reduction of the North American Monsoon via surface cooling and atmospheric ventilation

Cited by 43 publications

References 38 publications

Scientific drilling of Lake Chalco, Basin of Mexico (MexiDrill)

Scientific drilling of Lake Chalco, Basin of Mexico (MexiDrill)

Late Pleistocene glaciation in the Mosquito Range, Colorado, USA: chronology and climate

Disentangling seasonal and interannual legacies from inferred patterns of forest water and carbon cycling using tree‐ring stable isotopes

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