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Falster G, Konecky B, Coats S, Stevenson S. Forced changes in the Pacific Walker circulation over the past millennium. Nature 2023; 622:93-100. [PMID: 37612511 PMCID: PMC10550830 DOI: 10.1038/s41586-023-06447-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2022] [Accepted: 07/14/2023] [Indexed: 08/25/2023]
Abstract
The Pacific Walker circulation (PWC) has an outsized influence on weather and climate worldwide. Yet the PWC response to external forcings is unclear1,2, with empirical data and model simulations often disagreeing on the magnitude and sign of these responses3. Most climate models predict that the PWC will ultimately weaken in response to global warming4. However, the PWC strengthened from 1992 to 2011, suggesting a significant role for anthropogenic and/or volcanic aerosol forcing5, or internal variability. Here we use a new annually resolved, multi-method, palaeoproxy-derived PWC reconstruction ensemble (1200-2000) to show that the 1992-2011 PWC strengthening is anomalous but not unprecedented in the context of the past 800 years. The 1992-2011 PWC strengthening was unlikely to have been a consequence of volcanic forcing and may therefore have resulted from anthropogenic aerosol forcing or natural variability. We find no significant industrial-era (1850-2000) PWC trend, contrasting the PWC weakening simulated by most climate models3. However, an industrial-era shift to lower-frequency variability suggests a subtle anthropogenic influence. The reconstruction also suggests that volcanic eruptions trigger El Niño-like PWC weakening, similar to the response simulated by climate models.
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Affiliation(s)
- Georgina Falster
- Australian Research Council Centre of Excellence for Climate Extremes, Canberra, Australian Capital Territory, Australia.
- Department of Earth and Planetary Sciences, Washington University in St. Louis, St. Louis, MO, USA.
- Research School of Earth Sciences, Australian National University, Canberra, Australia.
| | - Bronwen Konecky
- Department of Earth and Planetary Sciences, Washington University in St. Louis, St. Louis, MO, USA
| | - Sloan Coats
- Department of Earth Sciences, University of Hawai'i at Mānoa, Honolulu, HI, USA
| | - Samantha Stevenson
- Bren School of Environmental Science and Management, University of California, Santa Barbara, Santa Barbara, CA, USA
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Dee SG, Nusbaumer J, Bailey A, Russell JM, Lee JE, Konecky B, Buenning NH, Noone DC. Tracking the Strength of the Walker Circulation with Stable Isotopes in Water Vapor. J Geophys Res Atmos 2018; 123:7254-7270. [PMID: 30467529 PMCID: PMC6242291 DOI: 10.1029/2017jd027915] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/18/2017] [Accepted: 05/25/2018] [Indexed: 05/05/2023]
Abstract
General circulation models (GCMs) predict that the global hydrological cycle will change in response to anthropogenic warming. However, these predictions remain uncertain, in particular for precipitation [IPCC, 2013]. Held and Soden [2006] suggest that as lower-tropospheric water vapor concentration increases in a warming climate, the atmospheric circulation and convective mass fluxes will weaken. Unfortunately, this process is difficult to constrain, as convective mass fluxes are poorly observed and incompletely simulated in GCMs. Here, we demonstrate that stable hydrogen isotope ratios in tropical atmospheric water vapor can trace changes in temperature, atmospheric circulation and convective mass flux in a warming world. We evaluate changes in temperature, the distribution of water vapor, vertical velocity (ω) and advection, and water isotopes in vapor (δD V ) in water isotopeenabled GCM experiments for modern vs. high CO 2 atmospheres to identify spatial patterns of circulation change over the tropical Pacific. We find that slowing circulation in the tropical Pacific moistens the lower troposphere and weakens convective mass flux, both of which impact the δD of water vapor in the mid-troposphere. Our findings constitute a critical demonstration of how water isotope ratios in the tropical Pacific respond to changes in radiative forcing and atmospheric warming. Moreover, as changes in δD V can be observed by satellites, our results develop new metrics for the detection of global warming impacts to the hydrological cycle and, specifically, the strength of the Walker Circulation.
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Affiliation(s)
- Sylvia G Dee
- Brown University, Department of Earth, Environmental, and Planetary Sciences, Providence, RI 02912
- Brown University, Institute at Brown for Environment and Society, Providence, RI 02912
| | | | | | - James M Russell
- Brown University, Department of Earth, Environmental, and Planetary Sciences, Providence, RI 02912
- Brown University, Institute at Brown for Environment and Society, Providence, RI 02912
| | - Jung-Eun Lee
- Brown University, Department of Earth, Environmental, and Planetary Sciences, Providence, RI 02912
- Brown University, Institute at Brown for Environment and Society, Providence, RI 02912
| | | | - Nikolaus H Buenning
- Department of Earth Sciences, University of Southern California, Los Angeles, CA, 90089
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Seimon TA, Seimon A, Yager K, Reider K, Delgado A, Sowell P, Tupayachi A, Konecky B, McAloose D, Halloy S. Long-term monitoring of tropical alpine habitat change, Andean anurans, and chytrid fungus in the Cordillera Vilcanota, Peru: Results from a decade of study. Ecol Evol 2017; 7:1527-1540. [PMID: 28261462 PMCID: PMC5330894 DOI: 10.1002/ece3.2779] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2016] [Revised: 12/23/2016] [Accepted: 01/03/2017] [Indexed: 11/26/2022] Open
Abstract
The Cordillera Vilcanota in southern Peru is the second largest glacierized range in the tropics and home to one of the largest high‐alpine lakes, Sibinacocha (4,860 m). Here, Telmatobius marmoratus (marbled water frog), Rhinella spinulosa (Andean toad), and Pleurodema marmoratum (marbled four‐eyed frog) have expanded their range vertically within the past century to inhabit newly formed ponds created by ongoing deglaciation. These anuran populations, geographically among the highest (5,200–5,400 m) recorded globally, are being impacted by the chytrid fungus Batrachochytrium dendrobatidis (Bd), and the disease it causes, chytridiomycosis. In this study, we report results from over a decade of monitoring these three anuran species, their habitat, and Bd infection status. Our observations reveal dynamic changes in habitat including ongoing rapid deglaciation (18.4 m/year widening of a corridor between retreating glaciers from 2005 to 2015), new pond formation, changes in vegetation in amphibian habitat, and widespread occurrence of Bd in amphibians in seven sites. Three of these sites have tested positive for Bd over a 9‐ to 12‐year period. In addition, we observed a widespread reduction in T. marmoratus encounters in the Vilcanota in 2008, 2009, and 2012, while encounters increased in 2013 and 2015. Despite the rapid and dynamic changes in habitat under a warming climate, continued presence of Bd in the environment for over a decade, and a reduction in one of three anuran species, we document that these anurans continue to breed and survive in this high Andean environment. High variability in anuran encounters across sites and plasticity in these populations across habitats, sites, and years are all factors that could favor repopulation postdecline. Preserving the connectivity of wetlands in the Cordillera Vilcanota is therefore essential in ensuring that anurans continue to breed and adapt as climate change continues to reshape the environment.
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Affiliation(s)
- Tracie A. Seimon
- Wildlife Conservation SocietyZoological Health ProgramBronxNYUSA
| | - Anton Seimon
- Department of Geography and PlanningAppalachian State UniversityBooneNCUSA
| | - Karina Yager
- School of Marine and Atmospheric SciencesStony Brook UniversityStony BrookNYUSA
| | - Kelsey Reider
- Department of Biological SciencesFlorida International UniversityMiamiFLUSA
| | - Amanda Delgado
- Museo de Historia NaturalUniversidad Nacional de San Antonio Abad del CuscoCuscoPeru
| | | | | | - Bronwen Konecky
- Cooperative Institute for Research in Environmental SciencesUniversity of Colorado BoulderBoulderCOUSA
| | - Denise McAloose
- Wildlife Conservation SocietyZoological Health ProgramBronxNYUSA
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Otto-Bliesner BL, Russell JM, Clark PU, Liu Z, Overpeck JT, Konecky B, deMenocal P, Nicholson SE, He F, Lu Z. Coherent changes of southeastern equatorial and northern African rainfall during the last deglaciation. Science 2014; 346:1223-7. [PMID: 25477460 DOI: 10.1126/science.1259531] [Citation(s) in RCA: 146] [Impact Index Per Article: 14.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
During the last deglaciation, wetter conditions developed abruptly ~14,700 years ago in southeastern equatorial and northern Africa and continued into the Holocene. Explaining the abrupt onset and hemispheric coherence of this early African Humid Period is challenging due to opposing seasonal insolation patterns. In this work, we use a transient simulation with a climate model that provides a mechanistic understanding of deglacial tropical African precipitation changes. Our results show that meltwater-induced reduction in the Atlantic meridional overturning circulation (AMOC) during the early deglaciation suppressed precipitation in both regions. Once the AMOC reestablished, wetter conditions developed north of the equator in response to high summer insolation and increasing greenhouse gas (GHG) concentrations, whereas wetter conditions south of the equator were a response primarily to the GHG increase.
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Affiliation(s)
- Bette L Otto-Bliesner
- Climate and Global Dynamics Division, National Center for Atmospheric Research, Boulder, CO 80307-3000, USA.
| | - James M Russell
- Department of Earth, Environmental, and Planetary Sciences, Brown University, Providence, RI 02912, USA
| | - Peter U Clark
- College of Earth, Ocean, and Atmospheric Sciences, Oregon State University, Corvallis, OR 97331, USA
| | - Zhengyu Liu
- Center for Climatic Research and Department of Atmospheric and Oceanic Sciences, University of Wisconsin-Madison, Madison, WI 53706, USA. Laboratory for Climate, Ocean and Atmosphere Studies, School of Physics, Peking University, Beijing 100871, P. R. China
| | - Jonathan T Overpeck
- Department of Geosciences and Institute of the Environment, University of Arizona, Tucson, AZ 85721, USA
| | - Bronwen Konecky
- College of Earth, Ocean, and Atmospheric Sciences, Oregon State University, Corvallis, OR 97331, USA. Cooperative Institute for Research in Environmental Sciences, University of Colorado Boulder, Boulder, CO 80309, USA
| | - Peter deMenocal
- Department of Earth and Environmental Sciences, Columbia University, New York, NY 10027, USA
| | - Sharon E Nicholson
- Department of Earth, Ocean, and Atmospheric Science, Florida State University, Tallahassee, FL 32306, USA
| | - Feng He
- Center for Climatic Research and Department of Atmospheric and Oceanic Sciences, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Zhengyao Lu
- Laboratory for Climate, Ocean and Atmosphere Studies, School of Physics, Peking University, Beijing 100871, P. R. China
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