Neopluvial

Neopluvial is a term referring to a phase of wetter and colder climate that occurred during the late Holocene in the Western United States. During the Neopluvial, water levels in a number of now-dry lakes and closed lakes such as the Great Salt Lake rose and vegetation changed in response to increased precipitation. The event was not exactly synchronous everywhere, with neopluvial lake-level rises occurring between 6,000 and 2,000 years ago. It is correlative to the Neoglacial period.

Evidence

The neopluvial took place in the western United States during the late Holocene,[1] causing the levels of lakes in the Great Basin to increase[2] and previously dry lakes and springs to refill.[3] It has been observed in Great Salt Lake,[4] Fallen Leaf Lake,[5] Lake Cochise,[6] the Mojave Desert,[7] Mono Lake, Owens Lake, Pyramid Lake,[5] San Luis Lake,[6] Silver Lake,[7] Summer Lake,[8] Tulare Lake,[9] Walker Lake[5] and Winnemucca Lake.[10]

During the Neopluvial, the Great Salt Lake became fresher,[4] and Pyramid Lake reached a water level of 1,186 metres (3,891 ft) above sea level.[5] Walker Lake, Owens Lake and Mono Lake experienced their highest Holocene water levels,[5] with the volumes of the latter two lakes more than doubling.[11] Likewise water levels in Lake Tahoe rose to the point of overflowing into the Truckee River.[12] Silver Lake in the Mojave Desert formed a perennial lake and vegetation was more widespread in the Little Granite Mountains.[7] Summer Lake rose above its present-day level to an elevation of c. 1,278 metres (4,193 ft),[13] although it was not as high as during the mid-Holocene.[8] Water levels rose in Tulare Lake as well.[9]

In the White Mountains, meadows formed during the Neopluvial.[14] Ice patches in the Beartooth Mountains[15] and glaciers grew in the Sierra Nevada,[16] sagebrush steppe, green Mormon tea and other vegetation expanded in the Great Salt Lake region,[17] marshes expanded in the central and northern Great Basin,[18] mammal communities in the Lake Bonneville basin changed with the return of the long-tailed pocket mouse, the Great Basin pocket mouse and the Western harvest mouse to sites where they were not present before and increased abundances of even-toed ungulates,[19] and tree lines dropped, with the lower limit of wooden vegetation penetrating into deserts.[20] Counterintuitively, higher tree line elevations in the Lake Bonneville area occurred during the Neopluvial, which may indicate warmer summers.[21]

In the Owens Valley region, during the Neopluvial the human population became more sedentary and trans-Sierra Nevada trade became established ("Newberry"/"Middle Archaic Period").[22] Population around Lake Alvord increased during this time and lasted even after the Neopluvial had ended there.[3]

Chronology

The beginning of the Neopluvial occurred about 6,000 years before present, but did not occur everywhere at the same time:[12]

  • The Neopluvial occurred between 4,000 and 2,000 years before present in the Carson Sink.[16] The Neopluvial in the Lake Lahontan basin ended about 2,000 years ago.[3]
  • In Fallen Leaf Lake, the Neopluvial occurred 3,700 years before present in Fallen Leaf Lake. The end occurred 3,650 years before present;[5] after that point precipitation became more irregular until the onset of the Little Ice Age about 3,000 years later.[23]
  • Its occurrence is dated between 5,100 and 2,650 years before present in the central-northern Great Basin,[18]
  • In the Great Salt Lake, the Neopluvial commenced 5,000 years before present and water levels reached their maximum between 3,000 and 2,000 years before present.[4]
  • It took place between 3,000 and 4,000 years before present in Lake Cochise.[6]
  • It occurred between 4,000 and 2,500 years before present in the Mojave Desert.[7]
  • In Pyramid Lake, the Neopluvial commenced starting from 5,000 years before present and reached a maximum between 4,100 and 3,800 years before present in Pyramid Lake.[5]
  • High elevation lakes in the Rocky Mountains with small watersheds, particularly sensitive to a changing water balance, showed synchronous increase in lake levels from 6,000 to 5,000 years before present, centered at 5,700 years ago.[24]
  • In the Summer Lake area, the Neopluvial is dated to have occurred between 4,000 and 1,900 years ago.[13]
  • Rising water levels in Lake Tahoe drowned trees between 4,800 and 5,700 years before present.[12]
  • In Tulare Lake, the Neopluvial lasted between 4,500 and 2,800 years before present; after that a severe drought occurred.[9]

The Neopluvial is in part correlative to the Neoglacial,[18] and might have been caused by a change in winter conditions over the North Pacific.[25] This cooling is primarily explained by steadily declining summer insolation, though synchronous patterns in hydrological responses at sub-millennial scales may be linked to atmospheric circulation shifts driven by factors such as internal variability in ocean-atmosphere teleconnections.[24] Strengthening ENSO variability, a cooling of the North Pacific and a southward shift of the Pacific jet stream also coincided with the Neopluvial.[26] The neopluvial resembles the Pluvial period that occurred in western North America during the late Last Glacial Maximum,[27] but was much weaker than the LGM wet period.[4]

Terminology

The term "neopluvial" was coined in 1982 and originally referred to high lake levels in Summer Lake.[10] The term has also been used for a mid-to-late Holocene phase of increased moisture noted in the form of increased wetness in eastern Texas, potentially linked to a stronger monsoon or to the neopluvial of the western US.[28]

References
  1. Hockett 2015, p. 293.
  2. Hockett 2015, p. 299.
  3. Pettigrew, Richard M. (1984). "Prehistoric Human Land-use Patterns in the Alvord Basin, Southeastern Oregon". Journal of California and Great Basin Anthropology. 6 (1): 82–83. JSTOR 27825172 – via https://escholarship.org/uc/item/83g062fb.
  4. Madsen 2000, p. 157.
  5. Noble, Paula; Zimmerman, Susan; Ball, Ian; Adams, Kenneth; Maloney, Jillian; Smith, Shane (2016-04-01). "Late Holocene subalpine lake sediments record a multi-proxy shift to increased aridity at 3.65 kyr BP, following a millennial-scale neopluvial interval in the Lake Tahoe watershed and western Great Basin, USA". Egu General Assembly Conference Abstracts. 18: EPSC2016–7533. Bibcode:2016EGUGA..18.7533N.
  6. Yuan, Koran & Valdez 2013, p. 155.
  7. Jones, Terry L.; Klar, Kathryn; Archaeology, Society for California (2007). California Prehistory: Colonization, Culture, and Complexity. Rowman Altamira. p. 33. ISBN 9780759108721.
  8. "AN EARTHQUAKE CLUSTER FOLLOWED THE DRYING OF PLEISTOCENE LAKE CHEWAUCAN, CENTRAL OREGON BASIN AND RANGE". gsa.confex.com. Retrieved 2017-07-06.
  9. Negrini, Robert M.; Wigand, Peter E.; Draucker, Sara; Gobalet, Kenneth; Gardner, Jill K.; Sutton, Mark Q.; Yohe, Robert M. (2006-07-01). "The Rambla highstand shoreline and the Holocene lake-level history of Tulare Lake, California, USA". Quaternary Science Reviews. 25 (13): 1614. Bibcode:2006QSRv...25.1599N. doi:10.1016/j.quascirev.2005.11.014.
  10. Adams, Kenneth D.; Rhodes, Edward J. (2019). "Late Pleistocene to present lake-level fluctuations at Pyramid and Winnemucca lakes, Nevada, USA". Quaternary Research. 92 (1): 24. Bibcode:2019QuRes..92..146A. doi:10.1017/qua.2018.134. ISSN 0033-5894.
  11. "HOW WET CAN IT GET? DEFINING FUTURE CLIMATE EXTREMES BASED ON LATE HOLOCENE LAKE-LEVEL RECORDS". gsa.confex.com. Retrieved 2017-07-06.
  12. Noble et al. 2016, p. 206.
  13. Badger, Thomas C.; Watters, Robert J. (2004-05-01). "Gigantic seismogenic landslides of Summer Lake basin, south-central Oregon". GSA Bulletin. 116 (5–6): 619. Bibcode:2004GSAB..116..687B. doi:10.1130/B25333.1. ISSN 0016-7606.
  14. Ababneh, Linah; Woolfenden, Wallace (2010-03-15). "Monitoring for potential effects of climate change on the vegetation of two alpine meadows in the White Mountains of California, USA". Quaternary International. 23rd Pacific Climate Workshop (PACLIM). 215 (1): 4. Bibcode:2010QuInt.215....3A. doi:10.1016/j.quaint.2009.05.013.
  15. Chellman, Nathan; Pederson, Gregory T.; Lee, Craig M.; McWethy, David B.; Puseman, Kathryn; Stone, Jeffery R.; Brown, Sabrina R.; McConnell, Joseph R. (December 2020). "High elevation ice patch documents Holocene climate variability in the northern Rocky Mountains". Quaternary Science Advances: 16–17. doi:10.1016/j.qsa.2020.100021. ISSN 2666-0334.
  16. Noble et al. 2016, p. 207.
  17. Madsen 2000, p. 161.
  18. Hockett 2015, p. 292.
  19. Oviatt & Shroder 2016, p. 363-364.
  20. Westfall, Robert D; Millar, Constance I (2004-08-11). "Genetic consequences of forest population dynamics influenced by historic climatic variability in the western USA". Forest Ecology and Management. Dynamics and Conservation of Genetic Diversity in Forest Ecology. 197 (1): 160. doi:10.1016/j.foreco.2004.05.011.
  21. Oviatt & Shroder 2016, p. 278.
  22. Ababneh, Linah (2008-09-01). "Bristlecone pine paleoclimatic model for archeological patterns in the White Mountain of California". Quaternary International. The 22nd Pacific Climate Workshop. 188 (1): 63. Bibcode:2008QuInt.188...59A. doi:10.1016/j.quaint.2007.08.041.
  23. Noble et al. 2016, p. 208.
  24. Shuman & Serravezza 2017, p. 74.
  25. Yuan, Koran & Valdez 2013, p. 157.
  26. Liu, Tao; Ji, Lin; Baker, Victor R.; Harden, Tessa M.; Cline, Michael L. (5 February 2020). "Holocene extreme paleofloods and their climatological context, Upper Colorado River Basin, USA". Progress in Physical Geography: Earth and Environment. 44 (5): 13. doi:10.1177/0309133320904038. S2CID 213001302.
  27. Yuan, Koran & Valdez 2013, p. 158.
  28. Wilkins, David E.; Currey, Donald R. (1999-04-01). "Radiocarbon chronology andδ13C analysis of mid-to late-Holocene aeolian environments, Guadalupe Mountains National Park, Texas, USA". The Holocene. 9 (3): 368. Bibcode:1999Holoc...9..363W. doi:10.1191/095968399677728249. ISSN 0959-6836. S2CID 129122964.

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