Neopluvial is a term referring to a phase of wetter and colder climate that occurred during the late
Holocene
The Holocene ( ) is the current geological epoch. It began approximately 11,650 cal years Before Present (), after the Last Glacial Period, which concluded with the Holocene glacial retreat. The Holocene and the preceding Pleistocene togeth ...
in the
Western United States
The Western United States (also called the American West, the Far West, and the West) is the region comprising the westernmost states of the United States. As American settlement in the U.S. expanded westward, the meaning of the term ''the We ...
. 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
The Holocene ( ) is the current geological epoch. It began approximately 11,650 cal years Before Present (), after the Last Glacial Period, which concluded with the Holocene glacial retreat. The Holocene and the preceding Pleistocene togeth ...
, causing the levels of lakes in the
Great Basin to increase and previously dry lakes and
spring
Spring(s) may refer to:
Common uses
* Spring (season)
Spring, also known as springtime, is one of the four temperate seasons, succeeding winter and preceding summer. There are various technical definitions of spring, but local usage of ...
s to refill.
It has been observed in
Great Salt Lake,
Fallen Leaf Lake,
Lake Cochise, the
Mojave Desert
The Mojave Desert ( ; mov, Hayikwiir Mat'aar; es, Desierto de Mojave) is a desert in the rain shadow of the Sierra Nevada mountains in the Southwestern United States. It is named for the indigenous Mojave people. It is located primarily ...
,
Mono Lake
Mono Lake ( ) is a saline soda lake in Mono County, California, formed at least 760,000 years ago as a terminal lake in an endorheic basin. The lack of an outlet causes high levels of salts to accumulate in the lake which make its water a ...
,
Owens Lake
Owens Lake is a mostly dry lake in the Owens Valley on the eastern side of the Sierra Nevada in Inyo County, California. It is about south of Lone Pine, California. Unlike most dry lakes in the Basin and Range Province that have been dry for ...
,
Pyramid Lake,
San Luis Lake,
Silver Lake,
Summer Lake,
Tulare Lake
Tulare Lake () ( Spanish: ''Laguna de Tache'', Yokuts: ''Pah-áh-su'') is a freshwater dry lake with residual wetlands and marshes in the southern San Joaquin Valley, California, United States. After Lake Cahuilla disappeared in the 17th century ...
,
Walker Lake and
Winnemucca Lake
Winnemucca Lake is a dry lake bed in northwest Nevada that features the oldest known petroglyphs in North America. Located astride the border between Washoe and Pershing counties, it was a shallow lake until the 1930s, but was dried when a d ...
.
During the Neopluvial, the Great Salt Lake became fresher, and Pyramid Lake reached a water level of above sea level.
Walker Lake, Owens Lake and Mono Lake experienced their highest Holocene water levels,
with the volumes of the latter two lakes more than doubling.
Likewise water levels in
Lake Tahoe rose to the point of overflowing into the
Truckee River
The Truckee River is a river in the U.S. states of California and Nevada. The river flows northeasterly and is long.U.S. Geological Survey. National Hydrography Dataset high-resolution flowline dataThe National Map accessed October 20, 2012 Th ...
. Silver Lake in the Mojave Desert formed a perennial lake and vegetation was more widespread in the
Little Granite Mountains.
Summer Lake rose above its present-day level to an elevation of ,
although it was not as high as during the mid-Holocene.
Water levels rose in Tulare Lake as well.
In the
White Mountains,
meadow
A meadow ( ) is an open habitat, or field, vegetated by grasses, herbs, and other non- woody plants. Trees or shrubs may sparsely populate meadows, as long as these areas maintain an open character. Meadows may be naturally occurring or arti ...
s formed during the Neopluvial.
Ice patches in the
Beartooth Mountains
The Beartooth Mountains are located in south central Montana and northwest Wyoming, U.S. and are part of the Absaroka-Beartooth Wilderness, within Custer, Gallatin and Shoshone National Forests. The Beartooths are the location of Granite Peak, ...
and
glacier
A glacier (; ) is a persistent body of dense ice that is constantly moving under its own weight. A glacier forms where the accumulation of snow exceeds its ablation over many years, often centuries. It acquires distinguishing features, such as ...
s grew in the Sierra Nevada,
sagebrush
Sagebrush is the common name of several woody and herbaceous species of plants in the genus '' Artemisia''. The best known sagebrush is the shrub '' Artemisia tridentata''. Sagebrushes are native to the North American west.
Following is an al ...
steppe,
green Mormon tea and other vegetation expanded in the Great Salt Lake region,
marsh
A marsh is a wetland that is dominated by herbaceous rather than woody plant species.Keddy, P.A. 2010. Wetland Ecology: Principles and Conservation (2nd edition). Cambridge University Press, Cambridge, UK. 497 p Marshes can often be found a ...
es expanded in the central and northern
Great Basin,
mammal communities in the
Lake Bonneville
Lake Bonneville was the largest Late Pleistocene paleolake in the Great Basin of western North America. It was a pluvial lake that formed in response to an increase in precipitation and a decrease in evaporation as a result of cooler temperature ...
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 ungulate
The even-toed ungulates (Artiodactyla , ) are ungulates—hoofed animals—which bear weight equally on two (an even number) of their five toes: the third and fourth. The other three toes are either present, absent, vestigial, or pointing poster ...
s, and
tree line
The tree line is the edge of the habitat at which trees are capable of growing. It is found at high elevations and high latitudes. Beyond the tree line, trees cannot tolerate the environmental conditions (usually cold temperatures, extreme snow ...
s dropped, with the lower limit of wooden vegetation penetrating into deserts.
Counterintuitively, higher tree line elevations in the
Lake Bonneville
Lake Bonneville was the largest Late Pleistocene paleolake in the Great Basin of western North America. It was a pluvial lake that formed in response to an increase in precipitation and a decrease in evaporation as a result of cooler temperature ...
area occurred during the Neopluvial, which may indicate warmer summers.
In the
Owens Valley
Owens Valley ( Numic: ''Payahǖǖnadǖ'', meaning "place of flowing water") is an arid valley of the Owens River in eastern California in the United States. It is located to the east of the Sierra Nevada, west of the White Mountains and Iny ...
region, during the Neopluvial the human population became more sedentary and trans-
Sierra Nevada trade became established ("Newberry"/"Middle Archaic Period").
Population around
Lake Alvord increased during this time and lasted even after the Neopluvial had ended there.
Chronology
The beginning of the Neopluvial occurred about 6,000 years
before present
Before Present (BP) years, or "years before present", is a time scale used mainly in archaeology, geology and other scientific disciplines to specify when events occurred relative to the origin of practical radiocarbon dating in the 1950s. Becau ...
, but did not occur everywhere at the same time:
* The Neopluvial occurred between 4,000 and 2,000 years before present in the
Carson Sink
Carson Sink is a playa in the northeastern portion of the Carson Desert in present-day Nevada, United States of America, that was formerly the terminus of the Carson River. Today the sink is fed by drainage canals of the Truckee-Carson Irrigat ...
. The Neopluvial in the
Lake Lahontan
Lake Lahontan was a large endorheic Pleistocene lake of modern northwestern Nevada that extended into northeastern California and southern Oregon. The area of the former lake is a large portion of the Great Basin that borders the Sacramento Rive ...
basin ended about 2,000 years ago.
* In Fallen Leaf Lake, the Neopluvial occurred 3,700 years before present in Fallen Leaf Lake. The end occurred 3,650 years before present;
after that point precipitation became more irregular until the onset of the
Little Ice Age about 3,000 years later.
* Its occurrence is dated between 5,100 and 2,650 years before present in the central-northern Great Basin,
* 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.
* It took place between 3,000 and 4,000 years before present in Lake Cochise.
* It occurred between 4,000 and 2,500 years before present in the Mojave Desert.
* 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.
* 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.
* In the Summer Lake area, the Neopluvial is dated to have occurred between 4,000 and 1,900 years ago.
* Rising water levels in Lake Tahoe drowned trees between 4,800 and 5,700 years before present.
* In Tulare Lake, the Neopluvial lasted between 4,500 and 2,800 years before present; after that a severe
drought
A drought is defined as drier than normal conditions.Douville, H., K. Raghavan, J. Renwick, R.P. Allan, P.A. Arias, M. Barlow, R. Cerezo-Mota, A. Cherchi, T.Y. Gan, J. Gergis, D. Jiang, A. Khan, W. Pokam Mba, D. Rosenfeld, J. Tierney, an ...
occurred.
Related events
The Neopluvial is in part correlative to the
Neoglacial, and might have been caused by a change in winter conditions over the
North Pacific
The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean (or, depending on definition, to Antarctica) in the south, and is bounded by the continen ...
. 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. Strengthening
ENSO variability, a cooling of the North Pacific and a southward shift of the Pacific
jet stream also coincided with the Neopluvial.
The neopluvial resembles the
Pluvial
In geology and climatology, a pluvial is either a modern climate characterized by relatively high precipitation or an interval of time of variable length, decades to thousands of years, during which a climate is characterized by relatively high ...
period that occurred in western North America during the late
Last Glacial Maximum, but was much weaker than the LGM wet period.
Terminology
The term "neopluvial" was coined in 1982 and originally referred to high lake levels in Summer Lake.
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
Texas (, ; Spanish: ''Texas'', ''Tejas'') is a state in the South Central region of the United States. At 268,596 square miles (695,662 km2), and with more than 29.1 million residents in 2020, it is the second-largest U.S. state by ...
, potentially linked to a stronger
monsoon
A monsoon () is traditionally a seasonal reversing wind accompanied by corresponding changes in precipitation but is now used to describe seasonal changes in atmospheric circulation and precipitation associated with annual latitudinal osci ...
or to the neopluvial of the western US.
References
Sources
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{{refend
Climate of North America
History of climate variability and change
Holocene North America