University of Nebraska - Lincoln DigitalCommons@University of Nebraska - Lincoln USGS Staff -- ubP lished Research US Geological Survey 1990 Paleoclimatic implications of the high stand of Lake Lahontan derived from models of evaporation and lake level S Hostetler US Geological Survey Larry Benson University of Colorado at Boulder, [email protected] Follow this and additional works at: http://digitalcommons.unl.edu/usgsstaffpub Hostetler, S and Benson, Larry, "Paleoclimatic implications of the high stand of Lake Lahontan derived from models of evaporation and lake level" (1990). USGS Staff -- Published Research. 790. http://digitalcommons.unl.edu/usgsstaffpub/790 This Article is brought to you for free and open access by the US Geological Survey at DigitalCommons@University of Nebraska - Lincoln. It has been accepted for inclusion in USGS Staff -- ubP lished Research by an authorized administrator of DigitalCommons@University of Nebraska - Lincoln. Climate Dynamics (1990) 4:207-217 ( lima|¢ Dynamics © Springer-Verlag 1990 Paleoclimatic implications of the high stand of Lake Lahontan derived from models of evaporation and lake level S Hostetler and LV Benson US Geological Survey, National Center for Atmospheric Research, P.O. Box 3000ML, Boulder, Co 80301-3000, USA Received December 4, 1989/Accepted May 7, 1990 Abstract. Based on previous climate model simulations models is coarse (the NCAR Community Climate Mod- of a split of the polar jet stream during the late Pleisto- el, CCMO, used by Kutzbach and Gutter has a 4.4 ° la- cene, we hypothesize that (1) 20-13.5 ka BP, season-to- titude grid), (2) the boundary conditions (e.g., sea sur- season variation in the latitudinal maximum of the jet face temperatures and the size and height of the ice stream core led to enhanced wetness in the Great Basin, sheet) in the modeling experiments were prescribed, and (2) after 13.5 ka BP, northward movement of the jet and (3) the models can have deficiencies that may lead stream resulted in increased aridity similar to today. to misplacement of the simulated jet stream, these sim- We suggest that the enhanced effective wetness was due ulations all indicate that during the late Pleistocene to increased precipitation combined with an energy- the polar jet stream probably was split around the limited reduction in evaporation rates that was caused North American continental ice sheet. (The split in the by increased summer cloud cover. A physically based jet stream appears to have been caused by the height thermal evaporation model was used to simulate evapo- and size of the ice sheet and associated changes in at- ration for Lake Lahontan under various hypothesized mospheric heating and cooling that developed over the paleoclimates. The simulated evaporation rates, to- ice.) A connection between late Pleistocene change in gether with hypothetical rates of precipitation and dis- atmospheric circulation and the hydrologic budgets of charge, were input to a water balance model of Lake the closed Great Basin lake systems (Fig. 1) has been Lahontan. A 42% reduction in evaporation rate, com- suggested by Antevs (1948), Benson and Thompson bined with maximum historical rates of precipitation (1987a, b), and Lao and Benson (1988). Those authors (1.8 times the mean annual rate) and discharge (2.4 hypothesized that a southern displacement of the jet times the mean annual rate), were sufficient to maintain stream by the continental ice sheet may have led to wet- Lake Lahontan at its 20-15 ka BP level. When discharge ter conditions in the Great Basin. was increased to 3.8 times the present-day, mean an- In this study we tested the hypothesis that change in nual rate, the ~ 13.5 ka BP maximum level of Lake La- the position of the polar jet stream was the primary hontan was attained within 1400 years. A 135-m drop cause of the last late Pleistocene rise and fall of the from the maximum level to Holocene levels was simu- large Great Basin lake systems. We used a physically lated within 300 years under the imposition of the pres- based lake model to simulate changes in lake tempera- ent-day hydrologic balance. ture and evaporation that occurred in response to change in the lake surface energy balance and in a small set of atmospheric parameters. A sensitivity anal- ysis of evaporation was done by using plausible late Introduction Pleistocene air temperature and cloud cover that was assumed to have accompanied displacement of the po- Atmospheric general circulation models (AGCMs) lar jet stream. The input data set used in the sensitivity have been used to simulate synoptic-scale patterns of analysis consisted of proxy indicators of air tempera- past atmospheric circulation over western North Amer- ture and an analogue for cloud cover related to the ica (Manabe and Broccoli 1985; Kutzbach and Guetter present-day jet stream. Input data sets for the lake level 1986; Rind 1987). Although (1) the resolution of these simulations consisted of evaporation rates calculated in the sensitivity analysis and historical along with hypo- thetical rates of precipitation and streamflow. The si- mulated lake level trajectories are compared with the late Pleistocene chronology of Lake Lahontan (Benson Offprint requests to: S. Hostetler et al., in press). 208 Hostetler and Benson: Paleoclimatic implications of the level of Lake Lahontan 1210 1190 1170 1150 1130 111o I I [ I 43 o LAKE BONNEVILLE \ N iDAHO ;EVADA GREA T SALT ' LAKE L,L LAKE :i:!:i:!:?:?$i:i:i:i 41 o 0 390 J 0 I LL .9 ,:3 UTAH \ 37 ° PHYSIOGRAPHIC BOUNDARY OF GREAT BASIN EXISTING BODIES OF WATER FORMER LATE- 35 o WISCONSIN AGE BODIES OF WATER I I I I 0 400 KILOMETERS I ' ' ' JI 1 0 200 MILES Fig. 1. Size and location of late Pleistocene lakes in the Great Basin Interpretation of AGCM jet-stream simulations southern branch of the split jet stream (AGCM sigma level 0.5; -500 mb) was at -33°N latitude (Fig. 2a). The simulations of Kutzbach and Guetter (1986) indi- Between 15 and 12 ka BP, the mean position of the cate that 18-15 ka BP, the mean winter (perpetual Jan- winter jet stream core moved northward in response to uary) position of the core (maximum velocity) of the a prescribed reduction in the size and height of the con- Hostetler and Benson: Paleoclimatic implications of the level of Lake Lahontan 209 a JANUARY b JULY 86.6N " 86.6N 77,8 -" -" -" ...... 77.8 " 68.9 -'-) --> --> "--> "-~ "-~ ~ ~ "-~ "-~========~,~===============~ ....... 68 9 • :.:.... - . ....-,. ....- z 600. .... "~ "~ -~ "~ "~ "~ -~ -~ " 600 ~ " ~ ~ ~ "~ "~ -~ ....-..-'::~:" "~ ~ ~ 51.1 -~ ~ " " " v.,..,-:~:" ~" " " P ' uJ 51.1 " - ~ -~ -~, ..................~.i:iii!:~i!::i::!::~!iiii~i!ii!~:i:i: - .............. :i:i: .. ~-2/t...-'~ .m p p I /~::!:~:i::; ,T P ~' .~ I ;' C3 "*' ~ ~ "t" ~ ..T~::[:i:::"~' ~ ~ ~ ~ ~ "~ • :,:.:.:.: :.:; :>..... .-...... 42.2 .... ...,.; .,, .,- .:.:::p 7 7 .~ ~ .~ 7 42,2 ~ ~ ~ ~ , ...-.,..~iiii:!:'Lg' ..,...,, "* "~ "~ "~ "~ ~ • • ..:.:,:,: ::::::::::::::::::::::: ~i:i:i:,:~:::::;::4,.~.::-. ,an> .-> ~ ~ ~ .~ ~ --~ ..~ .-~ 33.3 > " -" -" ,a, .,, , .... , ,,, 333 .__> ._~ __> ._~ .~ ~ .., _. _.. _~ _~ _~ .+ J 24.4 24.4 -* ~ ~ ~ "* "~" ~ ~' ~ ~ ~ ~ "* ~5.6 - 15.6 " • ~'= 20 ms 4 6.7N " 6.7N ....... --> =10ms 4 18 15 12 9 6 3 0 18 15 12 9 6 3 0 TIME (kyr BP) TIME (kyr BP) Fig. 2a, b. Latitude-time diagram of January (a) and July (b) represented by the maximum vector wind). Data values are aver- mean upper level winds (at the 500-mb level) from 18 to 0 ka BP ages of three columns of western North America grid cells (at simulated by the NCAR Community Climate Model (CCMO). 127.5 °, 120.0°, and 112.5° W). Solid horizontal lines indicate the Values were simulated at 3-ka intervals from 18 to 0 ka BP, values approximate latitudinal extent of the Great Basin (data from between the simulations were interpolated, Stippling indicates the Kutzbach and Guetter 1986) latitude of the core of the southern branch of the jet stream (as tinental ice sheet. Although no model simulation was Pyke 1972; Bryson and Hare 1977; Hare and Hay carried out for 13.5 ka BP, by interpolation the simu- 1977). If, during the late Pleistocene, the climatic char- lated mean position of the winter jet stream core moved acteristics of the jet stream were similar to those of to- northward to ~ 37 ° N. After 12 ka BP, the ice sheet was day, then the positioning of the jet stream over the small enough to allow the two branches of the winter Great Basin at that time should have led to relatively jet stream to recombine and remain north of the Great cooler and wetter conditions in that region. Basin. The presence of cold, late Pleistocene air tempera- In the summer (perpetual July) of 18 ka BP, the sim- tures over the Great Basin has been previously hypo- ulated mean position of the core of the southern thesized. Evidence in support of colder temperatures branch of the summer jet stream was -45 ° N latitude has been reported in studies of nivation features (Doh- (Fig. 2b). By interpolation, by 13.5 ka BP the mean po- renwend 1984) and pack rat middens (Thompson and sition of the jet stream core moved south of its 18 ka BP Mead 1982; Thompson 1984). These studies suggest position. After 9 ka BP, the simulated mean position of that during the late Pleistocene, Great Basin air temper- the summer jet stream was north of the Great Basin. atures were at least 5-7 ° C colder than today. Existence Today, along the west coast of North America, the of a cold period also is supported by the presence of seasonal location of the jet stream core varies by ~ 16 ° ice-rafted material in a 75-m core taken from the north of latitude between the mean winter (42 ° N) and sum- shore of Pyramid Lake (L Benson and G Kukla, unpub- mer (58 ° N) positions (Bryson and Hare 1977).