Holocene seasonal variability inferred from multiple proxy records from Crevice Lake, Yellowstone National Park, USA

Abstract

Stone, Jeffery R.; Power, Mitchell J.; Rosenbaum, Joseph R.; Pierce, Kenneth L.; and Bracht-Flyr, Brandi B., "Holocene seasonal variability inferred from multiple proxy records from Crevice Lake, Yellowstone National Park, USA" (2012 A 9400-yr-old record from Crevice Lake, a semi-closed alkaline lake in northern Yellowstone National Park, was analyzed for pollen, charcoal, geochemistry, mineralogy, diatoms, and stable isotopes to develop a nuanced understanding of Holocene environmental history in a region of northern Rocky Mountains that receives both summer and winter precipitation. The limited surface area, conical bathymetry, and deep water (> 31 m) of Crevice Lake create oxygen-deficient conditions in the hypolimnion and preserve annually laminated sediment (varves) for much of the record. Pollen data indicate that the watershed supported a closed Pinus-dominated forest and low fire frequency prior to 8200 cal yr BP, followed by open parkland until 2600 cal yr BP, and open mixed-conifer forest thereafter. Fire activity shifted from infrequent standreplacing fires initially to frequent surface fires in the middle Holocene and stand-replacing events in recent centuries. Low values of δ 18O suggest high winter precipitation in the early Holocene, followed by steadily drier conditions after 8500 cal yr BP. Carbonate-rich sediments before 5000 cal yr BP imply warmer summer conditions than after 5000 cal yr BP. High values of molybdenum (Mo), uranium (U), and sulfur (S) indicate anoxic bottom-waters before 8000 cal yr BP, between 4400 and 3900 cal yr BP, and after 2400 cal yr BP. The diatom record indicates extensive water-column mixing in spring and early summer through much of the Holocene, but a period between 2200 and 800 cal yr BP had strong summer stratification, phosphate limitation, and oxygen-deficient bottom waters. Together, the proxy data suggest wet winters, protracted springs, and warm effectively wet summers in the early Holocene and less snowpack, cool springs, warm dry summers in the middle Holocene. In the late Holocene, the region and lake experienced extreme changes in winter, spring, and summer conditions, with particularly short springs and dry summers and winters during the Roman Warm Period (~2000 cal yr BP) and Medieval Climate Anomaly (1200-800 cal yr BP). Long springs and mild summers occurred during the Little Ice Age, and these conditions persist to the present. Although the proxy data indicate effectively wet summer conditions in the early Holocene and drier conditions in the middle and late Holocene, none point specifically to changes in summer precipitation as the cause. Instead, summer conditions were governed by multi-seasonal controls on effective moisture that operated over multiple time scales.

Holocene fire occurrence and alluvial responses at the leading edge of pinyon–juniper migration in the Northern Great Basin, USA

“…This mid-Holocene peak is recorded in other alluvial charcoal records in central Idaho (Pierce et al, 2004;Riley, 2012), and in lake charcoal records throughout the Northern Rocky Mountains (e.g., Power et al, 2011), likely in response to regional drought conditions ( Fig. 6; Murchison, 1989;Louderback and Rhode, 2009;Shuman et al, 2009;Corbett and Munroe, 2010;Whitlock et al, 2012).…”

Diatom Seasonality and Sedimentation in a Subtropical Alpine Lake (Lugu Hu, Yunnan-Sichuan, Southwest China)

“…Increases in the relative abundances of small Cyclotella species are often interpreted as signals for warming-induced changes in the length of ice-free season or depth of mixed layer (Winder et al, 2009). Depth of the mixed surface layer and hence the stability of thermal stratification influences Cyclotella abundance; C. ocellata, for example, is associated with shallower summer mixing depths (Whitlock et al, 2012). Nutrient availability, however, is an important aspect of the response of Cyclotella species to changes in lake mixing depths (Saros et al, 2012).…”

Climate Change

“…Most prehistoric fires were likely mixed-or high-severity events, given the persistence of lodgepole pine. Other studies of Yellowstone show the occurrence of infrequent large fires during the Little Ice Age (1600-1900 AD), and fewer and likely small fire events during the Medieval Climate Anomaly (800-1200 AD) (Meyer et al, 1995;Pierce et al, 2004;Whitlock et al, 2012). By contrast, an analysis of postfire sediment deposits in alluvial fans in ponderosa pine (Pinus ponderosa) forests in southern Idaho revealed large, severe-fire events well above recent levels during a warm period from 1050 to 650 cal year BP (Pierce et al, 2004).…”