Stalagmite records of hydroclimate in central California during termination 1

Abstract

a b s t r a c tThe last deglaciation is marked by large and abrupt hydroclimatic changes in the Great Basin and the American Southwest. However, comparatively little is known about how hydroclimate varied on the western side of the Sierra Nevada. We present new evidence for abrupt changes in precipitation amount in the central Sierra Nevada during the last deglaciation. Our new record from McLean's Cave overlaps with a previously published record from nearby Moaning Cave (Oster et al., 2009), and extends the record of hydroclimatic change in the region through Heinrich Stadial 1. McLean's Cave speleothem d 18 O, d 13 C, Mg/Ca, and Sr/Ca indicate a shift to drier conditions at the beginning of Heinrich Stadial 1 from 16.1to 17.5 ka followed by wetter conditions at the end of Heinrich Stadial 1 when the majority of Great Basin lakes reached their deglacial highstands. During the last deglaciation, coincident shifts in the Moaning and McLean's Cave proxy records indicate drier conditions in the western Sierra Nevada during millennial-scale intervals of warming at high latitudes such as the B€ olling and Aller€ od, and wetter conditions during cooler intervals such as the Older and Younger Dryas. Thus, the Sierra Nevada speleothem records are consistent with other regional records that document increased winter rainfall during millennial-scale cold periods of the last deglaciation. However, regional differences exist in the hydroclimatic response to the Younger Dryas, with central Californian and interior southwestern sites indicating an increase in winter storms that is not apparent in southern California. Dynamic simulations of atmospheric circulation indicate that wetter conditions during the Younger Dryas relative to the B€ olling at McLean's Cave may have resulted from a stronger storm track in the north Pacific at the latitude of northern California.

Climate response to the 8.2 ka event in coastal California

“…Variable dissolution of limestone and dolomite marble has also been interpreted as an important control on speleothem Mg/Ca in caves within the Sierra Nevada foothills in California where speleothem Mg/Ca and Sr/Ca show negative correlations 24, 37 , similar to what is noted in WMC1. Furthermore, the elongated columnar crystal fabric observed throughout WMC1 is common in speleothems precipitating from seepage waters that have interacted with dolomite or other Mg-rich rocks 11, 12 .…”

“…Previous speleothem and cave drip water studies from Oregon 20, 22 and central California 23, 24 (Fig. 1) attributed water and speleothem δ 18 O variability to changes in local atmospheric temperature at the time of precipitation and moisture sources.…”

“…As shown below, the new record suggests that the 8.2 ka event was associated with a brief period of wetter conditions, potentially arising from increased storminess, and demonstrates a near synchronous climatic response to this event on both sides of the Pacific.

Figure 1Location of White Moon Cave (star) and seasonality of modern precipitation in surrounding region. Boxes show locations of other Holocene speleothem records from the western United States: OC = Oregon Caves 20 , MC/ML = Moaning and McLean’s Caves 24 ; LC = Lehman Caves 28 . Circle shows location of ODP core 1019 10 .

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Human-induced changes in the distribution of rainfall

“…Stalagmites from caves in central and southern California ( 41 ), New Mexico ( 42 ), and Nevada ( 43 ) also record peak winter moisture during this interval. In the case of Lake Lahontan, the evidence comes from a camel bone found in a back-beach deposit associated with its highest shoreline ( 44 ).…”

The hydrologic record of karst systems: linking soil moisture to the carbon isotope signatures of soils above the Blue Spring cave system

“…Several aspects have been proposed explaining the variations in speleothem d 13 C. Some studies have suggested that the respiration record is not totally erased, and thus may serve as an indicator of past changes in the hydrologic cycle (e.g. Oster et al 2015). However, a recent study suggests that such changes can only be recorded in the speleothems when environments are described by low mean annual precipitation and temperature (Breecker 2017).…”