Amulti-proxy paleolimnological reconstruction of Holocene climate conditions in the Great Basin, United States

a r t i c l e i n f o A sediment core spanning ∼ 7000 cal yr BP recovered from Stella Lake, a small sub-alpine lake located in Great Basin National Park, Nevada, was analyzed for subfossil chironomids (non-biting midges), diatoms, and organic content (estimated by loss-on-ignition (LOI)). Subfossil chironomid analysis indicates that Stella Lake was characterized by a warm, middle Holocene, followed by a cool " Neoglacial " period, with the last two millennia characterized by a return to warmer conditions. Throughout the majority of the core the Stella Lake diatom-community composition is dominated by small, periphytic taxa which are suggestive of shallow, cool, alkaline, oligotrophic waters with extensive seasonal ice cover. A reconstruction of mean July air temperature (MJAT) was developed by applying a midge-based inference model for MJAT (two-component WA-PLS) consisting of 79 lakes and 54 midge taxa (r jack 2 = 0.55, RMSEP = 0.9°C). Comparison of the chironomid-inferred temperature record to existing regional paleoclimate reconstructions suggests that the midge-inferred temperatures correspond well to regional patterns. This multi-proxy record provides valuable insight into regional Holocene climate and environmental conditions by providing a quantitative reconstruction of peak Holocene warmth and aquatic ecosystem response to these changes in the Great Basin, a region projected to experience increased aridity and higher temperatures. Introduction The Earth's globally averaged surface temperature increased ∼ 0.17°C per decade between 1979 and 2005 (Cole et al., 2002; Smith and Reynolds, 2005). This increase in near-surface temperature is spatially heterogeneous with high-latitude and high-elevation regions experiencing greater rates of warming (Diaz and Bradley, 1997; Pepin and Lundquist, 2008). For example, the Intermontane region of the United States has warmed at the rate of 0.40°C per decade between 1979–2005 (Smith and Reynolds, 2005). Projected changes in regional hydroclimatology in the western United States are expected to lead to decreased stream-flow, increased forest fires, and pathogen outbreaks strongly advocates focusing climate change research at regional and local scales to improve our understanding of local and regional climate dynamics, which would provide valuable insight to the possible nature of future conditions and the potential feedbacks that may be important in future warm climate scenarios. The Great Basin of the United States, characterized by a highly variable climate and sensitive to changes in regional hydroclimatology, is such a region (Brown and Comrie, 2004; Diffenbaugh et al., 2008). Alterations to the hydroclimatological regime of the Great Basin will …