Midge-inferred Holocene summer temperatures in Southeastern British Columbia, Canada

Abstract

Using fossil midge stratigraphies, we inferred Holocene summer temperatures at three subalpine lakes in eastern British Columbia. The late-glacial sediment indicated cool conditions, with an abundance of Microspectra atrofasciata/ radialis type fossils at Thunder Lake and Redmountain Lake, and Sergentia at Windy Lake. Sergentia and Tanytarsus lugens/ Corynocera oliveri type were dominant in the early Holocene, together with Chironomus at Redmountain Lake. At Thunder and Windy lakes, the early Holocene was dominated by warm-adapted taxa such as Microtendipes. Quantitative midge-temperature inference models reconstruct a 4 to 8 °C rise in mean July air temperature for Windy and Thunder lakes at the Pleistocene/Holocene transition. Early-Holocene temperatures averaged 3 to 4 °C warmer than those extant today. In contrast, no long-term temperature trend was evident at Redmountain Lake. This site may not reflect actual trends in air temperature due to runoff from a persistent snow pack in the watershed. Comparison of midge and pollen data suggests an inverse relationship between summer temperature and precipitation through the middle to late Holocene.