H. H. Lamb identified the Medieval Warm Period (MWP) as a prolonged interval of warmth in northern Europe from AD 900 – 1200 (1050 – 750) cal yr BP (1965). Data from elsewhere in the Northern Hemisphere indicate that there may have been several pulses of warmth, and the timing of these changes varies significantly by location. The Little Ice Age (LIA) was a period of modest cooling in northern Europe from AD 1400 – 1800 (550 – 150 cal yr BP). Outside of northern Europe, evidence for periods of cooling occurs from AD 1200 – 1900 (750 – 50 cal yr BP). The apparent temporal and spatial variability of both the MWP and the LIA suggests that more research is necessary to determine how these climate anomalies extended across the Northern Hemisphere.
This study examines the vegetation history of Many Glacier Valley using pollen extracted from a sediment core taken from Swiftcurrent Lake (SWF) in Glacier National Park, MT. Pollen is used to create a vegetation reconstruction focusing on the past 1200 years, which includes both the MWP and LIA. Changes in vegetation through time reflect vegetation’s response to climate, specifically temperature and precipitation, and thus can be used to broadly reconstruct past climate. Evidence from pollen indicates that the region surrounding SWF during the MWP was likely drier and warmer than present climate, and more moist and cool during the LIA. This is consistent with other results from the Western United States.
Locatelli, Emma R., "Vegetation History of the Late Holocene in East Glacier National Park, Montana: A Paleoenvironmental Study" (2011). Geology Honors Projects. Paper 9.
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