A 2000-year varve-based climate record from the central Brooks Range, Alaska

bird, b.w., abbott, m.b., kutchko, b., and finney, b.p.

Abstract

Study Location

Blue Lake is a small glacial-fed lake that is located in the central Brooks Range of Alaska at 1275 meters above sea level along the Continental Divide. The lake is ~41 km east of Atigun Pass, the northern most pass on the Dalton Highway, which contains the closest weather station. Surface and long cores were collected from Blue Lake in August of 1999 and July of 2006.

Climate Proxy

Varve thickness:

• Varve thickness in Blue Lake is correlated with summer (June-July-August; JJA) temperature at Atigun Pass. Warm (cool) summers result in increased (decreased) snow and glacial melt, which increases (decreases) the amount of sediment delivered to the lake, resulting increasing (decreasing) varve thicknesses. Downcore trends in varve thickness are, therefore, interpreted to reflect past temperature variability.

Results

We reconstructed average JJA temperatures in the central Brooks Range for the past 1275 years using the modern varve-summer temperature relationship. JJA temperatures were ~1.0°C cooler than the modern (1950-2005 AD average) during the Little Ice Age. Two warm periods prior to the LIA are noted between 1500-1620 AD and 1350-1450 (0.5°C and 0.4°C cooler than today, respectively). Two distinct cool episodes between 980-1030 AD and 1260-1350 AD were 1.6°C and 1.1°C cooler than modern.

References

• Anderson L, Abbott MB, Finney BP, Burns SJ (2007) Late Holocene moisture balance variability in the southwest Yukon Territory, Canada. Quat. Sci. Rev. 26: 130-141
• Ellis JM, Calkin PE (1984) Chronology of Holocene glaciation, central Brooks Range, Alaska. Geological Society of America Bulletin 95: 897-912

Related websites

• Broxton Bird's website
• Mark Abbott's website