Abstract
Predicting the response of the Greenland Ice Sheet to future climate change presents a major challenge to climate science. Paleoclimate data from Greenland can provide empirical constraints on past cryospheric responses to climate change, complementing insights from contemporary observations and from modeling. Here we examine sedimentary records from five lakes near Jakobshavn Isbræ in central West Greenland to investigate the timing and magnitude of major Holocene climate changes, for comparison with glacial geologic reconstructions from the region. A primary objective of this study is to constrain the timing and magnitude of maximum warmth during the early to middle Holocene positive anomaly in summer insolation. Temperature reconstructions from subfossil insect (chironomid) assemblages suggest that summer temperatures were warmer than present by at least 7.1 ka (the beginning of the North Lake record; ka = thousands of years before present), and that the warmest millennia of the Holocene occurred in the study area between 6 and 4 ka. Previous studies in the Jakobshavn region have found that the local Greenland Ice Sheet margin was most retracted behind its present position between 6 and 5 ka, and here we use chironomids to estimate that local summer temperatures were 2-3 °C warmer than present during that time of minimum ice sheet extent. As summer insolation declined through the late Holocene, summer temperatures cooled and the local ice sheet margin expanded. Gradual, insolation-driven millennial-scale temperature trends in the study area were punctuated by several abrupt climate changes, including a major transient event recorded in all five lakes between 4.3 and 3.2 ka, which overlaps in timing with abrupt climate changes previously documented around the North Atlantic region and farther afield at ∼4.2 ka.
Original language | English (US) |
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Pages (from-to) | 87-100 |
Number of pages | 14 |
Journal | Quaternary Science Reviews |
Volume | 59 |
DOIs | |
State | Published - 2013 |
Funding
Kristen Bartucci, Clayton Brengman, Otomo Darko, and Humza Shaikh contributed to laboratory analyses. Darrell Kaufman and Katherine Sides (Northern Arizona University) provided biogenic silica analyses. Chris Kuzawa, William Philipps, Heather Stewart, and Nicolás Young assisted with field work. We thank CH2M Hill Polar Services, including Robin Abbott, Mark “Sparky” Begnaud, and Ed Stockard, and the New York Air National Guard 109th Airlift Wing for help with field logistics. The Greenland Bureau of Minerals and Petroleum granted permission to collect samples. Chris Kuzawa and two anonymous reviewers provided helpful suggestions for improving this manuscript. This work was funded by the U.S. National Science Foundation ( ARC-0909347 to Axford, ARC-0909334 to Briner, and BCS-0752848 to Briner and Axford) and the Initiative for Sustainability and Energy at Northwestern University (ISEN) .
Keywords
- Chironomidae
- Greenland
- Holocene thermal maximum
- Jakobshavn
- Lake sediments
- Neoglaciation
- Paleoclimate
ASJC Scopus subject areas
- Global and Planetary Change
- Ecology, Evolution, Behavior and Systematics
- Archaeology
- Archaeology
- Geology