TY - JOUR

T1 - A multimillion-year-old record of Greenland vegetation and glacial history preserved in sediment beneath 1.4 km of ice at Camp Century

AU - Christ, Andrew J.

AU - Bierman, Paul R.

AU - Schaefer, Joerg M.

AU - Dahl-Jensen, Dorthe

AU - Steffensen, Jorgen P.

AU - Corbett, Lee B.

AU - Peteet, Dorothy M.

AU - Thomas, Elizabeth K.

AU - Steig, Eric J.

AU - Rittenour, Tammy M.

AU - Tison, Jean-Louis

AU - Blard, Pierre-Henri

AU - Perdrial, Nicolas

AU - Dethier, David P.

AU - Lini, Andrea

AU - Hidy, Alan J.

AU - Caffee, Marc W.

AU - Southon, John

PY - 2021/3/30

Y1 - 2021/3/30

N2 - Understanding the history of the Greenland Ice Sheet (GrIS) is critical for determining its sensitivity to warming and contribution to sea level; however, that history is poorly known before the last interglacial. Most knowledge comes from interpretation of marine sediment, an indirect record of past ice-sheet extent and behavior. Subglacial sediment and rock, retrieved at the base of ice cores, provide terrestrial evidence for GrIS behavior during the Pleistocene. Here, we use multiple methods to determine GrIS history from subglacial sediment at the base of the Camp Century ice core collected in 1966. This material contains a stratigraphic record of glaciation and vegetation in northwestern Greenland spanning the Pleistocene. Enriched stable isotopes of pore-ice suggest precipitation at lower elevations implying ice-sheet absence. Plant macrofossils and biomarkers in the sediment indicate that paleo-ecosystems from previous interglacial periods are preserved beneath the GrIS. Cosmogenic Al-26/Be-10 and luminescence data bracket the burial of the lower-most sediment between <3.2 +/- 0.4 Ma and >0.7 to 1.4 Ma. In the upper-most sediment, cosmogenic Al-26/Be-10 data require exposure within the last 1.0 +/- 0.1 My. The unique subglacial sedimentary record from Camp Century documents at least two episodes of ice-free, vegetated conditions, each followed by glaciation. The lower sediment derives from an Early Pleistocene GrIS advance. Al-26/Be-10 ratios in the upper-most sediment match those in subglacial bedrock from central Greenland, suggesting similar ice-cover histories across the GrIS. We conclude that the GrIS persisted through much of the Pleistocene but melted and reformed at least once since 1.1 Ma.

AB - Understanding the history of the Greenland Ice Sheet (GrIS) is critical for determining its sensitivity to warming and contribution to sea level; however, that history is poorly known before the last interglacial. Most knowledge comes from interpretation of marine sediment, an indirect record of past ice-sheet extent and behavior. Subglacial sediment and rock, retrieved at the base of ice cores, provide terrestrial evidence for GrIS behavior during the Pleistocene. Here, we use multiple methods to determine GrIS history from subglacial sediment at the base of the Camp Century ice core collected in 1966. This material contains a stratigraphic record of glaciation and vegetation in northwestern Greenland spanning the Pleistocene. Enriched stable isotopes of pore-ice suggest precipitation at lower elevations implying ice-sheet absence. Plant macrofossils and biomarkers in the sediment indicate that paleo-ecosystems from previous interglacial periods are preserved beneath the GrIS. Cosmogenic Al-26/Be-10 and luminescence data bracket the burial of the lower-most sediment between <3.2 +/- 0.4 Ma and >0.7 to 1.4 Ma. In the upper-most sediment, cosmogenic Al-26/Be-10 data require exposure within the last 1.0 +/- 0.1 My. The unique subglacial sedimentary record from Camp Century documents at least two episodes of ice-free, vegetated conditions, each followed by glaciation. The lower sediment derives from an Early Pleistocene GrIS advance. Al-26/Be-10 ratios in the upper-most sediment match those in subglacial bedrock from central Greenland, suggesting similar ice-cover histories across the GrIS. We conclude that the GrIS persisted through much of the Pleistocene but melted and reformed at least once since 1.1 Ma.

KW - Pleistocene

KW - ice core Arctic

KW - climate

KW - ice sheet

U2 - 10.1073/pnas.2021442118

DO - 10.1073/pnas.2021442118

M3 - Journal article

C2 - 33723012

VL - 118

JO - Proceedings of the National Academy of Sciences of the United States of America

JF - Proceedings of the National Academy of Sciences of the United States of America

SN - 0027-8424

IS - 13

M1 - 2021442118

ER -