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

Abstract

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 26Al/10Be 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 26Al/10Be 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. 26Al/10Be 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.

Drivers of phylogenetic structure in Amazonian freshwater fish assemblages

“…These marine incursions have favored the adaptation of several marine lineages to fresh water environment (Bloom & Lovejoy, 2017;Fontenelle et al, 2021;Lovejoy et al, 2006) but also probably led to high extinctions due to the concomitant elimination of freshwater habitats in areas affected by these marine incursions (Oberdorff et al, 2019). In agreement with this last hypothesis, we found a slightly significant negative relationship between ses.MNTD and eastern sub-drainages impacted by the last see level rise during the middle Pleistocene (<1Mya, ~25m) (Christ et al, 2021), meaning that assemblages in these subdrainages are more phylogenetically clustered than expected. This may be due to high extinction rates of lowland freshwater fish species in submerged areas that reduced their overall species richness and diversification processes in the remaining, higher elevation, isolated areas (Oberdorff et al 2019).…”

“…Hoorn et al, 2010) and eastern (e.g. : Christ et al, 2021) parts and on ancient (Eocene to Miocene periods in the West; Pozo and Pebas systems) and more recent (Pleistocene marine incursions in the East) time scales. These marine incursions have favored the adaptation of several marine lineages to fresh water environment (Bloom & Lovejoy, 2017;Fontenelle et al, 2021;Lovejoy et al, 2006) but also probably led to high extinctions due to the concomitant elimination of freshwater habitats in areas affected by these marine incursions (Oberdorff et al, 2019).…”

Retreat and Regrowth of the Greenland Ice Sheet During the Last Interglacial as Simulated by the CESM2‐CISM2 Coupled Climate–Ice Sheet Model

“…Johnsen et al (2001) speculated that the ice retrieved at the bottom of this core may have been deposited during the regrowth of the GrIS at the Camp Century site, having melted away during the early LIG. This suggestion has been reinforced by thermoluminescence (TL) dating of sediments at the bottom of the core (Christ et al, 2021) which indicates ice-free conditions sometime prior to 45 ka. The southern dome of the GrIS in our simulation reaches its minimum extent at 121.9 ka, before regrowing and reattaching to the northern dome at 120.5 ka.…”

Empirical Evidence for Latitude and Altitude Variation of the In Situ Cosmogenic 26Al/10Be Production Ratio

“…Bierman et al [2] demonstrated the utility of the paired-nuclide approach for calculating minimum total durations of exposure and burial for complex glacial histories in temperate regions-those involving multiple periods of advance and retreat. Investigations of complex glacial histories continue to be a common application of 26 Al/ 10 Be [32,33], including cases with minimal glacial erosion due to cold-based ice cover [4,34] and glacial histories inferred from marine sediment records [35,36]. 26 Al/ 10 Be has also been used to evaluate long-term erosion rates in arid regions [37], histories of tectonic uplift [38], river incision [5,6], and paleosol burial [39,40].…”