Early to Late Holocene Surface Exposure Ages From Two Marine‐Terminating Outlet Glaciers in Northwest Greenland

Nares Strait, a major connection between the Arctic Ocean and Baffin Bay, was blocked by coalescent Innuitian and Greenland ice sheets during the last glaciation. This paper focuses on the events and processes leading to the opening of the strait and the environmental response to establishment of the Arctic‐Atlantic throughflow. The study is based on sedimentological, mineralogical and foraminiferal analyses of radiocarbon‐dated cores 2001LSSL‐0014PC and TC from northern Baffin Bay. Radiocarbon dates on benthic foraminifera were calibrated with ΔR = 220±20 years. Basal compact pebbly mud is interpreted as a subglacial deposit formed by glacial overriding of unconsolidated marine sediments. It is overlain by ice‐proximal (red/grey laminated, ice‐proximal glaciomarine unit barren of foraminifera and containing >2 mm clasts interpreted as ice‐rafted debris) to ice‐distal (calcareous, grey pebbly mud with foraminifera indicative of a stratified water column with chilled Atlantic Water fauna and species associated with perennial and then seasonal sea ice cover) glacial marine sediment units. The age model indicates ice retreat into Smith Sound as early as c. 11.7 and as late as c. 11.2 cal. ka BP followed by progressively more distal glaciomarine conditions as the ice margin retreated toward the Kennedy Channel. We hypothesize that a distinct IRD layer deposited between 9.3 and 9 (9.4–8.9 1σ) cal. ka BP marks the break‐up of ice in Kennedy Channel resulting in the opening of Nares Strait as an Arctic‐Atlantic throughflow. Overlying foraminiferal assemblages indicate enhanced marine productivity consistent with entry of nutrient‐rich Arctic Surface Water. A pronounced rise in agglutinated foraminifers and sand‐sized diatoms, and loss of detrital calcite characterize the uppermost bioturbated mud, which was deposited after 4.8 (3.67–5.55 1σ) cal. ka BP. The timing of the transition is poorly resolved as it coincides with the slow sedimentation rates that ensued after the ice margins retreated onto land.

show abstract

“…ka BP (Reusche et al . ) and thus may have occurred after opening of the strait. Core 014 does not have a distinct event at 8.3 cal.…”

Section: Discussionmentioning

confidence: 99%

“…Alternatively, it may be that this 8.3 ka unit was deposited in response to recession of the Humboldt Glacier at 8.3AE1.7 cal. ka BP (Reusche et al 2018) and thus may have occurred after opening of the strait. Core 014 does not have a distinct event at 8.3 cal.…”

Section: Discussionmentioning

confidence: 99%

Retreat of the Smith Sound Ice Stream in the Early Holocene

Jennings

Andrews

Oliver

et al. 2019

Boreas

View full text Add to dashboard Cite

show abstract

“…A synthesis of geological records in the Hudson Bay Lowlands suggests that the Laurentide Ice Sheet was significantly reduced during MIS 3 and grew rapidly toward the LGM (Dalton et al, ). Terrestrial chronologies from southern Greenland during early to late Holocene show that the Greenland ice sheet margins are sensitive to not only long‐term (larger than 1,000 years) but also short‐term (less than 100 years) climate fluctuations (Reusche et al, ). Based on this evidence, we propose that the Northern Hemisphere ice sheets possibly underwent larger variability in response to the millennial‐scale abrupt climate shifts than previously assumed (Stokes et al, ).…”

Section: Discussionmentioning

confidence: 99%

Climate Noise Influences Ice Sheet Mean State

Niu

Lohmann

Gowan

2019

Geophysical Research Letters

View full text Add to dashboard Cite

Evidence from proxy records indicates that millennial‐scale abrupt climate shifts, called Dansgaard‐Oeschger events, happened during past glacial cycles. Various studies have been conducted to uncover the physical mechanism behind them, based on the assumption that climate mean state determines the variability. However, our study shows that the Dansgaard‐Oeschger events can regulate the mean state of the Northern Hemisphere ice sheets. Sensitivity experiments show that the simulated mean state is influenced by the amplitude of the climatic noise. The most likely cause of this phenomenon is the nonlinear response of the surface mass balance to temperature. It could also cause the retreat processes to be faster than the buildup processes within a glacial cycle. We propose that the climate variability hindered ice sheet development and prevented the Earth system from entering a full glacial state from Marine Isotope Stage 4 to Marine Isotope Stage 3 about 60,000 years ago.

show abstract

“…Although an informal tripartite subdivision of the Holocene into early, middle (or mid-) and late phases is widely used, the time intervals vary widely (Table 1) and the terms are often not clearly defined (e.g. Fyfe et al, 2018;Reusche et al, 2018). Practice also varies with respect to the use of lower or upper case for the terms "early," "middle," and "late," sometimes within the same publication.…”

Section: The Holocene Series/epochmentioning

confidence: 99%

Subdividing the Holocene Series/Epoch: formalization of stages/ages and subseries/subepochs, and designation of GSSPs and auxiliary stratotypes

Walker

Head

Lowe

et al. 2019

J Quaternary Science

169

104

View full text Add to dashboard Cite

The Holocene, which currently spans ~11 700 years, is the shortest series/epoch within the geological time scale (GTS), yet it contains a rich archive of evidence in stratigraphical contexts that are frequently continuous and often preserved at high levels of resolution. On 14 June 2018, the Executive Committee of the International Union of Geological Sciences formally ratified a proposal to subdivide the Holocene into three stages/ages, along with their equivalent subseries/subepochs, each anchored by a Global boundary Stratotype Section and Point (GSSP). The new stages are the Greenlandian (Lower/Early Holocene Subseries/Subepoch) with its GSSP in the Greenland NGRIP2 ice core and dated at 11 700 a b2k (before 2000 CE); the Northgrippian (Middle Holocene Subseries/Subepoch) with its GSSP in the Greenland NGRIP1 ice core and dated at 8236 a b2k; and the Meghalayan (Upper/Late Holocene Subseries/Subepoch) with its GSSP in a speleothem from Mawmluh Cave, north‐eastern India, with a date of 4250 a b2k. We explain the nomenclature of the new divisions, describe the procedures involved in the ratification process, designate auxiliary stratotypes to support the GSSPs and consider the implications of the subdivision for defining the Anthropocene as a new unit within the GTS.

show abstract

Early to Late Holocene Surface Exposure Ages From Two Marine‐Terminating Outlet Glaciers in Northwest Greenland

Cited by 23 publications

References 92 publications

Retreat of the Smith Sound Ice Stream in the Early Holocene

Retreat of the Smith Sound Ice Stream in the Early Holocene

Climate Noise Influences Ice Sheet Mean State

Subdividing the Holocene Series/Epoch: formalization of stages/ages and subseries/subepochs, and designation of GSSPs and auxiliary stratotypes

Contact Info

Product

Resources

About