Pulsebeat of early Holocene glaciation in Baffin Bay from high-resolution beryllium-10 moraine chronologies. (15th October 2021) - Young, Nicolás E.
Abstract: Beryllium-10 has become the premiere cosmogenic nuclide for quantifying Earth-surface process. Routine measurement of 10 Be at the ≤ 2–3% precision level, coupled with precise 10 Be production-rate calibrations, now allow for 10 Be-based records of glacier and ice-sheet change to be reliably compared to independent records of climate variability. Here, we review efforts over the last 10+ years to characterize the Holocene behavior of ice sheets and glaciers fringing Baffin Bay using in situ 10 Be. Hundreds of 10 Be measurements present a detailed picture of ice-margin migration through the early Holocene. Widespread net deglaciation was interrupted by ice-margin readvances or stillstands, marked by modes of moraine deposition, near the end of the Younger Dryas (12.9–11.7 ka BP), 10.4–10.2 ka BP, 9.3 ka BP, and 8.2 ka BP, with perhaps additional widespread moraine deposition occurring ca. 9.7 ka BP and 7.3 ka BP. Modes of moraine deposition encompass independent and glaciologically distinct ice masses – the Greenland and Laurentide ice sheets and local alpine glaciers situated on Baffin Island and western Greenland – providing a robust, albeit discontinuous, record of widespread climatic changes in the Baffin Bay region in the early Holocene. Periods of glacier advance coincide with abrupt cooling events documented in Summit Greenland ice cores indicating that i) Baffin Bay ice masses largely followed the pattern of temperature change displayed in Greenland ice cores, ii) abrupt cooling events were of sufficient magnitude and duration to briefly synchronize the behavior of independent and glaciologically distinct ice masses across Baffin Bay despite varying degrees of dynamical influence, and iii) centennial-scale synchronization of ice masses requires that abrupt temperature changes recorded at Summit Greenland also occurred during the summertime within glacier ablation zones. Advancements in 10 Be methodology combined with an environment conducive towards developing 10 Be-based records of ice-margin change has resulted in ice-margin reconstructions that identify a potentially fundamental negative feedback mechanism inherent to melting ice sheets in the Baffin Bay region – elevated and episodic meltwater delivery into the Labrador Sea results in a decrease in the Atlantic meridional overturning circulation and regional cooling, which, in turn, drives a brief reversal of deglaciation. Under the right conditions 10 Be can be used to develop centennial-scale, climatically relevant records of glacier and ice-sheet change. Highlights: Decades of 14 C ages and 10 Be ages are used to constrain the timing of early Holocene glaciation in the Baffin Bay region. Moraine deposition across Baffin Island and western Greenland occurred repeatedly and synchronously through the early Holocene. Moraine deposition is linked to pulses of Hudson Strait sourced freshwater and is similar in timing to canonical Bond events.