Reply to Carlson (2020) comment on “Deglaciation of the Greenland and Laurentide ice sheets interrupted by glacier advance during abrupt coolings”

Abstract

This Review quantitatively and qualitatively describes 10 representative Baffin Island fjords chosen to explore the nature of a glaciation in delivering sediment to a fjord, with focus on deglacial (within 13–6.7 kyr BP) and postglacial conditions (within 8.2–0 kyr BP). Fjords are compared using observed sediment thicknesses (49–175 m, averaged) and volumes (0.7–14.6 km3), and modeled sediment yields: (1) deglacial 140–1060 t/m2/yr; (2) paraglacial 45–350 t/m2/yr; (3) neoglacial 30–150 t/m2/yr; (4) Little Ice Age 70–440 t/m2/yr; and (5) Anthropocene 60–290 t/m2/yr. Modeled sediment loads, when converted to deposit volumes, compare favorably to observations from geophysical surveys and terrestrial mapping, or separately to sediment accumulation rates (SAR) determined from marine sediment cores. Fjord-averaged SAR during deglaciation range from 4.6 to 25 mm/yr, and 0.6–3.1 mm/yr for the postglacial interval. Fjords directly impacted by the Laurentide Ice Sheet (central and northern Baffin Island) are 2–3 times larger in dimensions than southern Baffin Island fjords, with ∼4.5x deglacial and ∼5x postglacial larger deposits, including well-defined ice-proximal outwash deposits. To the south, Penny Ice Cap associated fjords with no withholding sills, lose 30–40% of their incoming fjord sediment to Broughton Trough that dissects the continental shelf. Sunneshine is the only sampled fjord that was neither directly nor indirectly impacted by the Wisconsin continental ice sheet; Sunneshine responded instead to local maritime conditions and an alpine glaciation.