Deep draft icebergs from the Barents Ice Sheet during MIS 6 are consistent with erosional evidence from the Lomonosov Ridge, central Arctic

Abstract

Iceberg scour marks on the Lomonosov Ridge in the central Arctic imply that bergs with drafts exceeding 850 m once existed in the Arctic, whereas similar erosion patterns observed on the Yermak Plateau suggest that some of these deep-keeled icebergs exited the Arctic through the Fram Strait into the Nordic Seas. An intermediate complexity climate model with a dynamic and thermodynamic iceberg model is used to simulate the collapse of the Barents Ice Sheet during MIS 6 with the purpose of investigating if deep-draft "mega"-icebergs can reach and ground on the Lomonosov Ridge. A number of simulations with different iceberg sizes show that deep-draft bergs seeded from near the Franz Victoria Trough could indeed have reached the Ridge, whereas other bergs crossed the Yermak Plateau and exited through the Fram Strait. The draft of the bergs mainly determines the trajectory, with only minor influence from the mass, and length and width of the bergs. This work is consistent with previous speculation that these icebergs originated from the disintegration of the Barents Ice Sheet during Marine Isotope Stage 6 (MIS 6; 140 ka BP), but suggests their origin was more likely to be from the western, rather than eastern, major ice stream of that ice sheet. The long-term impact on the overturning circulation from melting icebergs is more severe than that from a freshwater pulse of equivalent magnitude, and a correct representation of icebergs in paleoclimate models is therefore of importance. © 2010 by the American Geophysical Union.