Laboratory experiments on the paleo-jamming of the Bering Strait

On the basis of scour marks and ice-rafted debris found on the Northwind Ridge, northwestern Alaskan coast and Chukchi Shelf (and Cap and Borderland), and on the basis of the earlier ideas presented by De Boer and Nof (2004, DN hereafter), it has been hypothesized that icebergs created a temporary dam at the mouth of the Bering Strait (BST). This article describes an examination of this concept in the laboratory.At the beginning of the Holocene, approximately 11,000 years before present (11 kyr BP), both oceanic and atmospheric paleo-temperatures increased abruptly. DN suggested that, with an open BST and no-convection in the North Atlantic, the global wind field would force water to flow from the Arctic to the Pacific (contrary to modern day configuration). We propose here and in a companion paper that the opening of the BST and the initiation of this negative flow are responsible for the abrupt increase in temperature. Further, we propose that the abruptness with which this event occurred, was due to the breakup of a temporary iceberg dam at the mouth of the BST 11 kyr BP. (The dam was already 15 m above the BST sill at that time.) This breakup allowed the freshwater anomalies, capping the convection area in the North Atlantic, to be flushed (out of the Atlantic) through the Arctic and BS into the North Pacific.Using a simple laboratory box model, this temporary damming and release of icebergs is recreated. Results show the stability of the dam to be dependent on the rate of sea-level rise, which at 1 cm/yr should be sufficiently slow to allow a temporary dam to exist for thousands of years. Sea ice probably fused icebergs together, and through ridging could have created a 15 m ice wall, which broke up 11 kyr BP. On breaking (of the ice wall), approximately 3.5 Sv of water would have flushed into the North Pacific, implying a flood lasting for approximately 3 years. This was followed by a reduced flow of 2.2 Sv lasting 440 years or less (until the low salinity water which prevented convection in the Atlantic during the Younger Dryas was flushed out and the convection re-started).