Global Choke Points May Link Sea Level and Human Settlement at the Last Glacial Maximum

Abstract

Global choke points are preeminent nodes in geographic networks and geopolitical touchpoints subject to control by nations. They appear today as recurring theaters of conflict worldwide and also in archaeological investigations delving thousands of years back in time. How different were today's global choke points at the Last Glacial Maximum (LGM) ~20,000 years ago? For the first time, we map nine of them to visualize their conditions at LGM. The global feature aquaterra-all lands inundated and exposed repeatedly during the Late Pleistocene ice ages-initially was mapped as first approximations of sea level. Here we refine its boundaries using Glacial Isostatic Adjustment (GIA) models to account for the Earth's deformation and horizontal migrations of shorelines in response to glacial melting. We found three choke points sufficiently open to navigation, but six others presented substantially greater barriers than today. Implications include strategic insights on where to search for submerged evidence of human settlement.

The Bering Transitory Archipelago: stepping stones for the first Americans

“…Retrospective sea-level modeling affirmed a third, stunning alternative when Dobson et al [2020] documented scores of islands that could have served as stepping stones for maritime travelers. This archipelago would have been an ideal staging area for LGM travelers heading east.…”

“…The archipelago's eastern shift after 10,000 BP would have favored migrating to North America by the seaward route. We urge underwater archaeologists to search for landfall settlements at depths of −90 m to present sea level off the coast of Alaska [Dobson et al, 2020].…”

“…Subsequently, the Kelp Highway hypothesis posited a maritime route sustained by coastal resources and nearshore kelp forests [Erlandson et al, 2007]. Then, Dobson et al [2020] retrospectively mapped an ancient transitory archipelago that offers a third alternative: an island-rich maritime route like stepping stones across the Bering Sea. Scores of scattered, continuously evolving islands were available to maritime people at least as early as 30,000 BP to as late as 8000 BP.…”

“…Second, Spada and Galassi [2017] refined the boundaries of aquaterra at coarse resolution for the whole earth and finer resolution for Doggerland and Beringia, using a Glacial Isostatic Adjustment (GIA) model. Third, Dobson et al [2020] conducted GIA mapping and hypsometric analyses of nine global choke points-Bering Strait, Isthmus of Panama, Bosporus and Dardanelles, Strait of Gibraltar, Straits of Sicily and Messina, Isthmus of Suez, Bab al Mandab, Strait of Hormuz, and Strait of Malacca-to assess their status at the Last Glacial Maximum (LGM) ∼20,000 years ago. In the course of that global research, our paleotopographic reconstructions digitally discovered previously unnamed islands in a broad swath across the Bering Sea.…”

Post-LGM coastline evolution of the NW Sicilian Channel: Comparing high-resolution geophysical data with Glacial Isostatic Adjustment modeling

“…To deal with "gravitationally self-consistent" time-variations of the Earth's topography in response to GIA [7], we follow Milne and Mitrovica [41] and we employ a generalized formulation of the SLE, which accounts for the horizontal migration of shorelines, for the transition between grounded and floating ice during deglaciation, and for the effects of Earth rotation on sea-level change. Our numerical implementation of the generalized SLE has been successfully tested against other independently developed SLE solvers [42] and it has been recently used to study the dynamic evolution of the global coastlines since the LGM [43,44].…”