Heightened North Pacific Storminess during Synchronous Late Holocene Erosion of Northwest Alaska Beach Ridges

Abstract

AbstractA progradational regime of falling sea level and/or high sediment input has produced extensive beach ridge plains in northwest Alaska during the last 4000 yr. Eleven Chukchi Sea beach ridge complexes, oriented at various angles to wind fetch, provide a cumulative history of longshore transport and erosion. Archaeological and geological upper limiting radiocarbon ages (n = 59) allow correlations between depositional units on seven beach ridge complexes. Progradation started 4000 yr B.P. at nearly all complexes, as eustatic sea level stabilized. Two disconformities or truncations are found on most of the complexes, providing time-parallel storm horizons, dated at 3300-1700 and 1200-900 14C yr B.P. Between 1700 and 1200 14C yr B.P. most of the complexes prograded, indicating the predominance of less-stormy conditions. Modern synoptic patterns that produce Chukchi beach ridge erosion are linked to northerly shifts in North Pacific storm tracks. The regionwide beach ridge erosional truncations correlate with records of glacier expansion, heightened precipitation evident in tree-rings, stream flooding, and shelf deposits reworked by storm surges.