Cape Espenberg

Cape Espenberg is a cape located on the Seward Peninsula in Alaska, on the Chukchi Sea coast.

Cape Espenberg points northwards, 42 mi NW of Deering, Kotzebue-Kobuk Low. On its southeastern side there is the small Goodhope Bay, an inlet of the Kotzebue Sound.

Named in 1816 by Lt. Otto von Kotzebue (1821, p. 236) for Dr. Karl Espenberg, a surgeon who accompanied Captain (later Admiral, IRN) Adam Johann von Krusenstern on his voyage around the world in 1803-06.

Cape Espenberg lies on the Arctic Circle at the terminus of a 30 km long mainland attached beach ridge plain at the northern limit of Seward Peninsula, in western Alaska. At the entry of the shallow Kotzebue Sound embayment, Cape Espenberg faces a potential open water fetch of 1000 km across the Chukchi Sea, an impact that is restricted by a perennial ice cover decreasing in duration the last 10 years.

Cape Espenberg, located 40 km east of a pronounced easterly deflection in the coast, is the depositional sink of a 200 km long littoral transport system fostered by a dominant west to northwest wind regime. Due to an abundant offshore source, sandy barrier islands front most of the northwest facing Seward Peninsula from Bering Strait into Kotzebue Sound, enclosing several extensive lagoons. The Chukchi Sea is microtidal < 50 cm, and the prevailing westerly currents maintain a series of widely spaced offshore bars that typically damp onshore wave energy. Storm surges occur with some regularity in the fall, with the extreme events, attaining a maximum elevation of 3 to 4 meter.

The beach is extremely planar and composed of comparatively well-sorted fine and medium sand, with a few stray cobbles of uncertain but probable ice-rafted origin. Dunes occur in the back beach, stabilized by grass, attaining a height of ca. 4 m. The sand is considered by geologists to reflect multiple sources. Its most common constituent, a fine quartose sand is most dense on the shallow shelf north of Bering Strait and reflects a complex history. A significant amount of Yukon River sand entered the southern Chukchi Sea during the Holocene transgression, hypothetically forming and reworking a series of early Holocene barriers into a retreat massif similar to that of the mid-Atlantic.

A secondary source of sand may be as a fluvial addition from south-trending paleo-Noatak and Kobuk rivers cross the exposed subcontinent of Beringia, and reworked into Pleistocene dunes during lower sea levels. The dark medium sand reflects updrift bluff erosion of a tephraeous maar eruption about 17,000 years ago. Sand supply is maintained by onshore transport during a five-month open water period from June to November. Although in the long-term, as established by geological 14C ages, over the last 4000 years, sand transport is onshore and progradational, in the short term, storms and transient current reversals lead to offshore transport and erosion of Espenberg beaches. Locally, beaches have witnessed significant width and depth reductions in the last five years; current reversals are also possibly more common.

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