False Pass, Alaska: Significant changes in depth and shoreline in the historic time period

Abstract

Global ocean circulation is limited partly by the small passes of Alaska's Aleutian Islands, which restrict North Pacific Ocean water from flowing north into the Bering Sea and eventually to the Arctic, but the size and shape of these Aleutian passes are poorly described. While quantitatively redefining all of the Aleutian passes, we determined that the easternmost pass, with the cryptic name of False Pass, and with an unusual configuration of having both northern and southern inlets, had two or more inlets to the Bering Sea in the recent past, but that it has only a single northern inlet now (15,822 m 2 ), roughly equivalent in size to the southern inlet, Isanotski Strait (15,969 m 2 ). Navigational charts depict the opposite: two inlets to the Bering Sea now, but just one in older charts . This discrepancy inspired a thorough review of the hydrographic history from which we concluded that the second northern inlet did exist and hypothesize that it was a remnant of multiple former openings, or a single large opening, potentially allowing greater northward flow of warmer, fresher Alaska Coastal Current water. While the shoreline changes that we document here are often regarded as minor, ephemeral events, we document similar, nearby, permanent shoreline shifts which changed Ikatan Island into a peninsula and which shifted the Swanson Lagoon outlet over 3 km to the east.

Passes of the Aleutian Islands: First detailed description

“…Hunt and Stabeno (2005) summarize several significant ecological impacts of this western/eastern division in water masses at Samalga Pass, including differences in primary production; zooplankton species composition; species diversity of cold‐water corals; groundfish species richness, abundance, diet composition, and growth rates; seabird foraging guilds; Steller sea lion diets ( Eumetopias jubatus ); and cetacean distributions. The location of this division of water masses at Samalga Pass makes bathymetric sense because the minimum opening of Shelikof Strait (6.504 km 2 : Zimmermann et al., 2019) is approximately equal to the sum of the eastern Aleutians passes through Samalga (6.189 km 2 , including the 15,800 m 2 estimate of False Pass from Zimmermann & Prescott, In Review). Samalga is by far the largest and deepest of these eastern passes, accounting for 61% of the group's cross‐sectional area, and thus, its size may dictate the importance of its location.…”

“…The cartographic information for the easternmost pass—False Pass—was so confusing and contradictory that we analyzed it in a separate project (Zimmermann & Prescott, in review). False Pass is unusual as it is the only Aleutian Pass that directly connects the shelves of the western Gulf of Alaska and eastern Bering Sea, it has constricted northern and southern openings with two extensive capes blocking most of the northern opening, and some information indicated that there might be an additional inlet through one of those capes (Figure 1).…”

Gateway to the arctic: Defining the eastern channel of the Bering Strait

“…Comparison between the base-10 log of maximum depth (found on the path of minimal cross-sectional area) of passes/inlets and the base-10 log of their minimal cross-sectional areas for Alaskan passes (as per legend). The linear regression was run through only the Aleutian Passes (Zimmermann and Prescott, 2021a), False Pass (both the northern False Pass inlet and southern Isanotski Strait;Zimmermann and Prescott, 2021b), and Shelikof Strait (Zimmermann et al, 2019) points. Bering Strait eastern channel data are included in the plot to show that their cross-sectional areas (overall minimum and minimum through the moorings) exceed the 95% confidence intervals and are, therefore, more uniformly deeper than expected for their maximum depths.…”

“…While most researchers have already noted that the strait is small, we wondered if it was unusually shallow for its cross-sectional area or unusually narrow for its depth. There are limited data available to test this question, so we plotted the maximum depth versus cross-sectional area for other recently analyzed inlets in Alaska, such as the passes of the Aleutian Islands (Zimmermann and Prescott, 2021a), False Pass (Zimmermann and Prescott, 2021b), and Shelikof Strait (Zimmermann et al, 2019b) as a reference (Figure 4).…”

Global Distribution and Morphodynamic Patterns of Paired Spits Developed at the Mouths of Interdistributary Bays of Deltas and within Coastal Channels

“…Usually, paired spits have been described at the mouth of bays and rivers [39]. However, the development of paired spits constraining the mouths of interdistributary bays of deltas has only been described for the Po River delta (N Adriatic Sea) [40][41][42][43][44], and the development of paired spits within channels have only been very briefly reported [45][46][47]. Therefore, determining the global distribution, geomorphological characteristics and morphodynamic evolution of paired spits located both at the interdistributary bays of deltas and within coastal channels was the main objective of this study.…”