Mallard Bay, Portlock Glacier

Mallard Bay, Portlock Glacier

by | Sep 30, 2019

Mallard Bay is a shallow embayment on the eastern shore of Kachemak Bay, 15 miles (24 km) east-northeast of Homer and 26 miles (41 km) northeast of Seldovia, Alaska. At low tides, the entire bay dries to expose a mudflat. The name is not published on navigation charts and presumably is locally named after the ubiquitous migratory dabbling duck that is widely distributed across the Northern and Southern Hemispheres.

The Mallard Bay Trail is a 1 mile (1.6 km) hike with an elevation gain of 250 feet (75 m) that crosses a low ridge between Mallard Bay and Portlock Glacier Valley. The trail offers views and an open approach to Portlock Glacier and the Kenai National Wildlife Refuge. The Portlock Glacier once drained into Mallard Bay, but glacial retreat and thinning exposed the low ridge to effectively isolating the glacial runoff to the Portlock River and the Martin River. Continued glacial thinning has now isolated the runoff to only the Portlock River and the Martin River now mostly drains the Dixon Glacier. Portlock Glacier is named after Captain Nathaniel Portlock of the Royal Navy who was on Captain Cook’s third voyage in 1776. In 1785, Portlock and a group of investors, including George Dixon who also served with Cook, formed a partnership called the King George’s Sound Company to further commercialize the fur trade.

The southern Kenai Mountains are dominated by two icefields, which are drained by 38 distinct outlet glaciers, including seven that reach tidewater in fjords on the Pacific Coast. The recent retreat of outlet glaciers from the Kenai Icefields has exposed a vast array of moraine deposits on the eastern and western slopes of the Kenai Mountains that record multiple glacier advances into coastal forests during the late Holocene time. Tree ring dating together with radiocarbon and lichenometric analyses allows for the chronological reconstruction of these advances. These data indicate that three major intervals of Holocene glacier expansion occurred about 3600 yr B.P., 600 A.D., and during the Little Ice Age, from 1300 to 1850 A.D. The Little Ice Age glacial expansion involved tidewater glaciers that started advancing several centuries prior to their land-terminating glaciers and started retreating later. Land-terminating glaciers on the western mountain flank such as the Portlock and Dixon Glaciers retreated from their Little Ice Age maxima as much as two centuries before those on the eastern mountain flank. This may be explained by the order of magnitude differences in precipitation between the eastern and western slopes of the Kenai Mountains. The eastern tidewater glaciers receive about 10 to 33 feet (3-10 m) of annual precipitation compared to the western land terminating glaciers that receive 3-10 feet (1-3 m) of precipitation per year. Read more here and here. Explore more of Mallard Bay here:

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This ‘warming stripe’ graphic is a visual representation of the change in global temperature from 1850 (top) to 2021 (bottom). Each stripe represents the average global temperature for one year. The average temperature from 1971-2000 is set as the boundary between blue and red. The color scale goes from -0.7°C to +0.7°C. The data are from the UK Met Office HadCRUT4.6 dataset. 

Credit: Professor Ed Hawkins (University of Reading). Click here for more information about the #warmingstripes.

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