As Most Glaciers Retreated, Taku Glacier (AK) Was The Exception; Now It, Too, Has Begun To Shrink
Along the rugged Southeast Alaska coast, 30 kilometers northeast of the state capital Juneau, a tidewater glacier has largely defied global trends by steadily advancing for most of the past century while most glaciers on Earth retreated. This 55-kilometer-long and nearly 1,500-meter-thick tidewater glacier, named Taku Glacier, or T'aaḵú Ḵwáan Sít'i in the language of the Indigenous Tlingit people, has been the focus of continuous scientific study for more than 70 years. Some records even extend back to the mid-18th century. With this long observation record and the glacier’s year-round accessibility and proximity to Juneau and adjacent research facilities, Taku provides an unparalleled locale to study tidewater glaciers and their response to Earth’s rapidly changing climate.
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From 1890 until 2015, a time when most glaciers worldwide retreated, Taku Glacier advanced. The glacier’s sustained advance, especially under a warming climate, has captivated researchers for more than 70 years. The resulting records of mass balance, ice flow, ice thickness, and sediment processes make Taku Glacier’s advance perhaps the best documented of any tidewater glacier in the world.
Taku Glacier calved icebergs into Taku Inlet through the early 20th century, but by 1950 calving had largely ceased as its sediment moraine rose above the water surface, protecting it from the ocean’s influence. As the glacier continued to advance during the next 7 decades, it pushed this moraine into Taku Inlet. Today the moraine extends 12 kilometers downstream from the glacier’s terminus, largely filling Taku Inlet. Despite its reach, the moraine rises only a few meters above sea level at its highest point, and high tides and storm surges infiltrate Taku Inlet to within a few tens of meters of the present-day terminus.
Taku Glacier’s advance significantly slowed in the late 1980s and has now transitioned to retreat and mass loss [McNeil et al., 2020]. Regional temperatures rose approximately 2ºC in the past 70 years, increasingly influencing the glacier’s mass. The glacier gained mass and advanced between 1946 and 1989, but the mass change approached equilibrium, and the advance slowed by 72% after 1989. Since 2013, the glacier has lost mass, thinning at an average rate of 1.3 meters per year, and it has retreated from its moraine (Figure 3), with record annual mass loss in 2019. The past few decades of observations imply that climate warming has caught up with Taku Glacier, likely initiating the retreat phase of the tidewater glacier cycle.
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https://eos.org/science-updates/the-imminent-calving-retreat-of-taku-glacier
