Accelerating glacier volume loss on Juneau Icefield driven by hypsometry and melt-accelerating feedbacks.

Globally, glaciers and icefields contribute significantly to sea level rise. Here we show that ice loss from Juneau Icefield, a plateau icefield in Alaska, accelerated after 2005 AD. Rates of area shrinkage were 5 times faster from 2015–2019 than from 1979–1990. Glacier volume loss remained fairly consistent (0.65–1.01 km³ a⁻¹) from 1770–1979 AD, rising to 3.08–3.72 km³ a⁻¹ from 1979–2010, and then doubling after 2010 AD, reaching 5.91 ± 0.80 km³ a⁻¹ (2010–2020). Thinning has become pervasive across the icefield plateau since 2005, accompanied by glacier recession and fragmentation. Rising equilibrium line altitudes and increasing ablation across the plateau has driven a series of hypsometrically controlled melt-accelerating feedbacks and resulted in the observed acceleration in mass loss. As glacier thinning on the plateau continues, a mass balance-elevation feedback is likely to inhibit future glacier regrowth, potentially pushing glaciers beyond a dynamic tipping point. The glaciers of Juneau Icefield, Alaska are reconstructed from 1770 to 2020 AD. Ice loss has accelerated dramatically, with a number of positive feedbacks now happening that accelerate ice loss and inhibit future stabilisation and regrowth. [ABSTRACT FROM AUTHOR]