In 30 years of exploring Alaska, I’ve encountered few scenes as surreal as what I saw when I flew out to Strandline Lake in early September, 2017. Hundreds of icebergs, some office-building-sized, lay littered across miles of empty lakebed.
One of the Continent's Largest Remaining Ice-Dammed Lakes
Strandline Lake is one of the largest ice-dammed lakes (called “jokulhlaups”) in North America. It lies about 70 miles West of Anchorage, just above Beluga Lake. Little-explored rivers draining the foothills of the Tordrillo Mountains flow into its upper end. At the bottom, the lake moats up against a lobe of the massive Triumvirate Glacier.
The steep-walled valley fills so deep that the pressure ultimately breaks a seal on a subglacial spillway, letting loose up to 25 billion cubic feet of water. This avalanche of water and shattered ice plows for miles under the glacier, then rooster tails out of an ice tunnel at the foot of the glacier, onrushes through a narrow, mile-long rock canyon, and spills out onto the outwash plains at the head of Beluga Lake.
The forces are so great you can see truck-sized blocks of ice heaved high on hillsides miles below the lake. The volume of water can cause the much larger Beluga Lake to rise by more than 30 feet in 40 hours. When was studied in 1982, researchers found that 95% of Strandline Lake itself drained when the ice dam burst, dropping its water level by 300 feet.
The lake used to empty every 2-5 years. Sportsman’s Air operates a camp on Beluga Lake and now tells me it’s emptied every year since 2011. One of their pilots, Austin Johnson, flew some guests over in the most recent event and said they were awe-struck.