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Herschel Island 2014: The land that is disappearing
(Photo: Jaroš Obu) Quickly eroding coast at Stokes PointMonday, 1st of September 2014
Herschel Island was formed as an ice thrust moraine. This means that the glacier excavated the sea floor and deposited it together with the ice. For this reason the ground is characterised by an abundant massive ground ice and soft sediment. And the mainland coasts have similar composition as well.
When this ice and sediment are exposed to sea waves, they erode very quickly. Either very steep bluffs or retrogressive thaw slumps can form. The retreat of coasts and slump headwalls is one of the topics that are in the main interest of our group.
Anna and Gavin are interested in the rates of Yukon Coast retreat and the factors that cause the difference of erosion.
(Photo: Jaroš Obu) Anna and Gavin during DGPS survey Jaroš is studying the elevation changes in the coastal transect by comparing two LIDAR digital elevation models.
When the helicopter arrived, we spent four days surveying the study sites between Komakuk and King Point with DGPS and measuring the shear strength of the ground.
Measurements showed that coastline is retreating for several meters per year on the most exposed places.
Calculations based on LIDAR DEMs showed that on an exposed part of the coast on the northern part of the island, the 15000 m3 (which equals to approx. 600 trucks of material) material was moved on 2500 m2 area (one third of football field) during one year.
Beside the important material loads that are released into sea, the coastal erosion endangers the buildings that are placed along the coasts.
Although we didn't do any flume measurements at slump D this year, we did other planned surveys. Anna, Jaroš and Gavin measured the exact headwall positions at slumps A, B, C and D with the DGPS to compare them with positions from previous years in order to estimate progression inland.
The second activity on slump D was taking active layer samples for George's PhD research.
(Photo: Jaroš Obu) Slump D from the helicopterHe wants to find out how much organic carbon that has been activated by slump disturbances has been released as carbon dioxide and methane and how much of it has been redeposited.
Now when the rainy and grey days are over, we all enjoy the sun rays, colourful sunsets and the full moon which started illuminating the evening dusk, which came with the end of the polar day.
But the most of excitement brought the helicopter since everyone had a chance to fly and see the island from the air.
On the day that the helicopter left, we finished most of our scientific activities. This means that our stay on the Herschel Island is slowly coming to an end and we are all now slowly starting to pack our samples and equipment.
Written by Jaroš