A Terraced Terrain Indicates Sea Level Change


‘Let’s start by observing the modern environment,’ Alan Mix, co-chief scientist, says while looking out over a series of terraces, cut down the middle by a braided river.  We hike from the helicopter drop off to the modern delta where sea ice and icebergs have washed up and sit perched on the shoreline.  Our goal is to investigate how relative sea level has changed in Northwest Greenland since the deglaciation of the last ice age.


Relative sea level reflects both global changes in sea level, which rose as the large ice sheets melted, and local processes, which caused relative sea level to fall in Northwest Greenland due to isostatic rebound of the crust following the last glacial.  Understanding isostatic adjustment over the last ten thousand years provides an important constraint on the size and variability of the past Greenland ice sheet, complementing datasets by other expedition science teams, providing a clearer picture of the Petermann Glacier system, and constraining regional isostatic adjustment models.


Our team, Alan Mix, Jorie Clark, Anna Glueder, Chris Holm, and I, using helicopters from the Oden, have visited two paleo-sea level sites near Petermann Fjord, identified from satellite imagery and previous studies, and we have plans to visit a few more around Nares Strait.  After observing the modern depositional environment, we hike from the modern shoreline inland along the river cut.  Along the way we search for datable material like mollusk shells and measure elevation to pair constraints on the age of the paleo-shoreline with the amount of relative sea level change.


The landscapes are spectacular.  There is very little vegetation and the perfectly flat terraces, which were deposited in shallow marine, beach, and delta environments, can feel alien.  We are in awe of the rare animal tracks and small rugged wildflowers we encounter.  It will be exciting to see what stories these places reveal during our post-cruise analysis of the samples collected.


Written by: Brendan Reilly

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