Observational dataset from Drew Point, Alaska used in the calibration of the Arctic Coastal Erosion (ACE) Model

This repository contains three interrelated datasets from Drew Point Alaska. The first is a geochemical and mechanical characterization of permafrost cores collected in 2018. The second contains permafrost temperatures as a function of elevation between July 1 and September 8, 2018. The third is a reporting of erosion from a single polygon located at 70⁰ 52’ 50.0196” N, 153⁰ 53’ 25.4418” W between July 1 and September 30, 2018. 

Permafrost cores (4.5-7.5 m long) were collected April 10th-19th, 2018, along a geomorphic gradient near Drew Point, Alaska to characterize permafrost geochemistry, material, and mechanical properties. Cores were collected from a young drained lake basin, an ancient drained lake basin, and primary material that has not been reworked by thaw lake cycles. Measurements were conducted to establish salinity, organic carbon content, water mass for effective porosity, and soil/sediment masses, grain sizes, and bulk densities in ice-bonded sediments as a function of bluff elevation.  Experimentation on a small subset of these natural cores was also used to establish three mechanical material properties: elastic modulus, compressive yield strength, and tensile yield strength. Mechanical stress strain properties as a function of ice saturation and porosity were obtained through direct tensile, Brazilian tensile strength, and unconfined compressive strength testing. Distinct compositions of ice saturation and porosity were achieved by controlling the testing chamber temperature and selecting distinct sections of the core respectively.

The D405 BeadedStream satellite telemetered datalogger with a 5.5 m long standard digital temperature cable recorded temperature values every day from Apr. 22 to Jul. 20 and then hourly from Jul. 20 through the block failure event on Sept. 1, 2018.  The thermistor string had 10 sensors measuring temperature changes at the following bluff elevations: -0.3, 0.0, 0.2, 0.5, 0.7, 1.7, 2.7, 3.7, 4.2, and 4.7 m.  Niche measurements are inferred from vertically resolved temperature changes, as measured hourly by a thermistor string placed within the void left by the 7.5 m long core. This is the first dataset, to our knowledge, that captures hourly-resolved niche formation and ensuing block collapse offering an unparalleled calibration opportunity for models capable of temporally evolving niche dynamics (like the ACE model).  Additionally, environmental conditions were measured by a permanent USGS weather station. Observational measurements of air and subsurface temperatures from 5 cm to 120 cm depth at 5 cm increments were collected hourly.  Both of these datasets between Jul. 1 through Sept. 8, 2018 are documented here.

Bluff face erosion measurements were collected through four repeat aerial unpersoned vehicle (AUV) surveys as well as from daily-resolved time-lapse calibrated images. These measurements are most representative of the changes experienced at the top of the bluff.  A quad-rotor phantom AUV acquired repeat images along a 1.5 km stretch of coastline on Jul. 25, Jul. 30, Aug. 04, and after block collapse on Sept. 30 2018 (note, all dates and times are presented in Greenwich Mean Time (GMT)).  Twelve transect lines intersect with the calibration polygon and erosion amounts between the surveyed dates are presented for each transect.  A time-lapse camera (Buckeye cam x80 model) was configured to take hourly photos and documents the polygon with the vertical thermistor breaking along an ice wedge between Aug. 31 and Sept. 1 2018.  Photographs from this camera were analyzed using reference distances to create a daily record of bluff top erosion.  Daily amounts of thermo-denudation between Jul. 1 and Aug. 31 from this analysis is presented in this dataset.