INCREASING COASTAL SLUMP ACTIVITY IMPACTS THE RELEASE OF SEDIMENT AND ORGANIC CARBON INTO
THE ARCTIC OCEAN
Justine Ramage
Anna Irrgang, Anne Morgenstern, Hugues Lantuit
Introduction
Sea Ice median September Extent (1979 - 2000) CAFF Arctic definition
AMAP Arctic definition Permafrost Coastlines Continuous Permafrost Discontinuous Permafrost Sporadic Permafrost Isolated Patches
4 5 6 7 8 9 10
3 2
1 Barents Sea Kara Sea Laptev Sea East Siberian Sea Chukchi Sea Beaufort Sea Hudson Bay Lincoln Sea
Norwegian Sea Wandel Sea
Slump along the Yukon Coastal Plain, 2015
Introduction
Slump along the Yukon Coastal Plain, 2015
Introduction
Lantuit, H., & Pollard, W. H. (2005). Temporal stereophotogrammetric analysis of retrogressive thaw slumps on Herschel Island, Yukon Territory. Natural Hazards and Earth System Science, 5 (3), 413-423.
Introduction
372 www.gsapubs.org
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Volume 45|
Number 4|
GEOLOGY(Ham and Attig, 1996), and modified glacigenic permafrost landscapes in western Arctic Canada during the early Holocene warm period (Murton, 2001). The recent acceleration of thaw slump- ing (Segal et al., 2016a) and the development of immense mass-wasting complexes in northwest- ern Canada demonstrate the efficiency of this climate-sensitive process in mobilizing glacial sediment stores (Fig. 1; Fig. DR1).
To explore the relation between glaciated landscapes and permafrost terrain sensitivity we mapped thaw slumps at regional to continen- tal scales and investigated the nature of fluvial effects. We integrated spatial data on thaw slump distribution and patterns of fluvial sedimentary disturbance with theory on the preservation of relict Pleistocene ground ice (e.g., Murton et al., 2005) and paraglacial landscape change (Ballan- tyne, 2002) to demonstrate that (1) permafrost has delayed the geomorphic evolution of glaci- ated terrain, so that these landscapes retain sig- nificant potential for climate-driven change; and (2) the patterns and intensity of accelerated thaw slump activity in northwestern Canada and the nature of fluvial effects indicate deglaciation- phase or early postglacial geomorphic dynamics.
METHODS
To investigate the distribution of slump- affected terrain, a 1,274,625 km2 area of north- western Canada was mapped using SPOT (Sat- ellite Pour l’Observation de la Terre) 4 and SPOT 5 satellite imagery (A.D. 2005–2010), hosted on the Government of the Northwest Ter- ritories (GNWT) Spatial Data Warehouse web viewer (http://www.geomatics.gov.nt.ca /sdw.
aspx), to classify 15 × 15 km grid cells accord- ing to the density of large active slumps (>1 ha).
The grid classes included none (0 slumps), low (<5 active slumps), and medium (6–14 active slumps) to high (≥15 active slumps). The data, consisting of 5665 ranked grid cells, were com- piled in ArcGIS 10.0–10.2 (https://www.arcgis .com/; for methods and data, see Segal et al.,
2016b).
The association between slump-affected ter- rain and the late Wisconsinan ice sheet margin (Dyke and Prest, 1987) was assessed using the GLM (generalized linear model) function in
“R” (R Core Team, 2013) to perform a logistic regression (family = binomial; link = logit) that modeled the odds (p/q) of disturbance in each grid cell as a function of the Euclidian distance (d) from the ice margin, p/q = ead + b. To examine if broad-scale patterns of thaw slump distribu- tion are supported by fine-scale data sets, we used a digitized slump inventory from the Peel Plateau, northwestern Canada, derived from color satellite imagery (2007–2008; Segal et al., 2016a). Slump-affected terrain in the Peel Plateau was plotted along a 100 km geological transition from unglaciated terrain to moraine to Holocene alluvium.
To investigate the association between thaw slumping and glaciated terrain at the circumpo- lar scale we mapped the records of relict ground ice and thaw slump occurrences from the pub- lished literature. Metadata, ice type, and refer- ences are provided in the Data Repository, in addition to the sources of spatial base-layers (Figs. 2A and 2B).
To describe the nature of topographic and sedimentary disturbance resulting from thaw slumping, and to derive order of magnitude esti- mates of denudation rates, we used a surface model derived from 2011 lidar data from the GNWT. The material volumes displaced by indi- vidual thaw slumps were estimated by recon- structing pre-slump topography using contour lines, and then differencing the regridded old topography from the new.
Fine-scale slump mapping in the Peel Plateau and a database of total suspended
sediment concentrations (TSS) in streams (n
= 198) of the Peel River watershed (80,000 km2) were used to assess slump-driven flu- vial effects. Catchment sizes were estimated using a topographic model derived from the Canadian Digital Elevation Model (20 m reso- lution) (Government of Canada, 2000). Tau- DEM (v.5.3) Fill, D8, and Flow Accumulation algorithms (http://hydrology .usu .edu /taudem/;
Tarboton, 1997) were applied to trace the drain- age network and catchment area upstream of thaw slump and water sampling locations. To investigate the influence of slumping on the flu- vial sedimentary regime, TSS concentrations during the summer flow period for streams in the Peel basin were compiled (Kokelj et al., 2013; Chin et al., 2016) and plotted against catchment area. Samples from larger tributar- ies collected from 2000 to 2005 were provided by the GNWT.
D
A
B
Proportion ofTerrain with Slumps (%)
Distance from Ice Margin (km)
0.0 0.1 0.2 0.3
0.4 0 200 400 600 800
C
1200 800 400
0 20 40 60 80 0
0.0 0.1 0.2
TerrainArea affected by Elevation (m)Ice Extent
Peel Plateau Mackenzie Delta
Transect distance (km) Unglaciated
Slumping (km/100 km)22
D
Alluvium Hummocky Moraine
Richardson Mnts
100
Figure 2. Thaw slump distribution and glaciated terrain. A: Slump-affected terrain in northwest- ern Canada and positions of the Laurentide Ice Sheet from ca. 18–11 ka. B: Circumpolar map showing published observations of thaw slumps and thick ground ice in glaciated permafrost terrain. C: The proportion of terrain with slumps and distance from the late Wisconsinan ice front (thick blue line in Fig. 2A). A χ2 test comparing the logistic model to a null model (inter- cept only) is highly significant (χ2 = 475.5, P < 0.01). D: Topography and slump-affected area along a west to east corridor (black rectangle in A) through unglaciated terrain, hummocky moraine, and Holocene alluvium.
Kokelj, S. V., Lantz, T. C., Tunnicliffe, J., Segal, R., & Lacelle, D. (2017). Climate-driven thaw of permafrost preserved glacial landscapes, northwestern Canada. Geology, 45 (4), 371-374.
Introduction
Ramage et al., 2017
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138°W 138°W
139°W 139°W
140°W 140°W
69°40'N 69°40'N
69°20'N 69°20'N
69°N 69°N
0 15 30
Kilometers
RTSs size [ha]
!
( 0.00 - 3.00
!
( 3.00 - 6.13
!
( 6.13 - 9.25
!
( 9.25 - 20.81
Erosion rates [m / yr, 1970-2011]
0.0 to 0.6 - 0.7 to 0.0 -1.0 to -0.7 -4.4 to -1.0
Glaciation limit
±
Be au
f or t Se
a B e a u f o r t S e a
Herschel Island
Objectives
The objectives are:
ü to measure their evolution on a ca. 150 km coastline along the Yukon Coast between 1951 and 2011
ü to estimate the amount of carbon released from the land to the shore
?
Part 1: evolution
2. Landform digitalization and classification
1. Georeferencing aerial photos (1950s and 1970s)
±
Shoreline 1952 Active RTSs 1952
Active RTSs 1972 Stable RTSs 1972
Active RTSs 2011 Stable RTSs 2011
0 25 50 100
Meters
1952
1972
2011 A
B
C
D 3. Extraction of geospatial
data
A. Landform identification
Stabilized surface
Active surface
Slumps reactivating on previously disturbed surfaces
Part 1: evolution
Part 1: evolution
Evolution of slumps 1952-2011
0 50 100 150 200
1952 1972 2011
Year
Number of RTSs | Coverage (ha)
Legend
L− active RTSs L− stable RTSs Mm− active RTSs Mm− stable RTSs Mr− active RTSs Mr− stable RTSs
LMm Mr
Number RTSs Coverage RTSs
L - Lacustrine plains Mm - Rolling moraines Mr - Ice-thrust moraines
2011
1972 1972 2011
Volume of material eroded due to slumping between 1972 and 2011 ((S1 -S2)*L)) Retrogressive thaw slump in 2011
Volume of material eroded and transported alongshore due to coastal erosion between 1972 and 2011 (R * dH)
HEADWALL HEADWALL
SHORELINE SHORELINE
Volume of material reworked and settled in the retrogressive thaw slump between 1972 and 2011 (estimated to be 5.5 %) coastal retreat (R)
length of the slump in 2011 (L)
height of the slump (H)
mean elevation before slumping in 1972 (S1)
mean elevation after slumping in 2011 (S2)
a b c d
Part 2: fluxes
B. Volume estimations
Part 2: fluxes
B. Volume estimations
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±
0 100200 400 600Metersactive RTS stable RTS
! Elevation points
LiDAR elevation 100 m
0 m
SPLINE elevation 62 m
0 m
10 Mr 9
11 Mr 2
12 Mr 12
13 Mr 7
18 Mm
0 19
L 0
20 Mm
1 22
L 0
23 Mm
0 24
L 1
28 Mr 12
29 Mm
0 32
L 1
33 Mm
0 34
L 1
35 L 1
36 Mm
2 0
20000 40000 60000 80000 100000 120000
volume of eroded material(103 m3 )
WEST EAST
Segment order Geologic unit Number of RTSs
