ChangeDetectionofPermafrostThaw:ObservationsonBykovsky,LenaDelta
F. Günther*, G. Grosse, P. P. Overduin, A. A. Veremeeva & M. N. GrigorievCRYO-118 (* [email protected])
BACKGROUND
0
5
10
15
1951
1961
1971
1981
1991
2001
2011
JUN JUL AUG SEP
JUN JUL AUG SEP
Pos
. mea
n da
ily a
ir te
mp.
[°C
]
Time series of air temperature show lengthen-ing and warming of the arctic summer in Tiksi.The season available for permafrost thaw haslengthened by two weeks. Simultaneously, Tair
increased from 5.9 to 7.3 °C.
OBJECTIVES
How widespread is permafrost thaw, is itchanging, and what are the implications for fu-ture landscape development in the Arctic?
• quantification and change detection ofhistorical and modern thermokarst rates
• carbon mobilization through thaw-related terrain lowering (subsidence)
• hazard exposure to sea level rise
STUDY REGION
SamoylovStation
Sobo-SiseKurungnakh
BykovskyPeninsula
MuostakhIsland
Tumatskaya
Our focus in the Lena Delta region (East Siberia,Russia) is on areas with Yedoma prevalence,where we expect permafrost to be most sensi-tive to changing environmental conditions.
FIELD WORK
During two subsequent expeditions in 2014 and2015, topographic elevation data was collectedby terrestrial laser scanning and tied to fixedreference markers. ALT 2015: 39 ±11 cm
18
20
22
24
26
28
30
elev
atio
n [m
a.s
.l.]
<=30
31-35
36-40
41-45
46-50
51-55 >5
5
max. active layer thickness [cm]
R² = 0.82 y = -0.5x + 27.6 n = 213
Measuring active layer thickness and mappingof a thin protective layer revealed high thawvulnerability of yedoma uplands.
DATA FUSION & CHANGE DETECTION
RapidEye scene draped over fusioned and quasi-simultaneous WorldView-1 and WorldView-2DEM with previously unmatched detail at 0.5 mresolution. ICESat GLAS (Global Land SurfaceAltimetry) tracks build several profiles across thethermokarst-affected landscape.
• by creating robust photogrammetric im-age blocks of very high resolution multi-temporal satellite images (GeoEye, World-View, QuickBird etc.), aerotriangulation,orthorectification, and thus data fusion ismuch more efficient and accurate
• simultaneous handling of all imagerythrough common tie points ensures bestpossible coregistration
• to span a long period of time for changedetection, aerial imagery (1950s & 1980s) isused as basic datasets for 2D analyses
• Comparison of ICESat GLAS (release 34)data above ellipsoid with modern WV-DEM data captures elevation change dur-ing the warmest decade in the study region
PERMAFROST THAW-RELATED TERRAIN SUBSIDENCE
GRAPHIC© Yves Nowak, AWIpure ground ice
active layerfrozen soil and rock
permafrost thaw-related subsidence (terrain lowering)
thermo-abrasion
seasonal thaw of active layer encounters ice-rich horizons
undercutting by waves thermo-abrasion
thawingpermafrost iceon outrcop
old surface of ice-rich yedoma upland
coastal erosion
Schematic diagram of terrain subsidence close toa retreating permafrost coastline. Local drainagegradients provide favorable conditions for re-moval of melt water from ground ice thaw.
-0,3
-0,2
-0,1
0
0,1
thaw
sub
side
nce
rate
200
3/20
08 -
2015
[m
a-1
]
ICESat laser altimetry campaigns 2003 20082007200620052004
R2 = 0.75 y = 0.018x + 36.4 n = 385
Elevation differences between specific ICESatcampaigns (early winter) and a WorldViewDEM, representing the topography in August2015. Elevation change over time suggests in-creasing terrain lowering in the recent past.
CONCLUSIONS AND OUTLOOK
Vast territories might be affected by thaw subsi-dence. Bykovsky will serve as super-observatoryencompassing on-site monitoring for calibrationof various remote sensing approaches measur-
ing elevation change. Based on operational to-pography products such as from stereo VHR im-agery and TanDEM-X, we will expand this studyto larger, arctic-wide scales.
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