Permafrost related features such as: aufeis, tundra, thaw lakes and subsurface ice features were studied. LANDSAT imagery was used to measure the extent and distribution of aufeis in Arctic Slope rivers over a period of 7 years. Interannual extent of large aufeis fields was found to vary significantly. Digital LANDSAT data were used to study the short term effects of a tundra fire which burned a 48 sq km area in northwestern Alaska. Vegetation regrowth was inferred from Landsat spectral reflectance increases and compared to in-situ measurements. Aircraft SAR (Synethic Aperture Radar) imagery was used in conjunction with LANDSAT imagery used in conjunction with LANDSAT imagery to qualitatively determine depth categories for thaw lakes in northern Alaska

Hall, D. K.

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Technical Memorandum 82084
UTILIZATION OF REMOTE SENSING IN
ALASKAN PERMAFROST STUDIES
(NASA-TM-82084)	 UT1LiZAT10N of htrltUTlr
	
301-19528
SENSING IN ALASKA PEhMAYhOST ST O LUES (NASA)
14 p HC AOW/nt AU 1	 C SCL Jb,;
Uuclas
G 3/4 1	 1 bat 7
Dorothy K. Hall
cuc^J,4^- 
/; f0
FEBRUARY 1981 	 .
National Aeronautics and
Space Administration
Goddard Space Flight Cer:er
Greenbelt. Maryland 20771
UTILIZATION OF REMOTE SENSING IN
ALASKAN PERMAFROST STUDIES
Dorothy K. lull
Hydrological Sciences Branch, Code 924
NASA/Goddard Space Flight Center
Greenbelt, MD 20771
February 1981
4
GODDARD SPACE FLIGHT CENTER
GREENBELT, MARYLAND 20771
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1
iUTILIZATION OF REMOTE SENSING IN
ALASKAN PERIAAFROST'.STUDIES
3
Dorothy K. Hall
Hydrological Sciences Branch,
NASA/Goddard Space Flight Center
ABSTRACT
Using remote techniques, advances >>ave been made in studying many permafrost-related features
sucli as aufo.%, tundra, thaw lak(,', and subsurface ice features. Landsat imagery was used to
measure the extent and distribution of aufeis in Arctic Slope rivers over a period of 7 years, Inter-
annual extent of large aufeis fields was found to vary significantly, Digital Landsat data were used
to study the short-tern effects of a tundra fire which burned a 48 kin' Area in northwestern .Alaska.
Vegetation regrowth was inferred from Landsat spectral .reflectance increases and compared to
in-situ measurements, Aircraft SAR (Synthetic Aperture Radar) imagery has been used in con-
junction with Landsat imagery to qualitatively determine depth categories for thaw lakes in north-
ern Alaska, Finally, short-pulse radar has recently been used to locate and measure subsurface
permafrost features such as ice wedges, rce lenses and ice cores in pingos. For these and other
studies, the use of Landsat dita, SAR imagery and ,Short-pulse radar data has substantially in-
creased our knowledge of surface and subsurface processes operating within continuous uernia
frost.
9UTILIZATION OF REMOTE SENSING IN
ALASKAN PERMAFROST STUDIES
I
	 INTRODUCTION
Continuous permafrost underlies all or the Arctic Slope of Alaska, and discontinuous and
M
	
sporadic permafrost underlic most of the rest of Alaska. The presence of permafrost presents
unique proli!ems relating to eor ►struction, waste disposal, water supply and tramportation in Alaskv.
Many of the per nafrost-related features and processes which are relevant to these problems can lie
studied with remote sensing techniques. Sensors which operate in tho microwave portion of the
spectrum are necessary to augment the more readily available h1t'6rntatiov derivable from l.,ancls^:t,
mainly beeatise the m icrowa ve data have two distinct a dvantages over the visible: penet ration Into
the ground, and ability to "see" tbrough cloud cover, however, some advantages of I.uiclsat are
its repetitive coverage, its relatively good resolution (-80 tit) kind the substantial amount of data
collected (since 1972). In addition, the combined use of the visible and near-in-frared Landsat ^ ^ SS
(Multispectral Scanner Subsystem) data offers (11e opportunity to discriminate between wet and
d.ry areas of snow ankh ice.
()nly a few applications of remote sensing to permarrost studies Witt be disclissed in this 1141)m
although 1na11y ether studies have been performed, Studies are cited whicii involve the use of
Landsat imagery and digital data, aircraft SAR (syntllctic aperture radar) data and short-pulse radar
data, Distribution and variability oraufcis (overflow river ice), qualitative lake depth determination,
tundra recovery from wildfim and analysis of subsurrace permafrost features are discussed.
I
L.ANDSAT STUD11i.S OF A1JI'1 IS DISTRIBUTIO N AND EXTENT
111 areas of human activity in the Arctic, aufeis can pose a scrimis probiem, Aufels is a mass
of surface .ice formed by successive freezing or water that seeps from the aroun d, a fiver or a spring
tCarey, 1973), It can be detrimental to structures and trust be avoided during construction.
=turthernioro., poorly located roach cuts can create trufeis cohere there was none previously. Large
I
..r........«,.f^ ,.s,^k ..iL.^..^z^roc...	 ,. . r:..,u. `Bia.m^..	 .. d;,:ret^uw^.z^ru$e^:u^Tl.^^ w.. _,	 .._•wsuru,;;^c:,a..;.,,.,..^;.,^..
stream .mleis occurs in inost of the rners in northeastern Alaska. Distribution of aufcis and
changc% in the interannual extent of large aufcis fields have been monitored using I andsat MSS
,I.► ta ICIIII&1% et al., 1977. ILirdcn et al.. 1977 mid Mill, 10801. Stream aufcis occurs in approx-
miately tine same hart of a river channel c.ch year H hen the .aufcis is fed by a spring upstream from
.► potential constriction to streamllow. This is the rase in niany streams on the Arctic Slop, of
Alaska.
>istnhution of aufcis was determined f om L;rndsai Bind 5 (visihte) imagery. The viiible
Landsat hands are hest for tic form mat ion of auleis c\tent hccause its spring and sununer eood
contrast exists between the aufcis mid the surrounding snow-free tundra (Figure i ). The aul'6%
fields were transferred from I and%at images onto I :250.000 scale U.S.G.S. topographic snaps using
a Zoom Transfer Scope and then measured using a dot grid for the yeah 197:-1979. When mter-
annual variations in aufcis extent were compared with the incteorological variables which are
Figure 1. La idsat MSS Band S (V imblc ) Image
Showing Large River Auleis in Northeastern
Alaska. Area "A" is Aideis on the 1-chooka
River: Area "B" is A.ufeis on the Savnikviayak
Rner
r,a
believed to control aufbis extent, no statistically significant relationships were taund (Flai), 19130),
thus eMling into question the accepted theories oil aufeis formation.
Table l shows the extent of aurels on six Arctic Slope rivers for the years 1973-1979, late
to extensive clouts cover ill June of 1976 and 1978, very little atifes was visible ill these years.
Table I
Landsat-Derived Measurements of June Aufeis Extent ^knl`)
front. Selected Arctic Slope Rivers (1973 . 1979) (Front Ifall, 1980)
Canning Echooka linlahn la 	Konllaku t Sadlerocl l it Shaviovik
1975 16.69 18,31 21.94	 '2649 5.06 3.13
1974 4.44 '3.63 3.69	 27,31 5.31 3.81
1975. 10:44 26,69 15	 19,69 7.69 2.44
1976 ^°,	 __._ No data Available ror 1976
1977 21.81 19.63 3.50	 16.56 5.50 1.19
1978 ---- I No Dat„ `9.(x(1 -
1979 26.00 212.88 	 ,..._. -- No Data -- 6,88 4.2S
ORIENTED LAKE D1;^1'Tl-I DETERMINATION
Thousands of lakes on tilt* Arctic Slope of Alaska are oriented in .a north-northwest—south-
s u   theast direction. Whereas aufels is located preferentially in the eastern part of the Arctic: Slope,
the oriented l akes are predominately found in the western part, The dividing ` line' is the Colville
River. Small, less well-oriented lakes are found in the eastern, Arctic Slope. This type or dut y lake
is unique to permafrost because it corms from the thawing o1'ground ice in continuous permarrost.
Landsat is in excellent platform for studying the M7,e and distribution of the oriented lakes.
Landsat imagery is useful foe' qualitative d etermination of thaw ! ,like depth (Sellmaij et'al., 1975).
It has been observed even prior to Lundsat Vint deeper lakes retain their ice covers longer into the
3
i
summer than do shallow lakes. Three depth categorlea have been recognized; shal'io w (<1 in deep),
intermediate (1.2 in
	
and deep ( 2 in 	 based on relative date of summer ice cover dis-
sipation. Deeper lakes (with thicker ice) retain ice coveres longer into the summer than do shallower
lakes, The use of Landsat imagery has facilitated observation of the summer ice cover dissipation
and thus the categorization of lakes by depth..
During maximum ice thickness in April, aircraft SAR data have been used to classify the
oriented lakes into two depth categories: less than 2 in amid greater than 2 m deep. This is
possible using SAR data 'because; lakes which are riot frozen to their beds (i.e. where water is ,pres-
ent between the ice cover and the lake bed) are more reflective to the radar signal than are lakes
which are frortm to their beds. It is known that ice in these lakes obtains a maximum thickness of
approximately 2 in 	 the Arctic Coastal Plain of Alaska,
The real Dart of the dielectric; constant{c) of fresh water szz 80 and for ice e -^ 3,5 for soil
C.
 
!^-- 4,0. There is a high dielectric contrast in icc-covered lakes with water underneath the lee cover
(3.5 to 80) as coillpared to lakes which are frozen to their beds (3.5 to 4,0). This high dielectric
contrast  t ee	 te r a	 ice contributes to the high radar returns	 'ea lakes but doe 1be we n►^aw_ ►  nd	 ► 	 }	 	 _ 	 t r  to de p 1 	 ^ ► at
r
	
	
fully explain these bright returns, According to Weeks et al. (1978), elongated air bubbles at the
ice water interface act as scatterers to the ,radar signal and contribute to the high radar reflections
in the deep thaw lakes, Used together, April SAR imagery and summer Lail dsat imagery are useful
for qualitative determination of lake depth. Lake depth information is useful for several reasons.
First of all, there is a shortage of freshwater in the ,Arctic during the winter. Settlements and
w
	
	
construction teams must rely oil 	 lakes (not frozen Go their beds) for their water supply
in the winter. Furthermore, lakes known not to freeze to the bottom could be stocked with fish
3 for fond supply (Weeks ct al., 1978).
Moving equipment and supplies in the Arctic is logistically easier during, the winter when the
ground is frozen solid. In the sonimer, severe damage to the tundra may result from improperly
4
tr%ansporting materials, strict
	 Thus, hi spite of' the colO, its 	 ways it is advantageous to
work during, the winter.
TUNDRA RECOVIiRY FROM WILDFIRE
The tundra is a delicately balanced system which is vulnerable to the vagaries or climate and
man, Tundra is u treeless expanse of vegetation rom66 above the trecline In Arctici and Alpine -areas,
Fire iii  part of th natural ecological balance of the tundra (Vicreck, 1973). However, the effects
of eau;t-ol fires on tlje tundra are not well understood (Brown and Crave, 1978). By inereasinl y our
under43nding of the recovery of tundra following Y( wilame, we call gaii Nonsisllt into the dynaniloi
orperrmif'rost and its capacity for recovery following disruptions cimscd by man
I undsat data Dave been used to locate and monitor wildfires in Alaska (Haugem ekil- 19721
and 11all et al., 1978), Recently, Landsar digital data haw,- been used to monitor the short-term
recovery or tundra following a rim in northwestern Alaska by Thall eta',. (1980,q),
During the summer of 107 a drought rendered the tundra in northern Alaskavidnerable to
lightning-induced wildfires (Ernst and Matson, 1977). One such fire burned a 48 km" patch or
tundra near the Kokolik River in northwestern Alaska. U.S. Army Cold Regions Research and
xinvering Laboratory (C.RRI-L) scientists landed at the site of the fire after the burning had
ceased to make observations (Ilall et al, 1978).
Lan dsat NISS data were acquired before, during and directly after the rav, and approximately
one year aster the tire (August 1979), Us 	 the GSI-C Atmospheric and Oceanographic Imagm
Processing System (AOIPS). the Kok-olik River burned area was extracted trom a full L-mi6at scene
and onlarged, Three hurn severity CatCVOriCS (FigLire -2 ) were iniVrred rrom Landsat spectral response
UILICS (digital counts ranging from I to 2.56) and from comparison or the Landsat data with in-situ
field measurements,
it
	
5
I	 u., ^	 Subsccnc tit' an August :I . P) ; % L. ► nkl,at -SLcnc of the
hokolik River Burned Area Classified (hgitalh Into I lircc liurn
Sever ► fy Categories
An August 1978 suhsccnc was also analyred. Resulfs showed t hat there were s ► pnifi.ant
increases in spectral reflectance wit hm the three areas of hurn .cverit% H h ► ch were determined from
the August 1977 subscene (Table 2). Thi:c corroborated in-situ nk asurements by CRRFL scientists
which indicated suh.tantial vegetation regrowth in the one year period fallowing the fire I Ilall et al..
1980a). f ligher spectral reflectances are indicative of more vegetation. In fact, sor-; lightly burned
areas appeared fully re,.overed by August 1978 based on Landsat spectral response and in-situ
measurements of vegetation.
Tundra fires can have significant impact on the hydrology of flit- tundra. If a fire occurs
fallowing it prolongec drought, intense huming can result and the permafrost can be stripped of its
insulative cover of vegetation. Thawing of scar-surface ice can occur :ond cause considerabie amounts
of water to he released and result in thvi-mal erosion which %ill im:rease each sunnier until a nc"
thermal equilibrium is established and the vegetation regenerates (Brown. 1970).
6
Table 2
Percent Increase in Spectral Reflectance Between
August 1.977 and August 1978 Used to Infer Increases
In Dive Grouatd Cover (after hall et al,, 1980a)
Mean Digital Counts, x
Burn Severity
Categories 1977 1978 ?ercent Incrose
Severe 8 13 62,$
Moderate 21 30 4:3.0
Light 30 46 53.0
SUBSURFACE PERMAFROST FEATURES
Tundra surface disturbances that affect construction and transportation are a result of slump-
Ing of the ground surface in response to 4 thernial erosion` or meltingo r  ice-r!cli permafrost. Ice-rich
permafrost contains such features as ice wedges and ice lenses. Ice wedges are vertically-oriented
masses of ground ice caused by surface water (from snownielt) seeping into thermal contraction
cracks in the spring in permafrost; and freezing in the winter over thousands of years. ice lenses
are masses of ground .ice which form parallel to the surface as a result of moisture tilling in interstices
in fine-grained soils, Until recently, airborne remote sensing could only be used to infer subsurface
conditions from surficial expressions. It now appears ,promising that the use of a short-pulse radar
operating at a frequency of 480 M14z may be useful for detecting and measuring subsurface perma-
frost features. This radar system has been flown experimentally over the proposed Alaskan gas
pipeline right-of-way on a helicopter in order to investigate the ground in which the pipeline will
Y
be placed (Hall et al., 1980b)3
Subsurface penetration of approximately 3 m was achieved and signatures of ice wedges, ice
lenses and pingo ice cores were observed, (Pingos are conical-shaped features which form in perma-
frost and are generally ice-cored in the continuous permafrost region,) Linear features having bright
7 1
returns wore found to extend approximately 3 of below the ice cores of bingos. Similar bright
Iincxar features were seat beneath frozen Mes. In addition, the location and distribution of icc
wedges were determined and ice wedges were measured,
Tile short-pulse radar data were found to be very useful l ot de termination of subsurflce
hoillogencity. A very homogoneous orca ma y o ily require one borcbr)lc for investigation,, while
an i111tonrogelreous area (as determined from (lie short-pulse radar data) may require several bore.
holes to detcrinhic the condition of the subsurface so that const-:lotion play begin. Boreholes are
,eery expensive to drill, and they disrupt the tundra and permafrost. It is flivrefore advantageous
ic, limit boreholes to a minimum if the needed.. geophysical. information call be acquired in other
,w,I y t,.
CONCLUSION
Since tilt advent or remote wring, much progress has been made in studying the perlglaciai
a»xxxir0.x ,a,.aa,.}	 a.a.	 s! ''	 i.	 J i._	 t_g- a a
a_ 
	
r r
>..t.. x a.JA,k"+6. Ta_44: t anc H'a ery lli'. Wen iIaCU eC7 4I^taS 	 thaw(;1 ►;es bawd t711 ti17e. t(ieilf Ull, degree.l"'
or orientation and depth, and to determine spatial and temporal, variability of many features and
processes such as aufols, and to monitor the extent and recovery= of tundra fires. The use of air-
craft Slit data and short-pulse radar, data has enabled us to "see" beneath the surface in ordenr to
study thaw lakes and subsurfcfee permafrost features. Oftentimes, tile use of sensors operating in
cdirrerent parts or the spectrum is necessary to augment incsitu data. In addition. it is far less disrup-
tive to the permafrost and overlying tundra if'geophysical I nforn ation call be obtained remotely.
.
f
1
,
8
REFERENCES
Brown, R, J. E,, 1970: Nature of Permafrost, Permafrost In Canada, Univ. of Toronto Press,
pp, 1.30,
Brown, J. and N. A. Grave, 1978: Physical And Thermal Disturbance and Protection of Permafrost,
!'roc. Third hiternatlonal Conference on Permafrost, 10.13 July 1978, Edmonton, Alberta,
Canada, 41 pp,
Carey, K, L„ 1973: Icings Deueloped from Surface Weterantl Croun(I Water. CRREL Monograph
I l i•D3, 65 pp,
Childers, J. M., C. E, Sloun, J. P. Meckel and J. W„ Nauman, 1975: Hydrologic Reconnaissance of
the Eastern North Slope, Alaska, 1975. U.S. Dept. of the Interior, Geological Survey Open-
File Report 77.492, Anchorage, AK, 65 pp,.
Ernst, J, A. and M. Matson, 1977: A NOAA-5 View of Alaskan Smoke Patterns, Bul: outer, Alet.
Soo„ V. 58, No. 10, pp. 10741076,
Mall, D. K., J. Brown anr4, L. Sphnson, 1978: The 1977 Tundra Fire in the Kokolik River Area of
Alaska, Arctic, V, 31_, pp. 5458,
Hall, D. K., 1980: Analysis of the Origin of Water Which Forms .Large Aufels !<lelds on the Aretic
Slope of Alaska Using Ground and Landsat Data, Ph, D. Dissertation, Univ. of Maryland,
124 pp.
Hail, D. K., J. P. Ormsby, L. Johnson and J. Brown, 1980a: Landsat Digital Analysis of the Initial
Recovery of Burned Tundra at Kokolik River, Alaska, Rem. Sensing of Environ, v. 10, pp.
263.272.
9
to
we-
flail, 1) K.. J. F. McCoy, R. M. Carneron, P. van R tten 
and 
hl. U". Station, 19801: 1 	 Sensing
of Arctic Hydrologic Processes. Prov. of the Third (b1loquittin nit Planetary 11 14ter, Niagara
Falls. NY.
Harden. D.. P. Barnes and U.. Rehmiltz, 1977.- Distribution and Character of Nalvils in Northeastern
Alaska, Arctic, V. 30, No. 1, pp. 28.40,
11augm, It. K,. McKim, If. L., Gatto, L. W. and Anderson, D. M., 1972w: Cold regions unvironjuental
analysis based Oil 11I TS-1 imagery. Proc"dings, highth	 nit Rmv)w
&IIShig of Environment, 19 1-Z Ann Arbor, Michigan: 13mvirunmental Research institute or
Michigan. Vol, .". pp. 15 11 - 15*411.
I lolingren. B., C. Benson and G. Woller, 1974: Al(teh as Obserred by 1-7M. Contract report to
National Aeronautics and Space Mministration by Univ. of Alaska Geophysical Institute,
1113. (10-82.
O'Lone. R. G., 1975- Alaskan Air Support Facing Challenges, A Wation It 	an(I Sluice Technology.
V. 103. pp. 14-17.
S,.Ahmin. P. V., J. Brown, 11. 1. Lowellen, 11. McKim and C. Mcrry, 1975: The Classification and
Geomorphic Imptivations of Thaw Lakes on the Arvile Coastal 1-1 aht, Alaska, CRIZE11, RR 344.
pp.
Viereek. L. A., 197.3 , Wildfire 
in 
the Taiga of Alaska, Quaternary Res., V. 3, pp. 465-495.
.0Wvvks, W. R^ A. 0. r untain, M. J.,, Uryan and C. Ulac hi, 1978: 01friewnees in Radar Return from
lee-Covered North Slope Likes. JG4JR, V. R3, pp. 4069.407 3.
1^
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Utilization of remote sensing in Alaska permafrost studies

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