International Journal of Geosciences, 2012, 3, 339-348
http://dx.doi.org/10.4236/ijg.2012.32037 Published Online May 2012 (http://www.SciRP.org/journal/ijg)
Is Isostatic Rebound in Slow Spreading Gakkel Ridge of
Arctic Region Due to the Climate Change? A Case Study
Arun Kumar, L. Sunil Singh
Department of Earth Sciences, Manipur University, Imphal, India
Received December 31, 2011; revised February 22, 2012; accepted March 23, 2012
ABSTRACT
Ny-Alesund, Swalbard region which is located in the mid-ocean ridge of the Arctic Ocean, and named Gakkel ridge, is
the slowest spreading ridge of the global system. In the present study an attempt has been made to associate isostatic
rebound using GPS campaign data collected at Ny-Alesund area. The Artic Region Campaign GPS network was estab-
lished in 2009. The network consists of three campaign mode station. The distance between GPS point is about ~30 km.
The preliminary results of our investigation appear broadly consistent with the recent tectonic activity in western Sval-
bard. The resultant velocity vector is 14.84 mm·yr–1 with an azimuth of 27.67˚N and a vertical displacement of 7.62 
3.0 mm·yr–1 is estimated in Swalbard, in which we presume Glacial Isostatic Rebound (5.1 mm·yr–1) and post glacial
geological process (Present Day Ice Melting, erosion, and shore line deposits) of 2.52 mm per year in the study area.
Keywords: Isostatic Rebound; Artic Region; GPS Processing; Crustal Deformation
1. Introduction
Much of Northern Europe, Asia, North America, Green-
land and Antarctica were covered by ice sheets during
the last glacial period. The ice was as thick as three kilo-
metres about 20,000 years ago. The enormous weight of
this ice results in the deformation of the Earth’s crust and
warp downward, forcing the visco-elastic mantle material
to flow away from the loaded region. At the end of each
glacial period when the glaciers retreated, the removal of
the weight from the depressed land led to slow (and still
ongoing) uplift or rebound of the land and the return flow
of the mantle material back under the deglaciated area.
Due to the large viscosity (3 × 1021 P) [1] of the mantle,
it will take thousands of years for the land to reach an
equilibrium level.
Several studies have shown that the uplift has taken
place in two distinct stages. The initial was near-instan-
taneous due to the elastic response as the ice load was
removed. After this elastic phase, uplift was slow due to
viscous flow and the rate of uplift decreased exponen-
tially. Today, typical uplift rates are of the order of 1
cm·yr–1 or less. In northern Europe, this is clearly shown
by the GPS data obtained by the BIFROST GPS network
[2]. Studies suggest that rebound will continue for at
least another 10,000 years. The total uplift from the end
of deglaciation depends on the local ice load and could
be several hundred metres near the centre of rebound.
Recently, the term Post-Glacial Rebound is gradually
being replaced by the term glacial isostatic adjustment.
This is in recognition that the response of the Earth to
glacial loading and unloading is not limited to the up-
ward rebound movement, but also involves downward
land movement, horizontal crustal motion [2,3], changes
in global sea levels [4], the Earth’s gravity field, [5], in-
duced earthquakes [6] and changes in the rotational mo-
tion [7].
2. Gakkel Ridge
The Gakkel Ridge (formerly known as the Nansen Cor-
dillera and Arctic Mid-Ocean Ridge) is a mid-oceanic
ridge, a divergent tectonic plate boundary between the
North American Plate and the Eurasian Plate. It is lo-
cated in the Arctic Ocean between Greenland and Siberia
(Figure 1) with a length of about 1800 kilometers. Geo-
logically, it connects the northern end of the Mid Atlantic
Ridge with the Laptev Sea Rift. Gakkel ridge is the slowest
spreading ridge of the global system of mid-oceanic rid-
ges with full spreading rates declining from about 12.5 to
6 mm·yr–1 from west to east [8]. The existence and ap-
proximate location of the Gakkel Ridge was predicted by
a Soviet polar explorer Yakov Yakovlevich Gakkel and
discovered by Soviet Arctic Expeditions in the late for-
ties—early fifties of the 20th century. The Ridge is named
after him.
Seismotectonically, the Gakkel is active as evidenced
by the presence of earthquakes of magnitude > 3.5 at
C
opyright © 2012 SciRes. IJG

A. KUMAR, L. S. SINGH 340
Figure 1. The Gakkel Ridge.
shallower depths than 30 km. They caused the slope fai-
lure in regions of unstable methane hydrate and further
cause giant plumes of methane to be released and enter
the atmosphere. Earthquakes have been increasing in fre-
quency and magnitude along the Gakkel Ridge and peaked
in frequency in 1999 when there were 252 measurable
earthquakes with magnitudes as high as 4 to 6. These
earthquakes were initially focused at the crust—mantle
boundary, 16 to 20 km.
The earthquake activity was apparently associated
with magma ascension along the down but then rose up
to the magma conduit ridge and the subsequent subma-
rine explosive volcanic eruptions. Fault activation due to
the magmatic emplacement covered a very wide region
[8]. The peak yearly frequency of magnitude 4 to 6 earth-
quakes on the Gakkel Ridge is mirrored by a major peak
in worldwide Great and Major Earthquakes (>Magnitude
7) and a peak in the atmospheric methane. Therefore
Gakkel Ridge magma emplacement earthquakes, Arctic
subsea explosive volcanicity and fault activation over a
wide area is clearly directly linked to the destabilization
of the submarine slope Arctic methane hydrates and re-
lease of abundant methane to the Arctic atmosphere.
3. Geology & Tectonics
Svalbard is located in the north western corner of the
Barents Shelf (Figures 2 and 3). The archipelago repre-
sents an uplifted part of this otherwise submerged shelf.
The uplift was most extensive in the north and west,
leaving progressively older rocks in these directions.
A pronounced synclinal feature, the Central Spitsber-
gen Basin, occupies most of central Spitsbergen. The basin
is bounded to the west by the West Spitsbergen fold-and-
thrust belt, which die out towards the eastern part of
Spitsbergen. The basin boundaries parallel a dominant
NNW-SSE structural grain on Spitsbergen comprised
through four similarly aligned episodes of tectonic defor-
mation.
Ny-Alesund is located in NW Spitsbergen of Svalbard
archipelago in the Arctic Ocean. It provides varied geo-
logical structures and geo-historical development since
the palaeo-Proterozoic time and is well known for having
rocks of all the geological ages with multi orogenic de-
velopment and prominent tectonic events [10,11].
The last recognised important tectonic event in this
area is dated from the late Tertiary, [12], when sediments
of the Ny Ålesund tertiary basin have been overthrusted
by older, carboniferous rocks. From this late Tertiary
event onwards, the area of Ny Ålesund (western Svalbard)
is supposed to have mainly been affected by post-glacial
rebound processes.
Plag H. B. [13] of Norwegian Mapping Authority sug-

A. KUMAR, L. S. SINGH 341
gested that Western part of Svalbard, despite its nearness
to the Mid-Atlantic ridge, is on the stable part of the
European Plate. Tomasai and Rioja [14] further sup-
ported the idea evident by small base line changes be-
tween Ny-Alesund and Wettzell. However, in more re-
cent times, high heat flow anomalies and a sparse seismic
activity have been recorded from offshore western Sval-
bard [15], suggesting that this province and its adjacent
onshore continuation could still be tectonically active
domains. Bockmann [16] reported indicate neo-tectonic
movements and a possible small scale tectonic movement
from the results of GPS campaign data in the region.
This region is usually considered to be stable from the
plate tectonics standpoint. But if this is true for continen-
tal Scandinavia the situation of Svalbard is quite different.
The western Svalbard fold-and-thrust belt has a complex
tectonic history linked to the opening of the Northern
Atlantic Ocean. This area is located close to the Horn-
sund Fault Zone, one of the major active fault zones dur-
ing the separation of the NE Greenland and Svalbard-
Barents shelves. The last recognised important tectonic
event in this area is dated from the Tertiary [12], when
the Ny Ålesund Tertiary basin has been overthrusted by
carboniferous rocks (Figures 2 and 3). But western Sval-
bard is located only 150 km far from the Knipovich
Ridge, which is considered an active segment of the Mid-
Atlantic Ridge system. High heat flow anomalies and
considerable seismic activity (Figure 4) have been re-
corded from offshore western Svalbard [15] showing that
the area is tectonically active and in the Kings Bay area,
minor seismicity may indicate some neo-tectonic activity.
During Pleistocene time this area was covered by a
thick ice sheet. The entire region is now affected by a
post-glacial rebound as result of isostatic response to the
melting of the ice shield about 10,000 years ago. This
phenomenon induces an obvious vertical motion but also
a tangential deformation with horizontal displacement at
the transition between the central dome and the fore-
bulge area. (Geological data based on raised shore de-
posit give 3.3 mm·yr–1 uplift at Kvadehuksletta west of
Ny Ålesund [11] during the last 9 kyr, and 2.8 mm·yr–1
uplift at Recherche Fjord [17,18]. Furthermore massive
erosion of the Svalbard linked to glacial and post-glacial
geomorphological processes, leads to mass redistribution
and may increase the post-glacial effects (raised shore
lines). [11,19,20]: ~330 km3 sedimentary wedge offshore
Isfjorden between 200 ka and 13 ka (rate: ~7.9 × 106
m3·a–1).
Gakkel spreading Ridge is seems to be slow spreading
ridge and the Svalbard areas are located south of the
ridge, which shows the evidences of mainly local defor-
mations along faults and part of it can be accommodated
in the isostatic rebound due to climate change activities.
The aim of this study is to carry out a preliminary defor-
mation analysis using the GPS campaign data from years
2009-2011 to resolve local deformation expected in the
course of the glacial induced isostatic rebound (Figure 5).
4. Network and GPS Measurements
In order to carry out the crustal deformation studies of
Artic Region a geodetic network comprising of three
Figure 2. Plate configuration in the Arctic prior to opening of the Atlantic and the Polar Basin [9].

A. KUMAR, L. S. SINGH 342
Figure 3. Simplified geological map of Svalbard [21].

A. KUMAR, L. S. SINGH 343
Figure 4. Location map of GPS campaign site at Arctic Region.
stations (Figure 4 and Table 1) has been established.
The first GPS campaign measurements were initiated
during August 2009 with the establishment of three sites,
Ny-Alesund (ALDM), Western tip of Ny-Alesund (ETAL)
and Eastern tip of Ny-Alesund (TALS) of Artic. These
GPS campaign stations are equipped with Leica GX1200
GPS receivers with choke ring and Zephyr geodetic an-
tennae. All the sites selected are in the open area on the
ground. The distance between two GPS point is about 30
km.
5. Monumentation
The Monumentation normally set eventually will become
unnecessary when active control networks have been est-
ablished. Things to consider when establishing monu-
mentation include precision and environment. If high
precision (<1 cm), repeatable results are desired, the
mark itself should be 1 mm in diameter and the marker
should be durable and stable in its medium. All markers
should be resistant to weathering, but the type of marker
used may be dictated by land use.
Campaign geodetic monuments for each campaign site
were set up using small drilling machine. The hole about
1/2" deeper than the pin, the preferred method is to
achieve a friction fit between the pin and the rock. The
hole tends to widen near the top, because the bit pivots
about its tip early in the drilling. Drill the hole, and blow
all dust out of the hole with a long flexible tube. And
check how far the pin will fall into the hole. Stainless
brass pin about 3/4-inch pin were anchored into the holes
using epoxy.
Data at these sites were recorded with conventional
30-second samples continuously for more than three
day.
6. GPS Processing
The GPS data obtained from the campaign site has been
converted into RINEX observation files and quality check
has been performed using TEQC (Translation, Editing
and Quality Checking Software). The quality check plots
of all the GPS data were carefully examined and the data
with high cycle clips were carefully examined and the
data with high cycle clips multipath and <12 h observa-
tion were removed from the analysis.
The GPS data were processed using the GAMIT/
GLOBK [22,23] software package. In addition to the
GPS data collected from study area, we processed data
from a number of International Global Navigational State-
lite System Service (IGS) permanently operating stations
(Figure 6) in and around the region (dav1, hofn, kir0,
mawl, nril, nyal, nya1, reyk, scor, tro1,vesl). We com-

A. KUMAR, L. S. SINGH 344
Table 1. GPS campaign stations (WGS84: Geodetic-unprojected).
Sl. No Name Identifier Latitude Longitude Height (m)
1 Ny Ålesund ALDM 78˚55'38.11'' 11˚56'14.14'' 33.46
2 Western tip of Ny Ålesund ETAL 78˚52'17.66'' 12˚25'48.48'' 65.98
3 Eastern tip of Ny Ålesund TALS 78˚58'23.49'' 11˚28'28.38'' 42.42
Figure 5. GPS monument at ALDM.
Figure 6. IGS stations used in the proce ssing.
bined our own solution with daily solutions of global IGS
stations processed and archived at the Scripps Orbital
and Permanent Array Centre (SOPAC). The International
Terrestrial Reference Frame (ITRF) 2005 [24], was de-
fined by applying translation and rotation parameters that
minimize the horizontal velocities of sites assumed to lie
within the stable plate interior.
7. Results
Figures 7 and 8 shows the computed GPS velocities and
the series plot of the campaign sites respectively. The
resultant vector of TALS is more than ALDM and ETAL.
The maximum and minimum root mean square (RMS)
errors are 0.003 m and 0.001 m respectively. The small
values of RMS indicate the results obtained are precise

A. KUMAR, L. S. SINGH 345
Figure 7. Estimated velocity plot along with the major tec-
tonic features in and around Ny Ålesund ar e a .
and reliable. It is readily seen that the RMS statistic is
very well behaved and that there is no tension as each
day of observation is added to the next. In particular
there is no tension for the campaign data between the
2009, 2010 and 2011. This means that the detected
movement at stations, ALDM, TALS an ETAL was well
determined. However with only three surveys performed
so far there is insufficient evidence.
8. Discussion
We also compared our results with secular displacement
and gravity rates observed in the Swalbard region where
the Predicted Present Day Ice Melting rate of 2.04
mm·yr−1 for the nominal melting rate of −47 cm·yr−1
gives a uplift rate of 5.1 mm·yr−1 that is consistent with the
observed rate of 5.2 ± 0.6 mm·yr−1 [25]. It can be con-
cluded from the above discussion that there are local de-
formations along existing faults, which seems to be ac-
tive. The resultant vector of Ny-Alesund (ALDM) is 14.84
mm·yr−1 with an azimuth 27.67˚N with a vertical displace-
ment of 7.62 ± 3.0 mm·yr–1, which is not due to only the
isostatic rebound. It is necessary to consider the effects
of upper mantle viscosity, which may give some errors in
the estimates of the vertical uplift due to the post glacial
isostatic rebound. There was an attempt [24] in 2006 to
estmate the viscosity at study area and gravity rates. The
gravity rates are –2.5 µ·Gal·yr–1 and the corrected rates
of sea level rise correspond 20% - 30% error. For the
verti- cal component, the ice model effect [24] give a
similar rates 1.2 - 1.9 mm·yr–1 and –0.3 µ·Gal·yr–1 with
nominal upper mantle viscosity value assumed for their
study. We have compared our rates of uplift with the
earlier studies [24], in which 5.2 mm·yr–1 and gravity
rates –2.5 µ·Gal·yr–1 and viscosity rates for vertical com-
ponent are 3 mm·yr–1 and –1.9 µ·Gal·yr–1. We consid-
ered the possi- bilities of other discrepancies due to
various geological processes such as raised shore line
deposits and high ero- sion rates (Figure 9) at Ny Ale-
sund [26-29]. There is possibility that massive erosion at
Svalbard led to mass redistribution that may enhance the
post glacial rebound effect. After the consideration of the
effect of geological processes, their rates are estimated
[24] as 3.1 mm·yr–1. The predicted post glacial normal
ice melting of the 2.04 mm·yr–1 for normal melting of
–47 mm·yr–1 gives an uplift rates of 5.2 mm·yr–1.
The vertical uplift rates (PGR) are also measured in
Green land in Sisimint and Disco Bay (1.6 mm·yr–1),
which is located east of the Gakkel Ridge [30]. The re-
gion is affected by the retreat of ice margin during the
last 150 yr. The present day sea level rise is 4 mm·yr–1 in
the outermost part of the Greenland.
The most recent results obtained by different geodetic
techniques (VLBI, GPS) show a motion of the Ny Åle-
sund station up to 6 mm/yr. in vertical component, that
cannot be explained by post-glacial rebound only. The
investigation on the stability of the site combining both
structural geological and classical geodetic techniques is
made at NyAlesund [31]. For this purpose, an integrated
geodetic network (spirit levelling and GPS) was estab-
lished and measured in July 2002, in order to verify the
stability of VLBI antenna site. The Preliminary results of
our investigation appear broadly consistent with the hy-
pothesis of active, or at least very recent tectonic activity
in western Svalbard.
Based on the various comparisions from the earlier
studies, our results of uplifting of the NyAlesund is due
to the post glacial isostatic rebound as well as various
geological processes also contribute to the high ice melt-
ing. If confirmed by further work, this finding may yield
relevant constraints to an enhanced understanding of the
recent tectonic evolution of the arctic region. We may
infer that these GPS data reveal the process of climate

A. KUMAR, L. S. SINGH 346
Figure 8. Time series plot of the campaign sites.
can correctly reflect the conditions present at arctic re-
gion. There are local deformations along existing faults,
which seems to be active. The short time span of the ob-
servations includes only three epochs of GPS campaign.
The resultant vector is 14.84 mm·yr–1 with a azimuth
27.670˚N, a vertical displacement of 7.62 ± 3.0 mm·yr–1,
which seems to be a higher estimates for isostatic re-
bound only at Arctic region. The geodetic observation
around Fenno-scandian Shield suggest the 0.5 mm·yr–1,
which indicate a lower rates of rebound due to the less
extent of snow cover and seasonal changes during the
years of observations. Our results are within the estima-
ted rates of vertical displacement 12.5 to 6 mm·yr–1 from
west to east [7]. Both poles have ice sheets, which exert
more stress in the isostatic rebound. We need to continue
more observations of GPS campaigns to rectify the errors
for precise results. Since, Svalbard archipelago consists
of number of islands, a carefully designed follow-up mi-
cro-earthquake activity in the Svalbard region is neces-
sary to correlate the deformation rates with tectonic and
glacial quakes in order to derive the best estimates for
isostatic rebound, which is due to the snow melting vis-
a-vis climate change.
Figure 9. High erosion rate s at Ny Alesund.
change, which is responsible for the isostatic rebound
due to the snow melting phenomenon.
9. Conclusion and Future Work
The results presented in this research are preliminary at
best and do indeed need a fourth epoch so that the results

A. KUMAR, L. S. SINGH 347
10. Acknowledgements
The work is carried out at Arctic Region with the finan-
cial assistance provided by National Centre for Antarctic
& Ocean Research, Ministry of Earth Sciences Govern-
ment of India is gratefully acknowledged. Authors are
thankful to Dr. Vineet Gahalaut, Scientist NGRI for pro-
viding his valuable suggestions for the preparation of the
manuscript.
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