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Iceberg calving from the Antarctic Nansen Ice Shelf in April 2016and its local impact
Tian Li • Yifan Ding • Tiancheng Zhao •
Xiao Cheng
Published online: 25 June 2016
� Science China Press and Springer-Verlag Berlin Heidelberg 2016
Owing to global warming, frequent ice shelf disintegration
and rapid acceleration of inland ice flow have occurred in
recent decades, which impacts the Antarctic mass balance
and the global sea level [1]. These events are closely linked
to atmospheric and oceanic processes. The prolonged melt
season and larger extent of melt ponds on the ice shelf
surface [2], as well as enhanced basal melting caused by
warmer sea water [3], will induce crevasses that expand
and enhance fracturing of Antarctic ice shelves. The calved
icebergs comprise a massive fresh water reserve, and ice-
berg evolution can affect ecological and oceanic environ-
ments, such as phytoplankton blooms, the fresh water
balance in the Southern Ocean and the growth and decay of
local sea ice, especially the alongshore fast ice [4].
Antarctic scientific research expeditions will also be
affected.
The Nansen Ice Shelf (NIS, 163�280E, 75�50S) is locatedon the west side of Terra Nova Bay (TNB) and abuts the
north side of the Drygalski Ice Tongue (DIT) in Victoria
Land, East Antarctica [5]. The NIS flows into TNB from
the grounding line at the flow branch of the Reeves Glacier
for approximately 45 km to the front and is approximately
35 km across between the southern boundary and Inex-
pressible Island, which is the potential site for the next
scientific station of China. On April 7, 2016, the front of
the NIS calved into two medium-sized icebergs—C33
(21 km 9 8 km, C33 is named by the National Ice Center,
which records icebergs with minimum lengths of 18.5 km)
and C33b (10 km 9 5 km, C33b is named based on the
National Ice Center principle for this paper) owing to the
large expanding crevasse. The calving area is approxi-
mately 203 km2 with an average thickness of 200 m, and
the mass loss is approximately 37 Gt, as calculated from
Sentinel-1A SAR data and Cryosat-2 radar altimetry pro-
files. After calving, the two icebergs drifted with melange
attached, which once filled the large crevasse.
Owing to the combined effect of basal melting and the
strain rate distribution, the crevasse in the calving event
initially formed in the central part of the NIS and was
approximately 6.5 km from the coastline. Its length sig-
nificantly expanded (north–south trending) from 2011 to
2013 at a rate of 6.6 km/year, as calculated from Envisat
ASAR, Landsat7 ETM? and Landsat8 OLI images; it
appeared as meandering threads in the north–south
direction. From 2013 to 2016, the width of the crevasse
expanded (east trending) owing to ocean current, wind
and hydraulic pressure [2]. The widest part prior to the
NIS calving was 1.7 km, according to Sentienl-1A SAR
data.
The drifting routes of the two icebergs are shown in the
Fig. 1a. The two icebergs C33 and C33b drifted along the
Antarctic coastline driven by ocean currents and winds
[6, 7]. They collided prior to April 9, 2016. Combined with
Coriolis forces, the iceberg C33b drifted towards the
coastline and became stranded on the east side of Abbott
Mount on April 14, 2014. This occurrence was caused by
the iceberg draft with respect to the ocean water depth. The
average thickness of iceberg C33b is approximately 200 m
as calculated from CryoSat-2 profiles, and the average draft
of the iceberg is estimated to be 178 m according to a
T. Li � Y. Ding � T. Zhao � X. Cheng (&)
State Key Laboratory of Remote Sensing Science, College of
Global Change and Earth System Science, Beijing Normal
University, Beijing 100875, China
e-mail: [email protected]
T. Li � Y. Ding � T. Zhao � X. ChengJoint Center for Global Change Studies, Beijing 100875, China
123
Sci. Bull. (2016) 61(15):1157–1159 www.scibull.com
DOI 10.1007/s11434-016-1124-9 www.springer.com/scp
hydrostatic equilibrium equation; this draft is larger than
the water depth calculated from Bedmap-2 bed elevation
data near the coast of Abbott Mount (Fig. 1b). Abbott
Mount can serve as a natural barrier for the stranded ice-
berg as it can impede the strong katabatic wind from the
surrounding glaciers. Regarding iceberg C33, it freely
drifted to the Washington Cape on April 21, 2016. Iceberg
C33 has two inferred routes when it leaves the Ross Sea in
the future. The first route consists of drifting westwards
with the Antarctic Coastal Current, and the second route
entails drifting northwards away from the Antarctica owing
to the effect of Ross Gyre [6].
For the NIS calving event, the real risk is the
potential increase in the local fast ice extent owing to
the influence of the stranded iceberg C33b [8]. Fast ice
is a type of stationary sea ice that is attached to coastal
features, such as coastline, grounded icebergs, and an ice
wall or ice front, and forms in sheltered coastal
embayments [4]. Thus, the extent of fast ice is closely
related to terrain changes, and the stranded iceberg C33b
serves as an anchor site for fast ice growth. After iceberg
C33b was stranded on the Abbott Mount coast, fast ice
rapidly reformed by attaching to the iceberg’s sidewall
and coastline in less than 10 d (Fig. 1b). The fast ice
extent is expected to increase during this austral winter.
Compared with the maximum fast ice extent of this
region in 2015 (Fig. 1c), the possible fast ice extent this
year is expected to spread from the east of Campbell
Fig. 1 a Bathymetric map of the Ross Sea with the drift routes of icebergs C33 and C33b. The background is a Sentinel-1A SAR image that was
acquired on April 18, 2016 with a spatial resolution of 40 m. The bathymetric data are derived from Bedmap-2 bed elevation data with a
resolution of 1 km. The calving part of the Nansen Ice Shelf is delineated with a blue line. Iceberg C33 is delineated with a white line. Iceberg
C33b is delineated with an orange line. b Fast ice extent around iceberg C33b on April 21, 2016 with isobaths overlaid. c Maximum fast ice
extent observed in winter 2015
1158 Sci. Bull. (2016) 61(15):1157–1159
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Glacier Tongue to the east of Inexpressible Island and
extend approximately 3.5 km outward.
The worsening fast ice condition in this region can have
a severe impact on the research activities of nearby sci-
entific stations (Mario Zucchelli Station of Italy, Gond-
wana Station of Germany and Jang Bogo Station of Korea)
and the migration and foraging of penguins. If the fast ice
continues to grow southward, it will create new challenges
for site selection for construction of the new scientific
research station of China, which was planned on the
Inexpressible Island. The calving of the NIS may cause the
disintegration of melange that filled the north coast of the
DIT and decreases its support on the north side. Additional
crevasses are expected to appear on the southern side of the
DIT in the near future.
Our report can provide additional information for the
new scientific research station of China and early warnings
for nearby scientific research activities. In future studies,
we will monitor the local fast ice extent and iceberg
stranding state and analyze the potential impacts of this
calving event.
Acknowledgments This study is funded by the National Basic
Research Program of China (2012CB957704), the National Natural
Science Foundation of China (41176163), the Specialized Research
Fund for the Doctoral Program of Higher Education (201200031
10030), the Strategic Research Fund Program of Polar Science
(20140301), the Project of International Cooperation and Exchanges
CHINARE (IC201203).
Conflict of interest The authors declare that they have no conflict of
interest.
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