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| Titel |
On trends in Arctic sea-ice motion: spatial distribution, significance, and the role of the ocean |
| VerfasserIn |
Torge Martin, Rüdiger Gerdes, Frank Kauker |
| Konferenz |
EGU General Assembly 2011
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250048525
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| Zusammenfassung |
| The dramatic changes of the Arctic Ocean’s sea-ice cover extent have drawn major scientific
and public attention during the past decade. The strong decrease of the ice extent is viewed as
an important indicator for (global) climate warming. In more recent years it has been shown
from observations and various model simulations that the areal reduction of sea ice is
accompanied by a negative trend in ice thickness. However, the third basic quantity
describing the Arctic pack ice, its motion, has not yet been studied in detail with respect to
eventual long-term changes. Understanding and estimating the (relative) motion of
the ice pack correctly is essential in order to correctly predict the future evolution
of the sea-ice cover. Accelerated sea-ice drift may increase ice export, intensify
deformation of the ice cover, and enhance heat exchange between ocean and atmosphere.
Indications for an overall positive trend of the Arctic’s sea-ice drift speed have
been published based on Arctic-wide composites of drift stations and buoy position
measurements (e.g. Hakkinen et al., 2008, GRL; Rampal et al., 2009, JGR). However,
the acceleration is attributed to different reasons, for instance, increased surface
wind stresses over the Arctic (Hakkinen et al., 2008, GRL) and a weakening of the
internal forces of the ice cover due to increased fracturing (Rampal et al., 2009,
JGR).
We study the spatial distribution of trends in sea-ice drift speed using several data sources
including various regional ice-ocean model simulations as well as observational records such
as drifting buoys and satellite derived ice drift. By applying these many different, independent
data sources, which all cover a time period of at least 30 years, we are able to give an estimate
of the significance and robustness of the individual trends. Our findings include that there is
no homogeneous long-term trend for the entire Arctic Ocean neither in magnitude nor
in sign. Averaged over the Arctic Ocean for the past 50 years the overall trend is
small at 0.1-
10-3Â m/s/yr. Strongest, statistically significant changes exceeding
0.5-
10-3Â m/s/yr are found for the regions of the Beaufort Gyre and the Transpolar
Drift Stream including the Fram Strait throughflow. Simulated trends for the period
1979-2007 compare well with observed values. The positive trend in the Beaufort
Sea increases greatly during the past two decades and exceeds 2-
10-3Â m/s/yr. In
contrast, a negative trend of -0.5-
10-3Â m/s/yr is found in the vicinity of the Laptev
Sea.
Further results include an estimate of the influence of a long-term trend in ice thickness
on the ice motion, which we gained by analysing an ice-ocean model experiment that covers
the entire 20th century. And finally, by considering different ice-ocean models and free drift
estimates, we can show that the Arctic’s ocean circulation has major influence on the sea-ice
motion and its trends. |
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