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| Titel |
High resolution water stable isotope profiles of abrupt climate transitions in Greenland ice with new observations from NEEM |
| VerfasserIn |
T. J. Popp, J. W. C. White, V. Gkinis, B. M. Vinther, S. J. Johnsen |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250066284
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| Zusammenfassung |
| In 1989 Willi Dansgaard and others, using the DYE3 ice core, showed that the abrupt
termination of the Younger Dryas expressed in water stable isotope ratios and deuterium
excess was completed in less than 50 years. A few years later, using the GISP2 ice core,
Richard Alley and others proposed that snow accumulation at the site doubled in as little
as 1-3 years across the same climate transition at the end of the Younger Dryas.
Over the next two decades, in large part due to such observations from Greenland
ice cores, a paradigm of linked, abrupt changes in the North Atlantic region has
been developed around North Atlantic deep water formation, North Atlantic sea ice
extent, and widespread atmospheric circulation changes occurring repeatedly during
the last glacial period in response to changing freshwater fluxes to the region, or
perhaps other causes. More recently, with the NGRIP ice core, using a suite of
high resolution proxy data, and in particular deuterium excess, it was observed
again that certain features in the climate system can switch modes from one year
to the next, while other proxies can take from decades to centuries to completely
switch modes. Thus, an event seen in the proxy records such as the abrupt end of the
Younger Dryas (or other interstadial events) may comprise multiple climatic or
oceanic responses with different relative timing and duration which potentially
follow a predictable sequence of events, in some cases separated by only a few
years.
Today, the search continues for these emerging patterns through isotopic and other
highly resolvable proxy data series from ice cores. With the recent completion of
the drilling at NEEM, many abrupt transitions have now been measured in detail
over a geographic transect with drilling sites spanning from DYE3 in Southern
Greenland, GISP2 in the central summit region, and up to NGRIP and NEEM in the far
north. The anatomy of abrupt climate transitions can therefore be examined both
spatially and temporally, where obtaining the highest possible temporal resolution is
desirable to resolve patterns. A new method for measuring water stable isotope
ratios has been developed during the NEEM project that allows us to measure a
carefully controlled fraction of a continuously melted ice core section which is
evaporated directly into Cavity Ring Down Laser Spectrometer in the Near-Infrared
spectrum. In such a system the resolution can be maximized (and characterized)
largely as a function of both the melt rate and minimizing subsequent mixing in
the gas phase during analysis. These new detailed water isotope series from the
NEEM ice core are examined with respect to the corresponding series from new and
previously available series from the other ice cores. The emerging picture indicates
that abrupt climate changes have both a temporal and geographic anatomy that
can change from one event to the next in how they are recorded across Greenland.
Together with modeling and chemical impurity data, these patterns we detect in
the water stable isotope series will provide clues and constraints to the timing and
origin of oceanic and atmospheric changes that make up an abrupt climate change. |
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