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| Titel |
Coeval dust accumulation minima in Greenland and East Central Europe over
31-23 ka |
| VerfasserIn |
Gábor Újvári, Thomas Stevens, György Varga, János Kovács, Mihály Molnár |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250123522
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| Publikation (Nr.) |
 EGU/EGU2016-2794.pdf |
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| Zusammenfassung |
| As reflected in δ18O values in ice cores, the North Atlantic area experienced a series of
abrupt, dramatic climatic fluctuations over the last glacial during which oceanic and
atmospheric conditions alternated between full glacial (stadial) and relatively mild
(interstadial) conditions [1,2]. Beyond the δ18O profiles, calcium ion concentration data
(hereafter [Ca2+]) also exhibit particularly clear stadial/interstadial contrasts [3].
The Ca2+/dust concentration records are considered as a proxy for the amount
of terrestrial dust reaching the ice sheet [4] and/or changing dust storm activity
in the source areas around the Northern Hemisphere, mainly in East Asia [5,6].
The mode of the dust size distributions is thought to reflect transit times during
transport, with larger modes indicating shorter transit times and transport routes, i.e.
changed atmospheric circulation patterns [5]. However, based on clay mineralogy and
Sr-Nd isotopic compositions of loess sediments Újvári, et al. [7] suggested that
Central European dust cannot be excluded as a potential source of Greenland dust. As
such, it is vital to analyze dust deposition in the key dust depocentres of Eastern
Europe.
As a record of Carpathian Basin dust source activity, we therefore studied loess
sedimentation and grain size changes in the Dunaszekcső loess sequence in Southern
Hungary. For this record, we developed the highest resolution geochronological dataset for
European loess based on 61 AMS 14C dates from molluscs and charcoal fragments. This
allowed us to establish a uniquely high precision Bayesian age-depth model, with the
mean 95% confidence ranges that vary between 119 and 798 yr. Sedimentation rates
(SR) calculated from the age-depth model vary between 0.36-1.7 mm yr−1 and the
estimated bulk dust mass accumulation rates (MAR) range from 551 to 2525 g m−2
yr−1. Both the SR and MAR display millennial/sub-millennial scale variations,
visible uniquely due to the high precision dating, together with the bulk loess median
grain size (D50bulk) that is considered an integrated proxy of wind strength, dust
source distance, aridity and vegetation cover. While an increase of dust flux and
D50bulk with time is apparent, such a trend cannot be seen in the quartz grain size
measures (D50quartz). This observation may imply that wind speeds were relatively
constant in the studied time interval, while the turbulence of the flow may have been
extremely varying (i.e. strong/rapid changes in the frequency/magnitude of dust storm
events).
A striking feature of the MAR record is that accumulation minima in the Dunaszekcső
record are synchronous with the Greenland Interstadials (GI-5.1 to GI-3). Subsequent Ca2+
minima in the NGRIP record at 26.22 and 25.02 ka (b2k) are also coeval with the MAR
minima in the studied loess sequence. At the same time, these patterns are barely visible in
the bulk and quartz grain size records. We speculate that the synchronous changes in the
NGRIP Ca2+ and the Dunaszekcső MAR records are results of millennial scale variations in
the activity of Northern Hemisphere dust emitting regions shown in two archives from
different environments. The very similar timing of MAR minima (and also some of
the maxima) suggest a rapid aeolian system response in East Central Europe to
abrupt climatic changes in the North Atlantic. Although such a synchronicity does
not prove a Central European dust source to Greenland, it is consistent with this
possibility.
This study was supported by the OTKA PD-108639 grant and the Bolyai János Research
Fellowship (both to GÚ).
[1] Dansgaard, W., et al. (1993). Evidence for general instability of past climate from a
250-kyr ice-core record. Nature 364, 218-220.
[2] Johnsen, S.J., et al. (1992). Irregular glacial interstadials recorded in a new Greenland
ice core. Nature 359, 311-313.
[3] Rasmussen, S.O., et al. (2014). A stratigraphic framework for abrupt climatic changes
during the Last Glacial period based on three synchronized Greenland ice-core records:
refining and extending the INTIMATE event stratigraphy. Quaternary Science Reviews 106,
14-28.
[4] Fuhrer, K. et al. (1999). Timescales for dust variability in the Greenland Ice Core
Project (GRIP) ice core in the last 100,000 years. Journal of Geophysical Research 104,
31,043-31,052.
[5] Ruth, U., et al. (2003). Continuous record of microparticle concentration and size
distribution in the central Greenland NGRIP ice core during the last glacial period. Journal of
Geophysical Research 108, 4098.
[6] Ruth, U., et al. (2007). Ice core evidence for a very tight link between North Atlantic
and east Asian glacial climate. Geophysical Research Letters 34, L03706.
[7] Újvári, G., et al. (2015). Two possible source regions for central Greenland last glacial
dust. Geophysical Research Letters 42, 10,399-10,408. |
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