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| Titel |
Causes of Greenland temperature variability over the past 4000 yr: implications for northern hemispheric temperature changes |
| VerfasserIn |
T. Kobashi, K. Goto-Azuma, J. E. Box, C.-C. Gao, T. Nakaegawa |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1814-9324
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| Digitales Dokument |
URL |
| Erschienen |
In: Climate of the Past ; 9, no. 5 ; Nr. 9, no. 5 (2013-10-15), S.2299-2317 |
| Datensatznummer |
250085231
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| Publikation (Nr.) |
 copernicus.org/cp-9-2299-2013.pdf |
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| Zusammenfassung |
| Precise understanding of Greenland temperature variability is important
in two ways. First, Greenland ice sheet melting associated with rising
temperature is a major global sea level forcing, potentially affecting large
populations in coming centuries. Second, Greenland temperatures are highly
affected by North Atlantic Oscillation/Arctic Oscillation (NAO/AO) and
Atlantic multidecadal oscillation (AMO). In our earlier study, we found
that Greenland temperature deviated negatively (positively) from northern
hemispheric (NH) temperature trend during stronger (weaker) solar activity
owing to changes in atmospheric/oceanic changes (e.g. NAO/AO) over the
past 800 yr (Kobashi et al., 2013). Therefore, a precise
Greenland temperature record can provide important constraints on the past
atmospheric/oceanic circulation in the region and beyond. Here, we
investigated Greenland temperature variability over the past 4000 yr
reconstructed from argon and nitrogen isotopes from trapped air in a GISP2
ice core, using a one-dimensional energy balance model with orbital, solar,
volcanic, greenhouse gas, and aerosol forcings. The modelled northern
Northern Hemisphere (NH) temperature exhibits a cooling trend over the past 4000 yr
as observed for the reconstructed Greenland temperature through
decreasing annual average insolation. With consideration of the negative
influence of solar variability, the modelled and observed Greenland
temperatures agree with correlation coefficients of r = 0.34–0.36
(p = 0.1–0.04) in 21 yr running means (RMs) and r = 0.38–0.45 (p = 0.1–0.05) on a
centennial timescale (101 yr RMs). Thus, the model can explain 14 to
20% of variance of the observed Greenland temperature in multidecadal to
centennial timescales with a 90–96% confidence interval, suggesting that
a weak but persistent negative solar influence on Greenland temperature
continued over the past 4000 yr. Then, we estimated the distribution of
multidecadal NH and northern high-latitude temperatures over the past 4000 yr
constrained by the climate model and Greenland temperatures. Estimated
northern NH temperature and NH average temperature from the model and the
Greenland temperature agree with published multi-proxy temperature records
with r = 0.35–0.60 in a 92–99% confidence interval over the past 2000 yr.
We found that greenhouse gases played two important roles over the
past 4000 yr for the rapid warming during the 20th century and
slightly cooler temperature during the early period of the past 4000 yr.
Lastly, our analysis indicated that the current average temperature
(1990–2010) or higher temperatures occurred at a frequency of 1.3 times per
1000 yr for northern high latitudes and 0.36 times per 4000 yr for NH
temperatures, respectively, indicating that the current multidecadal NH
temperature (1990–2010) is more likely unprecedented than not (p = 0.36)
for the past 4000 yr. |
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