 |
| Titel |
Reconstructing the past climate variability in Svalbard from the Lomonosovfonna and Holtedahlfonna δ¹⁸O ice core records |
| VerfasserIn |
Dmitry Divine, Elisabeth Isaksson, Tonu Martma, Vejio Pohjola, Harro Meijer, Roderik S. W. van de Wal, John Moore, Fred Godtliebsen |
| Konferenz |
EGU General Assembly 2010
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250033704
|
|
|
|
|
|
| Zusammenfassung |
| We examine the isotopic records (δ18O) from two ice cores drilled on small Arctic ice caps in
Svalbard in 1997 and 2005 for their potential as proxies for past surface air temperatures
(SAT) on Svalbard. The isotope concentrations in the snow pack are considered to be a proxy
for condensation temperatures at the time of precipitation at the core. They can
subsequently be associated with past local SAT variations. The core sites are located at
Lomonosovfonna at 1250 m asl and Holtedahlfonna at 1150 m asl. The analyzed isotopic
time-series are estimated to cover the periods of AD 1130-1997 and AD 1700-2005,
respectively. The analysis of δ18O series against the instrumental temperature record from
Longyearbyen on Svalbard (regular data available since 1912) and longer but more
remote Vardø series from northern Norway (since 1840) suggests that δ18O can
successfully be used as a proxy for winter SAT on Svalbard. The residuals of the
difference between the two annual mean δ18O series are randomly distributed. It
suggests similar processes to drive the variability in precipitation seasonality and
δ18O and indicates that stacking (standardization and averaging) of these records
can reduce the non-climatic noise variance in the resulted series. We then applied
scaling approach to reconstruct the winter temperature variability in Longyearbyen
(Svalbard) and Vardø (Northern Norway). All reconstructions suggest the culmination
of the Little Ice Age - associated cooling in the second half of the 18th century
and abrupt warming in the beginning of the 20th century. The coldest period in
Longyearbyen and Vardø during the 1800s is characterized by winter cooling of
the order of 5 and 2 oC, on average, respectively. The records show, however, that
some few year-long sporadic events of increased winter SAT, as high as up to the
modern levels could also have place even during the LIA. Analysis of the longer
Lomonosovfonna record alone suggests a relatively smooth climate transition from
the Medieval Climate Optimum to the LIA, making it difficult to associate one
with any specific time interval. The inferred winter SAT during the 1100s are even
higher than the winter SAT which were observed on Svalbard in the end of the
1990s. Ionic washout indices indicative of the intensity of summer melting, in turn,
indirectly confirms that summers on Svalbard in the 1100s might be as warm as
during the last decade. It suggests that the climate conditions on Svalbard during the
Medieval Warm Period were quite similar to those observed at the present time. |
|
|
|
|
|
|