Sources of low-frequency δ^18O variability in coastal ice cores from Dronning Maud Land
arxiv(2024)
摘要
The low-frequency variability of the δ^18O recorded in ice cores
(FK17 and TIR18) recently drilled at two different locations in Dronning Maud
Land (Antarctica), is investigated using multi-taper spectral method and
singular spectrum analysis. Multiple dominant peaks emerge in these records
with periods between 3 and 20 years. The two sites show distinct spectral
signatures, despite their relative proximity in space (about 100 km apart),
suggesting that different processes are involved in generating the variability
at these two sites. In order to clarify which processes are acting on
δ^18O at these two locations, the impact of several climate indices as
well as sea ice area is investigated using a causal method, known as the
Liang-Kleeman rate of information transfer. The analysis of the origin of this
low-frequency variability from external sources reveals that El Niño-Southern
Oscillation (ENSO), the Pacific Decadal Oscillation (PDO), the Southern Annular
Mode (SAM), the Dipole Mode Index (DMI) and the sea ice area display important
causal influences on δ^18O at FK17. For TIR18, the main influences are
from ENSO, PDO, DMI, the sea ice area, and the Atlantic Multidecadal
Oscillation (AMO), revealing the complexity of the interactions in Dronning
Maud Land. The two locations share several drivers, but also show local
specificities potentially linked to ocean proximity and differences in air mass
trajectories. The implication of these findings on the low-frequency
variability in the two ice cores is discussed.
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