Sources of low-frequency $\delta^{18}$O variability in coastal ice cores from Dronning Maud Land

TL;DR

This study investigates the low-frequency variability of δ18O in Antarctic ice cores from Dronning Maud Land, revealing distinct spectral signatures and multiple climate drivers influencing the isotopic records at two nearby sites.

Contribution

It identifies the different climate processes affecting δ18O variability at two ice core sites and demonstrates the complex interactions between external climate indices and local isotopic signals.

Findings

Multiple spectral peaks between 3 and 20 years in δ18O records.

Distinct spectral signatures at the two sites despite proximity.

ENSO, PDO, DMI, sea ice area, and other indices influence δ18O variability.

Abstract

The low-frequency variability of the $\delta^{18}$O 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 $\delta^{18}$O 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 Ni\~no-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 $\delta^{18}$O 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.