Abstract
Under the influence of recent global warming, modulation of frequencies and amplitude of El Niño-Southern Oscillation (ENSO) and its impacts on global climate have become great concerns to the global community. Antarctic climate is sensitive to these changes owing to tropical and Southern Hemispheric (SH) teleconnections. Antarctic surface air temperature (SAT) reconstructed approximately for the past five centuries (~1533 to 1993 CE) based on multiple oxygen isotope (δ18O) records of ice cores from East and West Antarctica show dominant oscillations in ENSO and Pacific Decadal Oscillation (PDO) frequency bands. Further, variance of the East Antarctica (EA) temperature record shows significant increasing trend at ENSO band and decreasing trend at PDO band since the industrial era (~1850 CE). This observation is consistent with the earlier report of increasing ENSO activity, reconstructed based on tropical-subtropical tree ring records. ENSO influence in the SH high-latitude is known to be characterized by Pacific South American (PSA) pattern reflected in the atmospheric pressure fields. Our investigation of greenhouse gas (GHG) forced model simulation results show an increasing trend in PSA activity since the industrial era. Thus, we suggest ENSO activity and its influence on Antarctic temperature are increasing in response to increasing radiative GHG forcing since the industrial era.
Highlights
To reconstruct past El NiñoSouthern Oscillation (ENSO) behavior and predict its future trend, several attempts have been made based on model simulations and proxy records
We used oxygen isotope (δ18O) records of ice cores from East and West Antarctica (Fig. 1a, Table S1, and reference therein) that are freely available[16]. These ice core records were chosen based on two criteria; (i) sufficiently longer records with a resolution of minimum one year and (ii) locations of these cores should come under the influence of ENSO and Pacific Decadal Oscillation (PDO)
We found four such records of δ18O from East and West Antarctica that are suitable for this purpose (Fig. 1a)
Summary
To reconstruct past ENSO behavior and predict its future trend, several attempts have been made based on model simulations and proxy records. We have reconstructed Antarctic surface air temperature (SAT) for the last five centuries from East and West Antarctica ice core records and investigated temperature signals in ENSO and PDO bands to examine long-term variability in their influence on Antarctic SAT.
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