Students Research Presentations: Comparing paleoclimate reconstructions of the North Atlantic Oscillation: finding the signal in the noise

Year:

2022

Source:

Ocean Sciences Meeting, Virtual

Abstract:

The North Atlantic Oscillation (NAO) is the dominant atmospheric pressure pattern over the northern sector of the Atlantic Ocean. It exerts a strong influence on temperatures, storm tracks, and precipitation patterns in the region. Wind forcing by the NAO has been linked to other climate patterns such as Atlantic Multidecadal Variability (AMV) and the Atlantic Meridional Overturning Circulation. Testing the proposed links between NAO and low-frequency patterns in the climate system, such as AMV, requires records of NAO and temperature that span multiple centuries. Teasing apart natural climate processes from anthropogenic ones requires long records from the pre-anthropogenic era.  The longest instrumental measures of the NAO are from station-based sea level pressure records and extend back to the 1820s, only a few decades before the onset of modern anthropogenic warming. Paleoclimate proxies that are sensitive to the NAO can provide longer records. Several paleoclimate reconstructions of NAO exist, but it is unclear how they compare quantitatively to each other and to instrument-based NAO indices. In this study, we compare different NAO reconstructions with three different instrument-based NAO indices over the same time period and with the same statistical methods to quantitatively compare the reconstructions. Standard comparative statistics are used to quantify the shared variance, reconstruction skill, and residual reconstruction errors. Furthermore, the data is filtered to compare the reconstruction fidelity at low and high frequencies. The results indicated that a few recent reconstructions are clearly better at capturing the instrumental NAO variability, but the best reconstruction often depends on what statistical measure or reconstruction target is used. Thus, different NAO reconstructions may be better for different purposes. The results of this study can be used to inform researchers’ choice of NAO reconstruction to utilize in their own research.
 

Mentors:

Halimeda Kilbourne, Ph.D.

Students:

Jeanne DeMeo, Pitzer College