Contrasting Decadal and Inter-decadal Components of ENSO-like Variability in the Pacific
Abstract
In this study we present evidence that the ENSO-like variability in the Pacific basin has a distinct decadal (7-20 years) component which is distinguished from the inter-decadal (>20 years) component. The ENSO-like decadal variability is comprised of central tropical Pacific sea surface temperature (SST) variations and meridional sea level pressure dipole structures in both the extratropical North and South Pacific, with the northern part resembling the North Pacific Oscillation (NPO). In contrast, the inter-decadal component, or equivalently the Inter-decadal Pacific Oscillation (IPO), features SST anomalies in the subtropical eastern Pacific and Aleutian Low intensity variations in the North Pacific. The North Pacific Gyre Oscillation (NPGO) and Pacific Decadal Oscillation (PDO) are sub-basin expressions of the basin-wide ENSO-like variability on decadal and inter-decadal timescales, respectively.
Separating decadal and inter-decadal variability is necessary to better understand the observed climate variations and changes as well as to identify different mechanisms, climate impacts, potential predictability, and inter-basin connections on these timescales. Taking sea level as an example, the relatively short satellite altimeter observations available after 1993 sample about two decadal cycles that are closely related to the ENSO-like decadal variability. Meanwhile, longer (~60 years) sea level datasets not only record decadal cycles but also show the regional sea level trend reversal before and after the early 1990s due to the ENSO-like inter-decadal variability which contributes to the observed regional sea level trends over the altimeter period. The sea level evolution on decadal timescale indicates ocean Rossby wave propagation mainly along the mid-latitude and subtropical North Pacific bands, which are key processes connecting the tropics and extra-tropics through the subtropical cell and determining the timescale and predictability of this decadal variability. We also find coherent decadal sea level variations across the Indo-Pacific basin linked via the Indonesian Throughflow and the co-varying Indian and Pacific Walker Circulation.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFMGC31F1238L
- Keywords:
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- 3339 Ocean/atmosphere interactions;
- ATMOSPHERIC PROCESSES;
- 1616 Climate variability;
- GLOBAL CHANGE;
- 1620 Climate dynamics;
- GLOBAL CHANGE;
- 4513 Decadal ocean variability;
- OCEANOGRAPHY: PHYSICAL