Enhanced Warming and Intensification of the Kuroshio Extension, 1999–2013

You-Lin Wang,Chau-Ron Wu

doi:10.3390/rs11010101

Abstract

The Pacific climate regime has anomalous warm and cool periods every decade associated with atmospheric circulation changes, which are known to have modulated the tropical and subtropical Pacific during the recent Pacific hiatus regime (1999–2013). However, the influence of the hiatus regime on the Kuroshio Extension (KE) remains unclear. Here, we show that the KE jet underwent enhanced warming (increased 1–1.5 °C), intensification (8–19%) and northward migration (0.5–1°). The KE jet became more perturbed in the upstream region (increased by 70%, west of 146°E) but became stable downstream (perturbation decreased 5–11%, east of 146°E). A poleward shift of the mid-latitude jet stream and weakened Aleutian Low (AL) contributed to the northward migration and intensification of the KE jet, respectively. The weakened AL was associated with negative wind stress curl (WSC) in the eastern Pacific, and this WSC generated an underlying positive sea surface height anomaly that propagated westward, intensifying the KE jet when it reached the KE region. Since the recent Pacific hiatus regime ended after 2013, these changes of the KE jet may reverse during the ongoing warming regime.

Highlights

As ocean circulation is mainly driven by surface winds, the Pacific trade winds and westerlies are vitally important to modulating the North Pacific subtropical gyre (Figure 1a)
The seasea surface temperature (SST) warmed by 1 ◦ C over the north flank of the Kuroshio Extension (KE) jet during the recent Pacific cold regime (Figure 3a), while the KE jet’s first quasi-stationary meanders (141◦ E–146◦ E) [59] simultaneously of 13 −1 intensified, reaching 10–40 cm s−1 in its north flank (Figure 3b), which decreased to 10–305 cm s in the south flank
The amplitude of the intensified north flank is greater than that of the south flank, intensified, reaching 10–40 cm s−1 in its north flank (Figure 3b), which decreased to 10–30 cm s−1 in the indicating an intensified jet, and the meridional variation in speed may be due to northward south flank

Summary

Introduction

As ocean circulation is mainly driven by surface winds, the Pacific trade winds and westerlies are vitally important to modulating the North Pacific subtropical gyre (Figure 1a). The Kuroshio flows eastward as the Kuroshio Extension (KE) off Japan into the mid-latitudes of the Pacific, and releases large amounts of heat and moisture into the atmosphere (Figure 1b) [16,17,18,19]. These strong ocean-to-atmosphere fluxes modulate the mean atmospheric state, feed storms, and anchor storm tracks [17,20,21,22,23]. Oceanic heat in the KE region is influenced by this process, as evidenced by the slow westward propagation of oceanic mesoscale eddies and variability of the KE jet [25,26,27]

Methods

Results

Discussion

Conclusion