GFDL Informal Seminar

Tue, Feb 25, 2020, 10:30 am to 11:30 am

Pacific climate and weather extremes including heatwaves, drought, and hydrological hazard, which drive significant impact on the U.S. community and thus have been paid great attention, are dynamically linked to not only local air-sea interactions, but also large-scale climate variability (e.g., Pacific decadal variability and El Niño Southern Oscillation). This study aims at improving the theories of climate coupling within the North Pacific and across to the central tropical Pacific with investigating their response to anthropogenic forcing. Using multiple observational reanalyses and global climate model ensembles, we first show that winter ocean temperature extremes over the Northeast Pacific significantly resemble the representations of the North Pacific decadal variability (e.g., North Pacific Gyre Oscillation, NPGO and Pacific Decadal Oscillation, PDO). We find that the multi-year warm anomalies in the Northeast Pacific are associated with the consecutive occurrences of NPGO-like and PDO-like ocean signatures via ENSO atmospheric teleconnections. The results suggest that the increasing coupling between NPGO and PDO leads to the prolonged North Pacific marine heatwaves, and those warm events are becoming stronger in amplitude with a larger area under anthropogenic forcing. Combining satellite data with several observation reanalysis products, we next offer observational evidence revealing that a preferred decadal timescale (~10yrs) in the North Pacific western boundary current system, the Kuroshio Extension (KE) region, may arise from an interaction with the central tropical Pacific (CP) (e.g., CP-ENSO). The results show that the KE decadal dynamic state can drive a persistent downstream wind stress curl that projects on atmospheric forcing of the CP-ENSO, which in turn excites westward oceanic Rossby waves in the central North Pacific that reach the western boundary back. Consistent with this hypothesis, the cross-correlation function between the KE and CP-ENSO indices exhibits a significant sinusoidal shape corresponding to a preferred spectral power at 10yrs. Using high-resolution coupled climate models, we finally show that the decadal KE dynamics are not independent of the central tropics and their coupling is becoming stronger under anthropogenic forcing. The results suggest that a higher amplitude quasi-decadal KE/CP-ENSO sequence under warmer climate may allow a stronger basis for decadal predictions of Pacific climate variability, further for societally relevant biogeochemical quantities (e.g., salinity, oxygen, and chlorophyll-A) and fisheries.

Location: 
Smagorinsky Seminar Room 209
Speaker(s): 

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Location: Smagorinsky Seminar Room 209

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Location: Maeder Hall, 92 Olden Street, Princeton, N.J. 08540

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Thu, Apr 9, 2020, 2:00 pm to 3:00 pm
Location: Smagorinsky Seminar Room 209

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Location: Guyot 220

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Location: Zoom

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[Virtual] GEO Department Lecture via Zoom

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Location: Sayre Hall Conference Room