Decadal Ocean/Atmosphere Variability in the North Pacific in CCSM2 (Model Years 350-999)

Decadal Ocean/Atmosphere Variability in the North Pacific in CCSM2(Model Years 350-999) Young-Oh Kwon and Clara Deser NCAR 9th Annual CCSM Workshop (July 7-9 2004, Santa Fe, NM)

EOF 1 (22 %) Winter SST Anomalies CCSM2

Winter SST Kuroshio Extension Index

80 25 10 Power Spectrum Winter SST Kuroshio Extension Index ~40 yr ~16 yr

SST Local Qnet SST Local Precipitation Qnet and Precipitation in the Kuroshio Extension

Correlation between Winter SST KEIand Indices at Other Depths Band Pass Filtered : 10 – 25 yrs Band-Pass Filtered : 25 – 80 yrs Shaded areas are significant at 95 % C.L. Contour interval : 0.1

Correlation between Winter SST KEI and Temperature on the Section along 40 °N Band Pass Filtered : 10 – 25 yrs Contour interval : 0.1 Shaded areas are significant at 95 % C.L.

Winter Temperature Anomaly at 500 m Contour interval : 0.2 °C

SST, Qnet and Precipitation along 40 °N Contour intervals : 0.5 °C, 20 W/m2, 0.5 mm/day

SST Kuroshio Position ~30 yr Winter SST KEI and Position of the Kuroshio

SST ~40 yr Winter SST KEI and Kuroshio Transport Kuroshio Transport

~20 yr Observed Winter SST in Kuroshio Extension (Reynolds SST : 1901-2000)

Observed Winter SST Anomaly along 40 °N Band Pass Filtered : 7 – 15 yrs Band-Pass Filtered : 15 – 25 yrs Contour interval : 0.2 °C

Summary • Robust decadal (~16 years) and interdecadal (~40 years) variability in Kuroshio Extension. • SST, precipitation, surface heat flux, and subsurface temperature. • Ocean dynamics likely play an active role. • Anomaly penetrating down to 1000 m. • Propagating with the Kuroshio Extension. • Heat flux and precipitation responding to SST anomaly. • Anomalous Ekman heat transport acts as a positive feedback response to the SST anomalies. • Similar spectral peaks in Kuroshio transport and position. • Weak atmospheric response. • Some resemblance to Nature.

Decadal Ocean/Atmosphere Variability in the North Pacific in CCSM2 (Model Years 350-999)