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

Power Spectrum Winter SST Kuroshio Extension Index

~16 yr~40 yr

102580

Qnet and Precipitation in the Kuroshio Extension

SST

Local Qnet

SST

Local Precipitation

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

Shaded areas are significant at 95 % C.L.Contour interval : 0.1

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

Winter SST KEI and Position of the Kuroshio SST

Kuroshio Position

~30 yr

Winter SST KEI and Kuroshio TransportSST

Kuroshio Transport

~40 yr

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

~20 yr

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.