In the eastern equatorial pacific wang and mcphaden

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In the eastern equatorial Pacific Wang and McPhaden (2001) found that the strong El Niños of 1982-3 and 1997 were associated with mixed layer deepening of 30m or more at 0 o N, 110 o W ( Cronin and Kessler, 2002 also examine the 1997 event). The decrease in entrainment associated with the deepening mixed layer and weakening of the upwelling was found to be an important term in the mixed layer heat budget at this location. In Fig. 12a we determine a similar relationship for oceanic variables averaged over the NIÑO3 region (150 o W-90 o W, 5 o S-5 o N). 14
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Averaged annually to improve the statistics the vertical excursions of MLD reduce to a more modest 10m. However, there remains a similarly close relationship between deepening thermocline and increasing SST with a ratio of 0.1 o C/m, as well as a close relationship to variations in the zonal wind speed in the west ( Fig. 12c ). In the western equatorial Pacific we find, similar to Wang and Mcphaden , that substantial variations in MLD are evident ( Fig. 12b ), which lag variations in surface winds by several months ( Fig.12c ). The MLD variations in the West Pacific are not closely related to variations in West Pacific SST ( Fig. 12b ). The extension of the ENSO response into the eastern Indian Ocean ( Fig. 10 ) is also evident in our examination of the primary EOF of MLD during December-February ( Fig. 13 ). The spatial pattern of the mixed layer response associated with this EOF, which explains 9.5% of the record variance, has a maximum in the eastern tropics. The pattern extends further south along the Sumatra coast, with a minimum south of the equator in the central basin. The corresponding principal component time series shows that this pattern is closely related to the SOI so that MLD along the equator in the east is shallow during El Niños. Interannaual variations of the mixed layer during boreal winter seem to be connected to the local wind response to ENSO. MLD variations are confined primarily to the eastern and central basin and reflect changes of the equatorial and coastal upwelling in the east and the pattern of Ekman pumping produced by the cyclonic winds in the south central basin ( Fig. 13a ) (see also Murtugudde et al. , 1999; Potemra and Lukas , 1999; and Grodsky et al ., 2001). In contrast to the situation in December-February, the primary EOF during the peak season of the Southwest Monsoon in boreal summer reveals the MLD variability confined to the western basin 15
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( Fig. 14 ). During this season variations in MLD are associated with changes in the strength of the monsoonal winds, as suggested in recent studies by Prasad (2004) and Babu et al. (2004) . 6. Summary and Discussion In this work we apply the methodology of de Boyer Montegut et al . (2004) to construct a monthly analysis of global mixed layer depth (MLD) during the 45-year period 1960-2004 based on profiles from the new WOD05 data set. The data set is limited in temporal and geographic coverage, and thus averaging is required to identify year-to-year variability. The problem of limited data is magnified since much of the MLD variability is linked to the seasonal cycle.
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  • Spring '17
  • william james
  • The Land, Atlantic Ocean, Pacific Ocean, North Pacific Ocean, North Pacific, mixed layer

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