[1] Seasonal and interannual variations of the New Guinea Coastal Current (NGCC) and New Guinea Coastal Undercurrent (NGCUC) were investigated by examining the 5 years' data from acoustic Doppler current profiler moorings at two sites (2°S 142°E, 2.5°S 142°E) off the New Guinea coast. The NGCC flowed northwestward as is usual and intensified during the boreal summer, then weakened or even reversed direction to southeastward during the boreal winter. This seasonal change correlated to the monsoonal wind variation. However, during the 1997-1998 El Niño, the southeastward NGCC during the boreal winter was not observed, and northwestward flow was dominant throughout the year. On the other hand, the NGCUC flowed steadily northwestward all year-round and intensified during the boreal summer. During the growing phase of the El Niño, the NGCUC intensified, and its northwestward flow reached from the surface to a depth of 250 m. Comparison between the volume transport of these currents and the Sverdrup transport along 2°S in the ocean interior indicated a mean difference of 13 Â 10 6 m 3 s À1 northward. The relationship between variations of these two transports showed a negative correlation on seasonal timescales except during the El Niño. During the mature phase of the El Niño, northward Sverdrup transport was enhanced significantly, furthermore the transport of these currents was also northward. The result demonstrates a process by which anomalous water volumes can flow into the equatorial region due to an imbalance between the volume transport in the ocean interior and the western boundary.

Turbulent and radiative exchanges of heat between the ocean and atmosphere (hereafter heat fluxes), ocean surface wind stress, and state variables used to estimate them, are Essential Ocean Variables (EOVs) and Essential Climate Variables (ECVs) influencing weather and climate. This paper describes an observational strategy for producing 3-hourly, 25-km (and an aspirational goal of hourly at 10-km) heat flux and wind stress fields over the global, ice-free ocean with breakthrough 1-day random uncertainty of 15 W m −2 and a bias of less than 5 W m −2. At present this accuracy target is met only for OceanSITES reference station moorings and research vessels (RVs) that follow best practices. To meet these targets globally, in the next decade, satellite-based observations must be optimized for boundary layer measurements of air temperature, humidity, sea surface temperature, and ocean wind stress. In order to tune and validate these satellite measurements, a complementary global in situ flux array, built around an expanded OceanSITES network of time series reference station moorings, is also needed. The array would include 500-1000 measurement platforms, including autonomous surface vehicles, moored and drifting buoys, RVs, the existing OceanSITES network of 22 flux sites, and new OceanSITES expanded in 19 key regions. This array would be globally distributed, with 1-3 measurement platforms in each nominal 10 • by 10 • box. These improved moisture and temperature profiles and surface data, if assimilated into Numerical Weather Prediction (NWP) models, would lead to better representation of cloud formation processes, improving state variables and surface radiative and turbulent fluxes from these models. The in situ flux array provides globally distributed measurements and metrics for satellite algorithm development,

Details of subsurface ocean conditions associated with the Indian Ocean Dipole event (IOD) were observed for the first time by mooring buoys in the eastern equatorial Indian Ocean. Large‐scale sea surface signals in the tropical Indian Ocean associated with the positive IOD started in August 2006, and the anomalous conditions continued until December 2006. Data from the mooring buoys, however, captured the first appearance of the negative temperature anomaly at the thermocline depth with strong westward current anomalies in May 2006, about three months earlier than the development of the surface signatures. These subsurface evolutions within the ocean would be a key factor for better understanding of IOD mechanisms and its predictability, and are providing a fundamental dataset for validation of modeling outputs.

Satellite observations show that large‐scale phytoplankton blooms (increases in chlorophyll) occurred in the equatorial Pacific in 1998, 2003, and 2005, following termination of the three most recent El Niño events. The occurrence of blooms following successive El Niño events cannot be explained by local enhancement of vertical nutrient flux, as evidenced by observations of equatorial winds, thermocline depth, and the depth and strength of the Equatorial Undercurrent (EUC, which supplies the limiting nutrient iron to the euphotic zone). However, near the peak of each El Niño event (late in 1997, 2002, and 2004), while the thermocline of the western equatorial Pacific was anomalously shallow, the flow of the New Guinea Coastal Undercurrent (NGCUC, which is the primary source of iron‐enriched waters to the EUC) intensified, and its core shoaled from >200 m to ∼100 m depth. Analysis of NGCUC variability using a high‐resolution, terrain‐following three‐dimensional ocean circulation model simulation indicates that as the NGCUC shoals and intensifies, it develops meanders and eddies that augment coupling of the New Guinea shelf and upper slope to the EUC. We hypothesize that these changes in NGCUC circulation during El Niño enhance iron transport from the New Guinea margin into the EUC and thereby trigger large‐scale blooms when iron‐enriched waters subsequently reach the euphotic zone along the equator. The threefold to fourfold chlorophyll increases over large regions, up to ∼5 × 105 km2, must have profound impacts on the equatorial ecosystem and biogeochemical cycles.

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