In this study, the Indian Ocean upper-ocean variability associated with the subtropical Indian Ocean dipole (SIOD) is investigated. We find that the SIOD is associated with a prominent southwest–northeast sea level anomaly (SLA) dipole over the western-central south Indian Ocean, with the north pole located in the Seychelles–Chagos thermocline ridge (SCTR) and the south pole at southeast of Madagascar, which is different from the distribution of the sea surface temperature anomaly (SSTA). While the thermocline depth and upper-ocean heat content anomalies mirror SLAs, the air–sea CO2 flux anomalies associated with SIOD are controlled by SSTA. In the SCTR region, the westward propagation of oceanic Rossby waves generated by anomalous winds over the eastern tropical Indian Ocean is the major cause for the SLAs, with cyclonic wind causing negative SLAs during positive SIOD (pSIOD). Local wind forcing is the primary driver for the SLAs southeast of Madagascar, with anticyclonic winds causing positive SLAs. Since the SIOD is correlated with ENSO, the relative roles of the SIOD and ENSO are examined. We find that while ENSO can induce significant SLAs in the SCTR region through an atmospheric bridge, it has negligible impact on the SLA to the southeast of Madagascar. Bymore »
Ocean warming and accelerating Southern Ocean zonal flow
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In this paper, we outline the need for a coordinated international effort toward the building of an open-access Global Ocean Oxygen Database and ATlas (GO 2 DAT) complying with the FAIR principles (Findable, Accessible, Interoperable, and Reusable). GO 2 DAT will combine data from the coastal and open ocean, as measured by the chemical Winkler titration method or by sensors (e.g., optodes, electrodes) from Eulerian and Lagrangian platforms (e.g., ships, moorings, profiling floats, gliders, ships of opportunities, marine mammals, cabled observatories). GO 2 DAT will further adopt a community-agreed, fully documented metadata format and a consistent quality control (QC) procedure and quality flagging (QF) system. GO 2 DAT will serve to support the development of advanced data analysis and biogeochemical models for improving our mapping, understanding and forecasting capabilities for ocean O 2 changes and deoxygenation trends. It will offer the opportunity to develop quality-controlled data synthesis products with unprecedented spatial (vertical and horizontal) and temporal (sub-seasonal to multi-decadal) resolution. These products will support model assessment, improvement and evaluation as well as the development of climate and ocean health indicators. They will further support the decision-making processes associated with the emerging blue economy, the conservation of marine resources and theirmore »