The annual mean sketches and climatological variability of the volume and heat transports through the inter-basin passages: A study based on 1 400-year spin up of MOM4p1

The annual mean volume and heat transport sketches through the inter-basin passages and transoceanic sections have been constructed based on 1 400-year spin up results of the MOM4p1. The spin up starts from a state of rest, driven by the monthly climatological mean force from the NOAA World Ocean Atlas (1994). The volume transport sketch reveals the northward transport throughout the Pacific and southward transport at all latitudes in the Atlantic. The annual mean strength of the Pacific-Arctic-Atlantic through flow is 0.63×10⁶ m³/s in the Bering Strait. The majority of the northward volume transport in the southern Pacific turns into the Indonesian through flow (ITF) and joins the Indian Ocean equatorial current, which subsequently flows out southward from the Mozambique Channel, with its majority superimposed on the Antarctic Circumpolar Current (ACC). This anti-cyclonic circulation around Australia has a strength of 11×10⁶ m³/s according to the model-produced result. The atmospheric fresh water transport, known as P-E+R (precipitation minus evaporation plus runoff), constructs a complement to the horizontal volume transport of the ocean. The annual mean heat transport sketch exhibits a northward heat transport in the Atlantic and poleward heat transport in the global ocean. The surface heat flux acts as a complement to the horizontal heat transport of the ocean. The climatological volume transports describe the most important features through the inter-basin passages and in the associated basins, including: the positive P-E+R in the Arctic substantially strengthening the East Greenland Current in summer; semiannual variability of the volume transport in the Drake Passage and the southern Atlantic-Indian Ocean passage; and annual transport variability of the ITF intensifying in the boreal summer. The climatological heat transports show heat storage in July and heat deficit in January in the Arctic; heat storage in January and heat deficit in July in the Antarctic circumpolar current regime (ACCR); and intensified heat transport of the ITF in July. The volume transport of the ITF is synchronous with the volume transport through the southern Indo-Pacific sections, but the year-long southward heat transport of the ITF is out of phase with the heat transport through the equatorial Pacific, which is northward before May and southward after May. This clarifies the majority of the ITF originating from the southern Pacific Ocean.