Ocean Heat Uptake and Interbasin Transport of the Passive and Redistributive Components of Surface Heating

Abstract

Global warming induces ocean circulation changes that not only can redistribute ocean reservoir temperature stratification but also change the total heat content anomaly of the ocean. Here all consequences of this process are referred to collectively as “redistribution.” Previous model studies of redistributive effects could not measure the net global contribution to the amount of ocean heat uptake by redistribution. In this study, a global ocean model experiment with abrupt increase in surface temperature is conducted with a new passive tracer formulation. This separates ocean heat uptake into contributions due to redistribution temperature and surface heat flux anomalies and those due to the passive advection and mixing of surface heat flux anomalies forced in the atmosphere. For a decline in the Atlantic meridional overturning circulation of about 40%, redistribution nearly doubles the Atlantic passive anomalous surface heat input and depth penetration of temperature anomalies. However, smaller increases in the Indian and Pacific Oceans cause the net global redistributive contribution to be only 25% of the passive contribution. Despite the much larger anomalous surface heat input in the Atlantic, the Pacific gains heat content anomaly similar to that in the Atlantic because of export from the Atlantic and Indian Oceans via the global conveyor belt. Of this interbasin heat transport, most of the passive component comes from the Indian Ocean and the redistributive component comes from the Atlantic.

Deciphering Patterns and Drivers of Heat and Carbon Storage in the Southern Ocean

“…In the climate simulation, enhanced surface buoyancy gain occurs due to a warmer atmosphere driving a larger amount of heat flux into the ocean (Figure 4). Rather, this region coincides with the depth-integrated Q′ storage maxima, which reduces the air-sea temperature difference and provides a negative feedback on the heat flux, as suggested in previous model studies (Armour et al, 2016;Garuba & Klinger, 2016, 2018. Further north, anomalous buoyancy gain occurs at 35-40°S over the southward subduction limb of the shallow subtropical cell, and a large decrease in the southward transport at the surface is also required (ΔΨ res > 0).…”

The Flux-Anomaly-Forced Model Intercomparison Project (FAFMIP) contribution to CMIP6: investigation of sea-level and ocean climate change in response to CO<sub>2</sub> forcing

“…Its global mean of 0.07 W m −2 is much smaller than the global mean F of 1.86 W m −2 (shown for individual models in Table 2). Thus it is apparently less important globally in our experiments than in the experiment of Garuba and Klinger (2016), who used an ocean-only model (rather than an AOGCM) with restoring boundary conditions. Both the magnitude and the time profile of the AMOC weakening in faf-heat are model-dependent (Fig.…”

“…2) are 0.57 W m −2 and 0.49 W m −2 (model mean Q, shown for each model in Table 2), so on average the feedback nearly doubles the heat input to this region. Garuba and Klinger (2016) call this effect the "redistribution feedback", and find it is about 70 % of the size of the added heat in the Atlantic. The imposed F and the feedback Q have remarkably similar distributions (Fig.…”

“…Most AOGCMs used for multidecadal simulations do not resolve ocean eddies at high latitudes, so their results will depend on their parametrisations of eddy advection on isoneutral surfaces (e.g. Gent and McWilliams, 1990;Griffies, 1998).…”

On the Relative Roles of the Atmosphere and Ocean in the Atlantic Multidecadal Variability

“…In this study we explicitly isolate the atmosphere‐ and ocean‐forced components of , in order to quantify their relative roles and to validate the mathematical formula derived from the conceptual model by Zhang (). First, we decompose ocean temperature variability into parts forced by the anomalous surface heat fluxes and ocean circulation using the passive tracer decomposition approach described in Banks and Gregory (), Xie and Vallis (), Bouttes et al (), Marshall et al (), Garuba and Klinger (), and Gregory et al (), except here we decompose ocean temperature anomalies due to internal variability rather than those due to CO 2 forcing as in these earlier studies. Further using the partial coupling approach introduced in Garuba et al (), we isolate the atmosphere‐forced component of the surface heat fluxes by preventing the ocean‐forced SST component from interacting with the atmosphere.…”