Fast and Slow Responses to Global Warming: Sea Surface Temperature and Precipitation Patterns

Abstract

The time-dependent response of sea surface temperature (SST) to global warming and the associated atmospheric changes are investigated based on a 1% yr 21 CO 2 increase to the quadrupling experiment of the Geophysical Fluid Dynamics Laboratory Climate Model, version 2.1. The SST response consists of a fast component, for which the ocean mixed layer is in quasi equilibrium with the radiative forcing, and a slow component owing to the gradual warming of the deeper ocean in and beneath the thermocline. A diagnostic method is proposed to isolate spatial patterns of the fast and slow responses. The deep ocean warming retards the surface warming in the fast response but turns into a forcing for the slow response. As a result, the fast and slow responses are nearly opposite to each other in spatial pattern, especially over the subpolar North Atlantic/Southern Ocean regions of the deep-water/bottom-water formation, and in the interhemispheric SST gradient between the southern and northern subtropics. Wind-evaporation-SST feedback is an additional mechanism for the SST pattern formation in the tropics. Analyses of phase 5 of the Coupled Model Intercomparison Project (CMIP5) multimodel ensemble of global warming simulations confirm the validity of the diagnostic method that separates the fast and slow responses. Tropical annual rainfall change follows the SST warming pattern in both the fast and slow responses in CMIP5, increasing where the SST increase exceeds the tropical mean warming.

Distinctive Evolutions of Eurasian Warming and Extreme Events Before and After Global Warming Would Stabilize at 1.5 °C

“…As global warming reaches stabilization, SST keeps robust and persistent warming over the midlatitudes of both Northern and Southern Hemispheres (Figures d–f). These results are like the fast and slow SST responses investigated in Long et al (); both researches suggest prolonged warming in the western North Pacific. We have looked at the near‐global mean ocean temperature changes in the 1.5 °C, 1.5 °C OS, and 2 °C cases (figures not shown).…”

Dependence of global radiative feedbacks on evolving patterns of surface heat fluxes

“…Subtle changes in wind stress or ocean circulation might have a small direct influence in terms of net heat uptake but a large indirect impact on surface temperature, through modifying feedback magnitudes. How much of the disagreement among models in simulated feedback strengths is due to the difference among the models in ocean heat uptake patterns [Winton et al, 2010] or ocean heat-uptake-induced SST changes [Long et al, 2014]? What is the physical mechanism of ocean heat uptake and cloud response and how does it evolve in the coupled system [Rose and Rayborn, 2016;Trossman et al, 2016]?…”

“…What is the physical mechanism of ocean heat uptake and cloud response and how does it evolve in the coupled system [Rose and Rayborn, 2016;Trossman et al, 2016]? How much of the disagreement among models in simulated feedback strengths is due to the difference among the models in ocean heat uptake patterns [Winton et al, 2010] or ocean heat-uptake-induced SST changes [Long et al, 2014]? The use of a constant global feedback parameter in intermediate complexity models, prediction, and impact studies should be-depending on the purpose of use-carefully considered and may turn out to be problematic.…”

What would happen to Superstorm Sandy under the influence of a substantially warmer Atlantic Ocean?

“…The total area of the warm pool (SST > 29°C) in FSST is more than doubled compared to PSST. Additionally, the water along and off the Atlantic coast from Florida to New England and the northeast coast of Canada is also much warmer by 1–3° C. This pattern of SST warming has been attributed to enhanced heat content in the upper oceans in the tropics and an increase in ocean heat transport in the Gulf Stream under global warming [ Xie et al , ; Long et al , ].…”