Trans-basin Atlantic-Pacific connections further weakened by common model Pacific mean SST biases

Abstract

A robust eastern Pacific surface temperature cooling trend was evident between ~1990–2013 that was considered as a pronounced contributor to the global surface warming slowdown. The majority of current climate models failed to reproduce this Pacific cooling trend, which is at least partly due to the underrepresentation of trans-basin teleconnections. Here, we investigate whether common Pacific mean sea surface temperature biases may further diminish the Atlantic-Pacific trans-basin induced Pacific cooling. Our results suggest that background Pacific SST biases act to weaken the trans-basin teleconnection by strengthening the Atlantic atmospheric stability and reducing Atlantic convection. These Pacific SST biases also act to substantially undermine the positive zonal wind-SST feedback. Furthermore, when combined, the Pacific and Atlantic SST biases led to Pacific cooling response that is almost non-existent (underestimated by 89%). Future efforts aim at reducing the model mean state biases may significantly help to improve the simulation skills of trans-basin teleconnections.

North Atlantic as a Trigger for Pacific‐Wide Decadal Climate Change

“…A recent study assessing 13 coupled model idealized AMV pacemaker simulations points out that the intermodel spread varies by a factor of 10 (Ruprich‐Robert et al., 2021), mostly stemming from model precipitation mean‐state biases‐induced moist static energy injected into the upper troposphere from the Atlantic surface. Earlier studies have also stressed that the Pacific‐wide decadal variability is underrepresented in coupled models because of the tropical Atlantic SST mean‐state biases (Kajtar et al., 2016; McGregor et al., 2018) or the tropical Pacific mean‐state biases (Li et al., 2020). These coupled model mean‐state errors limit our ability to better understand the decadal‐scale inter‐basin Atlantic‐Pacific interactions.…”

Changing El Niño–Southern Oscillation in a warming climate

“…For the projected long-term mean state changes, the competing processes between the atmospheric damping differential and the oceanic thermostat mechanism also operate, whereas multidecadal internal variability has a diminishing role. State-of-the-art climate models also underestimate inter-basin interactions 37,41,[94][95][96] , which might contribute to the long-term faster warming in the equatorial EP than would otherwise be the case 41 . Additional factors that influence future mean state changes include the impact of off-equatorial Pacific Ocean warming, ENSO rectification and cold tongue bias in climate models.…”

Uncertainty in El Niño-like warming and California precipitation changes linked by the Interdecadal Pacific Oscillation

“…Similar to CA winter precipitation, there is also substantial uncertainty in the El Niño- vs. La Niña-like (i.e., stronger SST warming in the tropical western Pacific relative to the eastern Pacific) warming pattern over the tropical Pacific under global warming 36 – 38 . In contrast with the controversial role of internal variability in the CA winter precipitation, the possible role of internal variability in the future El Niño-like warming pattern has yet to be brought to the fore, although there is an ongoing debate on the relative roles of model bias 38 , 39 vs. internal variability 40 – 42 in the La Niña-like warming pattern observed in the recent decades. With the convolved contributions of model uncertainty and internal variability to the large uncertainty in the El Niño-like warming and CA precipitation, CMIP simulations offer limited opportunities to isolate the roles of internal variability in their respective future changes and their relationships.…”