The impact of global warming on the tropical Pacific Ocean and El Niño

Collins, Matthew; An, Soon Il; Cai, Wenju; Ganachaud, Alexandre; Guilyardi, Éric; Jin, Fei; Jochum, Markus; Lengaigne, Matthieu; Power, Scott B.; Timmermann, Axel; Vecchi, Gabriel A.; Wittenberg, Andrew T.

doi:10.1038/ngeo868

Cited by 1,081 publications

(867 citation statements)

References 68 publications

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“…Such changes alter synoptic weather and the wind forcing of the ocean by the atmosphere, introducing another way for winds to generate multi-decadal changes in sea-ice. Therefore, in addition to the ways in which the occurrence and strength of SAM 37 , ENSO 38 and ice-sheet melt 39 may change, one must also consider how changes in the synoptic weather patterns may alter the future nature of winter sea-ice in the Southern Hemisphere.…”

Section: Discussionmentioning

confidence: 99%

Sources of heterogeneous variability and trends in Antarctic sea-ice

et al. 2015

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While the Northern Hemisphere sea-ice has uniformly declined over the past several decades, the observed sea-ice in the Southern Hemisphere has exhibited regions of increase and decrease. Here we use a comprehensive set of ocean-sea-ice simulations (1990)(1991)(1992)(1993)(1994)(1995)(1996)(1997)(1998)(1999)(2000)(2001)(2002)(2003)(2004)(2005)(2006)(2007) to elucidate the drivers of the observed heterogeneous sea-ice trends. We show wind variability is an important determinant of the heterogeneous pattern of the variability and trends in Southern Hemisphere sea-ice. Only in the West Pacific region does Southern Annular Mode wind forcing contribute significantly to the trend in sea-ice duration. El Niño Southern Oscillation wind forcing contribution to the sea-ice duration trend is confined to the Atlantic and Pacific. In the Indian Ocean, weather is a significant driver of the sea-ice duration trend. Only in the East Pacific region is wind forcing alone insufficient to give rise to the observed sea-ice decline and must be augmented by warming to reproduce the observations.

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Section: Discussionmentioning

confidence: 99%

Sources of heterogeneous variability and trends in Antarctic sea-ice

et al. 2015

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“…Understanding the local warming patterns is important, as they have consequences for changes in ocean circulation and regional climate (e.g., Vecchi and Soden 2007;Xie et al 2010;Collins et al 2010;Dai 2011).…”

Section: Introductionmentioning

confidence: 99%

Contribution of Increased Agulhas Leakage to Tropical Atlantic Warming

2015

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The upper tropical Atlantic Ocean has markedly warmed since the 1960s. It has been shown that this warming was not due to local heat fluxes and that the trade winds that drive the coastal and equatorial upwelling have intensified rather than weakened. Remote forcing might thus have played an important role. Here, model experiments are used to investigate the contribution from an increased inflow of warm Indian Ocean water through Agulhas leakage. A high-resolution hindcast experiment with interannually varying forcing for the time period 1948-2007, in which Agulhas leakage increases by about 45% from the 1960s to the early 2000s, reproduces the observed warming trend. To tease out the role of Agulhas leakage, a sensitivity experiment designed to only increase Agulhas leakage is used. Compared to a control simulation, it shows a pronounced warming in the upper tropical Atlantic Ocean. A Lagrangian trajectory analysis confirms that a significant portion of Agulhas leakage water reaches the upper 300 m of the tropical Atlantic Ocean within two decades and that the tropical Atlantic warming in the sensitivity experiment is mainly due to water of Agulhas origin. Therefore, it is suggested that the increased trade winds since the 1960s favor upwelling of warmer subsurface waters, which in part originate from the Agulhas, leading to higher SSTs in the tropics.

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“…AchutaRao and Sperber 2006; Guilyardi et al 2009a), which contributes to large uncertainties in our ability to anticipate and explain potential changes in El Niño characteristics. In fact, differences between coupled models are usually larger than the changes projected by each model under global warming conditions (van Oldenborgh et al 2005;Guilyardi 2006Guilyardi , 2009aCollins et al 2010). The reasons for these differences are related to two main factors-our incomplete understanding of ENSO dynamics, and a large number of different tuning parameters and parameterizations in the models that can lead to different physics of simulated El Niño.…”

Section: Introductionmentioning

confidence: 99%

How well do coupled models replicate ocean energetics relevant to ENSO?

2010

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Accurate replication of the processes associated with the energetics of the tropical ocean is necessary if coupled GCMs are to simulate the physics of ENSO correctly, including the transfer of energy from the winds to the ocean thermocline and energy dissipation during the ENSO cycle. Here, we analyze ocean energetics in coupled GCMs in terms of two integral parameters describing net energy loss in the system using the approach recently proposed by Brown and Fedorov (J Clim 23:1563-1580, 2010a and Fedorov (J Clim 20:1108(J Clim 20: -1117(J Clim 20: , 2007. These parameters are (1) the efficiency c of the conversion of wind power into the buoyancy power that controls the rate of change of the available potential energy (APE) in the ocean and (2) the e-folding rate a that characterizes the damping of APE by turbulent diffusion and other processes. Estimating these two parameters for coupled models reveals potential deficiencies (and large differences) in how state-of-the-art coupled GCMs reproduce the ocean energetics as compared to ocean-only models and data assimilating models. The majority of the coupled models we analyzed show a lower efficiency (values of c in the range of 10-50% versus 50-60% for ocean-only simulations or reanalysis) and a relatively strong energy damping (values of a -1 in the range 0.4-1 years versus 0.9-1.2 years). These differences in the model energetics appear to reflect differences in the simulated thermal structure of the tropical ocean, the structure of ocean equatorial currents, and deficiencies in the way coupled models simulate ENSO.

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The impact of global warming on the tropical Pacific Ocean and El Niño

Cited by 1,081 publications

References 68 publications

Sources of heterogeneous variability and trends in Antarctic sea-ice

Sources of heterogeneous variability and trends in Antarctic sea-ice

Contribution of Increased Agulhas Leakage to Tropical Atlantic Warming

How well do coupled models replicate ocean energetics relevant to ENSO?

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