ENSO induces coherent climate anomalies over the Indo-western Pacific, but these anomalies outlast SST anomalies of the equatorial Pacific by a season, with major effects on the Asian summer monsoon. This review provides historical accounts of major milestones and synthesizes recent advances in the endeavor to understand summer variability over the Indo-Northwest Pacific region. Specifically, a large-scale anomalous anticyclone(AAC) is a recurrent pattern in post-El Ni ?no summers, spanning the tropical Northwest Pacific and North Indian oceans. Regarding the ocean memory that anchors the summer AAC, competing hypotheses emphasize either SST cooling in the easterly trade wind regime of the Northwest Pacific or SST warming in the westerly monsoon regime of the North Indian Ocean. Our synthesis reveals a coupled ocean–atmosphere mode that builds on both mechanisms in a two-stage evolution. In spring, when the northeast trades prevail, the AAC and Northwest Pacific cooling are coupled via wind–evaporation–SST feedback. The Northwest Pacific cooling persists to trigger a summer feedback that arises from the interaction of the AAC and North Indian Ocean warming, enabled by the westerly monsoon wind regime. This Indo-western Pacific ocean capacitor(IPOC) effect explains why El Ni ?no stages its last act over the monsoonal Indo-Northwest Pacific and casts the Indian Ocean warming and AAC in leading roles. The IPOC displays interdecadal modulations by the ENSO variance cycle, significantly correlated with ENSO at the turn of the 20 th century and after the 1970 s, but not in between. Outstanding issues, including future climate projections, are also discussed.
To meet the low warming targets proposed in the 2015 Paris Agreement,substantial reduction in carbon emissions is needed in the future.It is important to know how surface climates respond under low warming targets.The present study investigates the surface temperature changes under the low-forcing scenario of Representative Concentration Pathways(RCP2.6)and its updated version(Shared Socioeconomic Pathways,SSP1-2.6)by the Flexible Global Ocean-Atmosphere-Land System(FGOALS)models participating in phases 5 and 6 of the Coupled Model Intercomparison Project(CMIP5 and CMIP6,respectively).In both scenarios,radiative forcing(RF)first increases to a peak of 3 W m^−2 around 2045 and then decreases to 2.6 W m^−2 by 2100.Global mean surface air temperature rises in all FGOALS models when RF increases(RF increasing stage)and declines or holds nearly constant when RF decreases(RF decreasing stage).The surface temperature change is distinct in its sign and magnitude between the RF increasing and decreasing stages over the land,Arctic,North Atlantic subpolar region,and Southern Ocean.Besides,the regional surface temperature change pattern displays pronounced model-to-model spread during both the RF increasing and decreasing stages,mainly due to large intermodel differences in climatological surface temperature,ice-albedo feedback,natural variability,and Atlantic Meridional Overturning Circulation change.The pattern of tropical precipitation change is generally anchored by the spatial variations of relative surface temperature change(deviations from the tropical mean value)in the FGOALS models.Moreover,the projected changes in the updated FGOALS models are closer to the multi-model ensemble mean results than their predecessors,suggesting that there are noticeable improvements in the future projections of FGOALS models from CMIP5 to CMIP6.
With a scientific consensus reached regarding the anthropogenic effect on global mean temperature, developing reliable regional climate projections has emerged as a new challenge for climate science. A national project was launched in China in 2012 to study ocean's role in regional climate change. This paper starts with a review of recent advances in the study of regional climate re-sponse to global warming, followed by a description of the Chinese project including the rationale, objectives, and plan for field ob-servations. The 15 research articles that follow in the special issue are highlighted, representing some of the initial results from the project.
Climate models project a positive Indian Ocean Dipole(p IOD)–like SST response in the tropical Indian Ocean to global warming. By employing the Community Earth System Model and applying an overriding technique to its ocean component(version 2 of the Parallel Ocean Program), this study investigates the similarities and differences of the formation mechanisms for the changes in the tropical Indian Ocean during the p IOD versus global warming. Results show that their formation processes and related seasonality are quite similar; in particular, wind–thermocline–SST feedback is the leading mechanism in producing the anomalous cooling over the eastern tropics in both cases. Some differences are also found, including the fact that the cooling effect of the vertical advection over the eastern tropical Indian Ocean is dominated by the anomalous vertical velocity during the p IOD but by the anomalous upper-ocean stratification under global warming. These findings are further examined through an analysis of the mixed layer heat budget.
Mode water is a distinct water mass characterized by a near vertical homogeneous layer or low potential vorticity, and is considered essential for understanding ocean climate variability. Based on the output of GFDL CM3, this study investigates the response of eastern subtropical mode water(ESTMW) in the North Pacific to two different single forcings: greenhouse gases(GHGs) and aerosol. Under GHG forcing, ESTMW is produced on lighter isopycnal surfaces and is decreased in volume. Under aerosol forcing, in sharp contrast, it is produced on denser isopycnal surfaces and is increased in volume.The main reason for the opposite response is because surface ocean-to-atmosphere latent heat flux change over the ESTMW formation region shoals the mixed layer and thus weakens the lateral induction under GHG forcing, but deepens the mixed layer and thus strengthens the lateral induction under aerosol forcing. In addition, local wind changes are also favorable to the opposite response of ESTMW production to GHG versus aerosol.
