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The ocean is a magnificent reservoir of kinetic energy possessed by currents at diverse spatio-temporal scales. These currents transport heat and material, regulating the regional and global climate. It is generally thought that large-scale ocean circulations should become more energetic under global warming, especially in the ocean’s upper layer. However, using high-resolution global climate simulations, here we demonstrate that the total ocean kinetic energy is projected to be significantly reduced in a warming climate, despite overall acceleration of large-scale ocean circulations in the upper layer. This reduction is primarily attributed to weakened ocean mesoscale eddies in the deep ocean. Enhanced vertical stratification under global warming reduces the available potential energy stored in large-scale ocean circulations, diminishing its conversion into eddy kinetic energy. Our findings reveal a more quiescent deep ocean under global warming and suggest a crucial role of mesoscale eddies in determining the anthropogenic change of total ocean kinetic energy.

Based on 22 of the climate models from phase 3 of the Coupled Model Intercomparison Project, we investigate the ability of the models to reproduce the spatiotemporal features of the wintertime North Pacific Oscillation (NPO), which is the second most important factor determining the wintertime sea level pressure field in simulations of the pre-industrial control climate, and evaluate the NPO response to the future most reasonable global warming scenario (the A1B scenario). We reveal that while most models simulate the geographic distribution and amplitude of the NPO pattern satisfactorily, only 13 models capture both features well. However, the temporal variability of the simulated NPO could not be significantly correlated with the observations. Further analysis indicates the weakened NPO intensity for a scenario of strong global warming is attributable to the reduced lower-tropospheric baroclinicity at mid-latitudes, which is anticipated to disrupt large-scale and low-frequency atmospheric variability, resulting in the diminished transfer of energy to the NPO, together with its northward shift.

Most El Niño events occur sporadically and peak in a single winter1–3, whereas La Niña tends to develop after an El Niño and last for two years or longer4–7. Relative to single-year La Niña, consecutive La Niña features meridionally broader easterly winds and hence a slower heat recharge of the equatorial Pacific6,7, enabling the cold anomalies to persist, exerting prolonged impacts on global climate, ecosystems and agriculture8–13. Future changes to multi-year-long La Niña events remain unknown. Here, using climate models under future greenhouse-gas forcings14, we find an increased frequency of consecutive La Niña ranging from 19 ± 11% in a low-emission scenario to 33 ± 13% in a high-emission scenario, supported by an inter-model consensus stronger in higher-emission scenarios. Under greenhouse warming, a mean-state warming maximum in the subtropical northeastern Pacific enhances the regional thermodynamic response to perturbations, generating anomalous easterlies that are further northward than in the twentieth century in response to El Niño warm anomalies. The sensitivity of the northward-broadened anomaly pattern is further increased by a warming maximum in the equatorial eastern Pacific. The slower heat recharge associated with the northward-broadened easterly anomalies facilitates the cold anomalies of the first-year La Niña to persist into a second-year La Niña. Thus, climate extremes as seen during historical consecutive La Niña episodes probably occur more frequently in the twenty-first century.

Antarctic shelf ocean warming affects melt of ice shelf/sheets and sea ice but projected changes vary vastly across climate models. A projected increase in El Niño variability has been found to slow future mid-latitude Southern Ocean warming but how this impacts the Antarctic shelf ocean is unknown. Here we show that a projected increase in El Niño variability accelerates Antarctic shelf ocean warming, hastening ice shelf/sheet melt but slowing sea ice reduction.

Equatorward alongshore winds over major eastern boundary upwelling systems (EBUSs) drive intense upwelling via Ekman dynamics, surfacing nutrient-rich deep waters and promoting marine primary production and fisheries. It is generally thought, dating back to Bakun’s hypothesis, that greenhouse warming should enhance upwelling in EBUSs by intensifying upwelling-favourable winds; yet this has not been tested. Here, using an ensemble of high-resolution climate simulations with improved EBUS representation, we show that long-term upwelling changes in EBUSs differ substantially, under a high-emission scenario, from those inferred by the wind-based upwelling index. Specifically, weakened or unchanged upwelling can coincide with intensified upwelling-favourable winds. These differences are linked to long-term changes of geostrophic flows that dominate upwelling changes in the Canary and Benguela currents and strongly offset wind-driven changes in the California and Humboldt currents. Our results highlight the controlling role of geostrophic flows in upwelling trends in EBUSs under greenhouse warming, which Bakun’s hypothesis overlooked.

The East China Sea Kuroshio (ECS‐Kuroshio) and the Ryukyu Current are the major poleward heat carriers in the North Pacific. Anomalous changes of ECS‐Kuroshio and Ryukyu Current could exert substantial influence on the climate in mid‐latitude regions. However, owing to limited observations and coarse resolution of climate models, how they might change under anthropogenic warming remains unknown. Here, we find an accelerating ECS‐Kuroshio (1.5 Sv) and a decelerating (−2.2 Sv) Ryukyu Current using in‐situ observation during 1958–2022, equivalent to 7% strengthening and 20% weakening in the 65 years. The trend is also simulated by four high‐resolution climate models, with multi‐model ensemble‐mean acceleration (deceleration) of the ECS‐Kuroshio (Ryukyu Current) of 1.2 ± 0.6 Sv (−6.2 ± 2.5 Sv) over 1950–2050. The weakening subtropical wind field reduces their summed transport o. Enhanced stratification, which induces uplift of current system and weaker topography‐flow interaction, leads to the intensifying ECS‐Kuroshio and disappearing Ryukyu Current. The East China Sea Kuroshio (ECS‐Kuroshio) and the Ryukyu Current are the major components of western boundary current (WBC) system in the North Pacific. They transport large amount of heat poleward, maintaining the mid‐latitude region warm and habitable. In this study, we find that in both observation and high‐resolution numerical models, the ECS‐Kuroshio is intensifying and the Ryukyu Current is rapidly declining. Particularly, in climate models, the Ryukyu Current is predicted to experience a 45% weakening during 1950–2050. Weakening wind field in the North Pacific tends to reduce the total transport of WBC system. The rapid weakening of the Ryukyu Current is credit to the enhanced stratification under global warming, which induces uplift of the Kuroshio east of Taiwan. Hence, less water will be blocked by bottom topography (Ilan Ridge) and bifurcates into the Ryukyu Current. Our finding highlights the needs for comprehensive studies on the local and climate effects of the evolution of the WBC system in the North Pacific. The East China Sea Kuroshio is intensifying while the Ryukyu Current is rapidly declining in a warming climateThe change is mainly caused by enhanced stratification which induces uplift of current system and weaker topography‐flow interaction The East China Sea Kuroshio is intensifying while the Ryukyu Current is rapidly declining in a warming climate The change is mainly caused by enhanced stratification which induces uplift of current system and weaker topography‐flow interaction

The El Niño/Southern Oscillation is characterized by irregular warm (El Niño) and cold (La Niña) events in the tropical Pacific Ocean, which have substantial global environmental and socioeconomic impacts. These events are generally attributed to the instability of basin-scale air–sea interactions in the equatorial Pacific. However, the role of sub-basin-scale processes in the El Niño/Southern Oscillation life cycle remains unknown due to the scarcity of observations and coarse resolution of climate models. Here, using a long-term high-resolution global climate simulation, we find that equatorial ocean eddies with horizontal wavelengths less than several hundred kilometres substantially inhibit the growth of La Niña and El Niño events. These submesoscale eddies are regulated by the intensity of Pacific cold-tongue temperature fronts. The eddies generate an anomalous surface cooling tendency during El Niño by inducing a reduced upward heat flux from the subsurface to the surface in the central-eastern equatorial Pacific; the opposite occurs during La Niña. This dampening effect is missing in the majority of state-of-the-art climate models. Our findings identify a pathway to resolve the long-standing overestimation of El Niño and La Niña amplitudes in climate simulations.

A majority of El Niño/Southern Oscillation (ENSO) events are preceded by the North Pacific Meridional Mode (NPMM), a dominant coupled ocean–atmospheric mode of variability. How the precursory NPMM forcing on ENSO responds to greenhouse warming remains unknown. Here, using climate model ensembles under high-emissions warming scenarios, we find an enhanced future impact on ENSO by the NPMM. This is manifested by increased sensitivity of boreal-winter equatorial Pacific winds and sea surface temperature (SST) anomalies to the NPMM three seasons before. The enhanced NPMM impact translates into an increased frequency of NPMM that leads to an extreme El Niño or La Niña. Under greenhouse warming, higher background SSTs cause a nonlinear evaporation–SST relationship to more effectively induce surface wind anomalies in the equatorial western Pacific, conducive to ENSO development. Thus, NPMM contributes to an increased frequency of future extreme ENSO events and becomes a more influential precursor for their predictability.

Global surface temperature short‐term trends fluctuate between cooling and fast‐warming under the combined action of external forcing and internal variability, significantly influencing the detectability of near‐term climate change. A key driver of these variations is anthropogenic aerosols (AAs), which have undergone a non‐monotonic evolution with rapid reduction in recent decades. However, their reduction is projected to decelerate under a high carbon emission scenario, yet the impact on surface temperature trends remains unknown. Here, using initial‐perturbation large ensembles, we find that future slowdown in AA reduction over Europe and North America expedites the subpolar North Atlantic surface warming by intensifying the Atlantic meridional overturning circulation. Further, it accelerates the South Indian Ocean and Southern Ocean surface warming through positive low‐cloud feedback and oceanic dynamical adjustment, triggered by the poleward migration of westerlies under interhemispheric energy constraint. These AA‐driven warmings exacerbate greenhouse warming, significantly enhancing the detectability of local decadal warming trends. Global surface temperature rises non‐monotonically, exhibiting phases of accelerated warming, warming slowdown, and transitions between warming and cooling. Anthropogenic aerosols (AAs) are a key driver of historical trend variations, making human‐induced trends more detectable. However, AAs follow a nonlinear trajectory with a rapid decline over Europe and North America in recent decades, and such reduction is projected to slow down in the future. The saturation of AA reduction signifies a diminishing proportion of anthropogenic forcings, which were previously considered unrelated to future global warming. Nevertheless, based on large ensembles of climate change simulations, we reveal that this projected slowdown in AA reduction could significantly accelerate surface warming in the subpolar North Atlantic, South Indian and Southern Oceans. This is achieved by the strengthening of Atlantic meridional overturning circulation and the coupled oceanic‐atmospheric adjustments triggered by the southward shift of southern westerlies. Those AA‐driven ocean surface warmings exacerbate greenhouse warming, significantly enhancing the predominance of external signals over strong internal noise and thus the detectability of regional human‐induced decadal warming trends. It suggests that upholding stringent AA mitigation policies is imperative for effectively mitigating the risk of severe ocean warming. Recent rapid reduction of anthropogenic aerosols (AA) over the northern extratropics would slow down under a high carbon emission scenarioSlower AA reduction accelerates subpolar North Atlantic surface warming by intensifying Atlantic meridional overturning circulationSlower AA reduction accelerates South Indian and Southern Ocean warming via positive low‐cloud feedback and oceanic dynamical adjustment Recent rapid reduction of anthropogenic aerosols (AA) over the northern extratropics would slow down under a high carbon emission scenario Slower AA reduction accelerates subpolar North Atlantic surface warming by intensifying Atlantic meridional overturning circulation Slower AA reduction accelerates South Indian and Southern Ocean warming via positive low‐cloud feedback and oceanic dynamical adjustment

Nowadays, lithium-sulfur batteries have attracted numerous attention due to their high specific capacity, high energy density, low cost and environmental benignancy. However, there are some critical challenges to be overcome such as low electronic conductivity and capacity fading caused by shuttle effect. Many attempts have been conducted to improve the electrochemical performance by designing effective sulfur hosts. In this paper, we synthesize a concrete-like sulfur/carbon cathode with high sulfur content (84%) by using 3D macroporous hosts with high pore volume. Sophisticated strategies of using polarized carbon framework and polymer coating are applied to synergistically control the dissolution of polysulfides so that the capacity retention and high rate performance can be remarkably enhanced. As a result, the composite exhibits a specific discharge capacity of 820 mAh g−1at a discharge current of 800 mA g−1(approximate to 0.5 C) after 100 cycles, calculated on the integrated mass of composite, which is superior to most report results.

The Pacific Decadal Oscillation (PDO) is the most prominent form of decadal variability over the North Pacific, characterized by its horseshoe-shaped sea surface temperature anomaly pattern1,2. The PDO exerts a substantial influence on marine ecosystems, fisheries and agriculture1–3. Through modulating global mean temperature, the phase shift of the PDO at the end of the twentieth century is suggested to be an influential factor in the recent surface warming hiatus4,5. Determining the predictability of the PDO in a warming climate is therefore of great importance6. By analysing future climate under different emission scenarios simulated by the Coupled Model Intercomparison Project phase 5 (ref. 7), we show that the prediction lead time and the associated amplitude of the PDO decrease sharply under greenhouse warming conditions. This decrease is largely attributable to a warming-induced intensification of oceanic stratification, which accelerates the propagation of Rossby waves, shortening the PDO lifespan and suppressing its amplitude by limiting its growth time. Our results suggest that greenhouse warming will make prediction of the PDO more challenging, with far-reaching ramifications.

Air‐sea exchanges across oceanic fronts are critical in powering cloud formation, precipitation, and atmospheric storms. Oceanic submesoscale fronts of scales 1–10 km are characterized by strong sea surface temperature (SST) gradients. However, it remains elusive how submesoscale fronts affect the overlying atmosphere due to a lack of high‐resolution observations or models. Based on rare high‐resolution in situ observations in the Kuroshio Extension region, we quantify the air‐sea exchanges across an oceanic submesoscale front. The cross‐front SST and turbulent heat flux gradients reaches 2.4°C/km and 47 W/m2/km, respectively, far stronger than that typically found in mesoscale‐resolving products. The stronger SST gradient drives substantially stronger air‐sea fluxes and vertical mixing than mesoscale fronts, enhancing cloud formations. The intense air‐sea exchanges across submesoscale fronts are confirmed in idealized model simulations, but not resolved in mesoscale‐resolving climate models. Our finding provides essential knowledge for improving simulations of cloud formation, precipitation, and storms in climate models. Oceanic fronts, characterized by large sea surface temperature (SST) gradients, are ubiquitous in the global ocean. Through intense heat and moisture release, these oceanic fronts induce large horizontal gradient of sea level pressure or increasing vertical mixing intensity in the lower atmosphere, are critical in powering cloud formation, precipitation, and atmospheric storms, but are sensitive to SST gradients. Oceanic submesoscale fronts of spatial scales 1–10 km are characterized by strong SST gradients. However, our knowledge of how the submesoscale fronts affect the overlying atmosphere is by and large void, due to a lack of high‐resolution observations or models. Here, based on high‐resolution in situ observations and model simulations, we show that submesoscale fronts drive much stronger air‐sea exchanges and vertical mixing as compared to mesoscale fronts, with significant implications for marine atmosphere boundary layer changes and cloud formations. Limited by the coarse resolution, the intense air‐sea exchanges across submesoscale fronts are not resolved in mesoscale‐resolving climate models. These results highlight the importance of submesoscale air‐sea interactions and call for a proper representation of submesoscale air‐sea exchanges in the next generation of climate models. Observations show strong gradient in sea surface temperature and turbulent heat flux across a submesoscale oceanic frontSubmesoscale fronts drive substantially stronger air‐sea fluxes and vertical mixing than mesoscale frontsThe intense air‐sea exchanges across submesoscale fronts are not resolved in mesoscale‐resolving climate models Observations show strong gradient in sea surface temperature and turbulent heat flux across a submesoscale oceanic front Submesoscale fronts drive substantially stronger air‐sea fluxes and vertical mixing than mesoscale fronts The intense air‐sea exchanges across submesoscale fronts are not resolved in mesoscale‐resolving climate models

The Sargasso Sea, accommodating marine species and mode water, is highly productive relative to other oligotrophic subtropical regions with intense air‐sea carbon and heat exchanges. Turbulent diapycnal mixing regulates these processes and is generally thought to be weakened in a more stratified ocean under anthropogenic forcing. However, by applying a finescale parameterization to long‐term hydrographic profiles collected during the Bermuda Atlantic Time‐Series Study (BATS), we show that its intensity has become stronger from 1994 to 2019 in the permanent thermocline. The enhanced turbulent diapycnal mixing is mainly attributed to the increase of wind power on internal waves along the Gulf Stream extension. Numerical simulations suggest that stronger internal waves excited along the Gulf Stream extension radiate downward and equatorward, causing enhanced turbulent diapycnal mixing in the northern Sargasso Sea including the BATS station. The findings have important implications for understanding responses of mode water and ecosystem in the Sargasso Sea to anthropogenic forcing. Turbulent mixing contributes to the vertical transport of heat, carbon and nutrients in the ocean, exerting significant effects on the ocean circulations and climate. It is thus important to know how turbulent mixing in the ocean will change under anthropogenic forcing. There is a prevailing thought that turbulent mixing should be weakened under anthropogenic forcing, as the enhanced stratification due to the faster warming in the upper than deeper ocean would hinder the processes generating turbulence. Here, using observation data sampled during the Bermuda Atlantic Time‐Series Study (BATS), we find that the turbulent mixing in the permanent thermocline there has increased by 42% over the past three decades. This positive trend is due to stronger wind energy input on internal waves that are gravity waves propagating within the ocean interior rather than on its surface. As these waves radiate downward and equatorward, they transfer their energy into smaller‐scale internal waves and eventually break, leading to enhanced turbulent mixing in the northern Sargasso Sea. Thermocline diapycnal mixing inferred from a finescale parameterization in the northern Sargasso Sea is enhanced from 1994 to 2019Enhanced thermocline diapycnal mixing in the northern Sargasso Sea is due to stronger internal waves excited by intensified winds Thermocline diapycnal mixing inferred from a finescale parameterization in the northern Sargasso Sea is enhanced from 1994 to 2019 Enhanced thermocline diapycnal mixing in the northern Sargasso Sea is due to stronger internal waves excited by intensified winds

The North Atlantic Ocean hosts the largest volume of global subtropical mode waters (STMWs) in the world, which serve as heat, carbon and oxygen silos in the ocean interior. STMWs are formed in the Gulf Stream region where thermal fronts are pervasive and result in feedback with the atmosphere. However, their roles in STMW formation have been overlooked. Using eddy-resolving global climate simulations, we find that suppressing local frontal-scale ocean-to-atmosphere (FOA) feedback leads to STMW formation being reduced almost by half. This is because FOA feedback enlarges STMW outcropping, attributable to the mixed layer deepening associated with cumulative excessive latent heat loss due to higher wind speeds and greater air-sea humidity contrast driven by the Gulf Stream fronts. Such enhanced heat loss overshadows the stronger restratification induced by vertical eddies and turbulent heat transport, making STMW colder and heavier. With more realistic representation of FOA feedback, the eddy-present/rich coupled global climate models reproduce the observed STMWs much better than the eddy-free ones. Such improvement in STMW production cannot be achieved, even with the oceanic resolution solely refined but without coupling to the overlying atmosphere in oceanic general circulation models. Our findings highlight the need to resolve FOA feedback to ameliorate the common severe underestimation of STMW and associated heat and carbon uptakes in earth system models.Frontal-scale ocean-to-atmosphere feedback determines the formation of subtropical mode water in the North Atlantic.

The Paris Agreement aims to constrain global mean temperature (GMT) increases to 2 °C above pre-industrial levels, with an aspirational target of 1.5 °C. However, the pathway to these targets and the impacts of a 1.5 °C and 2 °C warming on extreme El Niño and La Niña events—which severely influence weather patterns, agriculture, ecosystems, public health and economies—is little known. Here, by analysing climate models participating in the Climate Model Intercomparison Project’s Phase 5 (CMIP5; ref. ) under a most likely emission scenario, we demonstrate that extreme El Niño frequency increases linearly with the GMT towards a doubling at 1.5 °C warming. This increasing frequency of extreme El Niño events continues for up to a century after GMT has stabilized, underpinned by an oceanic thermocline deepening that sustains faster warming in the eastern equatorial Pacific than the off-equatorial region. Ultimately, this implies a higher risk of extreme El Niño to future generations after GMT rise has halted. On the other hand, whereas previous research suggests extreme La Niña events may double in frequency under the 4.5 °C warming scenario, the results presented here indicate little to no change under 1.5 °C or 2 °C warming.

Submesoscale eddies in the equatorial Pacific induce a pronounced upward heat flux from the subsurface to the surface ocean. Yet their response to greenhouse warming and feedback on the mean‐state change remain unknown. Using a long‐term high‐resolution climate simulation under a high carbon emission scenario, we show that submesoscale eddies in the central and eastern equatorial Pacific weaken, leading to an ∼50% reduction in their upward heat flux at the end of the 21st century, compared to its mid‐20th century level. This reduction is caused by an intensified stratification and a weakened cold tongue thermal front associated with a projected El Niño‐like warming pattern. The reduced vertical submesoscale eddy heat flux plays an important role in the anomalous heat budget of the surface layer over the central and eastern equatorial Pacific under greenhouse warming, acting as negative feedback on the El Niño‐like warming pattern. The central and eastern equatorial Pacific Ocean is abundant in submesoscale eddies, that is, filaments, fronts, and coherent vortices that have a horizontal scale ranging from several tens to hundreds of kilometers. These eddies transport heat from the subsurface to the surface ocean, providing an important heat source for the surface layer. So far, it remains unclear how the submesoscale eddies and their associated vertical heat flux will change under greenhouse warming. Using a long‐term high‐resolution climate simulation, we show that submesoscale eddies in the central and eastern equatorial Pacific will become weaker under a high carbon emission scenario. Their induced vertical heat flux will reduce by 50% at the end of the 21st century compared to its mid‐20th century level. The reduced vertical submesoscale eddy heat flux will retard the sea surface temperature increase in the central and eastern equatorial Pacific under greenhouse warming. Submesoscale eddies in the equatorial Pacific and their associated vertical heat flux are weakened under greenhouse warmingThe weakened vertical submesoscale eddy heat flux under greenhouse warming acts as negative feedback on the El Niño‐like warming pattern Submesoscale eddies in the equatorial Pacific and their associated vertical heat flux are weakened under greenhouse warming The weakened vertical submesoscale eddy heat flux under greenhouse warming acts as negative feedback on the El Niño‐like warming pattern

Increasing climate model resolution offers multifaceted benefits, such as improving modeled tropical cyclones. However, the extent to which it benefits El Niño‐Southern Oscillation (ENSO) simulation remains unknown. Here, comprehensive information on the sensitivity of ENSO performance to various resolutions is provided, based on a multi‐model and multi‐resolution ensemble of global coupled models. Overall, the reduced model biases of the equatorial sea surface temperature (SST) and precipitation mean state in higher‐resolution models may be attributed to increased oceanic resolution, and thus, better resolved eddy‐driven heat transport. ENSO spatial patterns were reproduced clearer in the eddy‐present models, likely due to the improved mean state and associated surface thermodynamic feedback. However, increasing atmospheric resolution alone deteriorates ENSO asymmetry, which may be due to the degradation of nonlinear atmospheric feedback. It remains challenging to alleviate the SST−shortwave‐flux feedback bias, which is a major source of too‐weak net heat flux feedback, irrespective of model resolution. The impact of model resolution on simulated weather and climate phenomena has received much attention in recent studies. In this study, we used seven global coupled models, at horizontal grid spacings ranging from 250 to 10 km, to assess El Niño‐Southern Oscillation (ENSO) performance in historical simulations from 1950 to 2014. Several metrics regarding the tropical Pacific mean states, ENSO characteristics, feedback processes, and teleconnections were evaluated. We found that in higher resolution models, the model biases of sea surface temperature and precipitation climatology in the equatorial Pacific had reduced, which may be because of the increased resolution of oceanic components. Such improvements would appear to be beneficial for a better representation of the ENSO spatial structure. However, solely refining the atmospheric resolution of climate models substantially degrades the reproduction of ENSO asymmetry and could conflict with the improvements made by the high‐resolution oceanic component. A comprehensive assessment of impacts from various resolutions offers a useful perspective for future model development. Higher oceanic resolution improves eddy‐induced heat transport, equatorial Pacific sea surface temperature (SST) and precipitation mean stateEddy‐present models improve El Niño‐Southern Oscillation (ENSO) patterns because of the realistic mean state and associated SST‐net heat flux feedbackSolely increasing the atmospheric resolution of coupled models exacerbates the bias of a too‐low ENSO asymmetry Higher oceanic resolution improves eddy‐induced heat transport, equatorial Pacific sea surface temperature (SST) and precipitation mean state Eddy‐present models improve El Niño‐Southern Oscillation (ENSO) patterns because of the realistic mean state and associated SST‐net heat flux feedback Solely increasing the atmospheric resolution of coupled models exacerbates the bias of a too‐low ENSO asymmetry

Relationship between Antarctic sea ice and the Southern Annular Mode and tropical climate variability has been widely studied. Focusing on the midlatitude oceanic frontal zones, this study identifies a fingerprint of South Atlantic (SA) variability in the Antarctic summer sea ice. The interaction between spring SA sea surface temperature (SST) and summer storm‐track activity modulates the hemispheric atmospheric circulation, which in turn alters Antarctic summer sea ice concentration (SIC) through thermal and wind‐driven forcing. Specifically, warm SST anomalies in the western SA frontal zone, corresponding to the strengthened SST front, cause the increased SIC in the eastern Ross Sea via anomalous cold air advection and offshore drift of sea ice. The opposite effect (i.e., warm air advection and onshore ice drift) results in the decreased SIC in the northwestern Weddell Sea. The findings also imply a potential impact of the midlatitude SA variability to the South Pole air temperature variability. Sea ice plays an important role in the global climate. In the context of global warming, small temperature changes can be amplified in polar regions by the positive feedback of sea ice. Many studies have revealed the relationship between Antarctic sea ice and major modes of climate variability, such as the Southern Annular Mode and El Niño/Southern Oscillation. A recent study found that warming reaching the South Pole is attributed by the tropical Pacific Ocean variability. However, little attention has been paid to the influence of midlatitude oceanic frontal zones. Here, we show that the interaction between the South Atlantic (SA) sea surface temperature (SST) in spring and storm‐track activity in summer induces anomalous hemispheric‐scale atmospheric circulation, which further modulates the summertime sea ice concentration (SIC) via both thermal and mechanical processes. Particularly, warm SST anomalies in the western SA frontal zone drive the anomalous high and low sea level pressure (SLP) over the Weddell and Ross Seas, resulting in the decreased and increased local SIC, respectively. Such anomalous high SLP over the Weddell Sea also induces anomalous warm air advection penetrating toward the South Pole. This reveals a potential connection between the midlatitude SA SST front and the South Pole air temperature. South Atlantic thermal front variations in spring modulate extratropical storm tracks and atmospheric circulation in summerThe planetary‐scale atmospheric response alters Antarctic summer sea ice concentration through thermal advection and wind‐driven driftRemarkable changes of sea ice concentration occur in the Weddell and Ross Seas South Atlantic thermal front variations in spring modulate extratropical storm tracks and atmospheric circulation in summer The planetary‐scale atmospheric response alters Antarctic summer sea ice concentration through thermal advection and wind‐driven drift Remarkable changes of sea ice concentration occur in the Weddell and Ross Seas

Storm tracks are a pivotal component in extratropical weather and climate. The sea surface temperature (SST) front in the midlatitude South Indian Ocean has been found to anchor the climatological core of the Southern Hemisphere (SH) storm tracks. However, on interannual‐to‐decadal timescales, observational and modeling evidence is presented here that the strengthened SST front in the midlatitude western South Atlantic (SA) can intensify the SH summer storm tracks by supplying more baroclinic energy, which overwhelms contributions from other oceanic frontal zones. Idealized experiments suggest that such a predominant impact on synoptic storms lies in the strengthened SA SST front acting in concert with the favorable thermal background produced in the presence of the Andes (i.e., enhancements of downstream low‐level temperature gradients and synoptic temperature variability). Our findings imply that oceanic variability in the western SA frontal zone could be a remote regulator of the SH extratropical summer climate variability. Storm tracks are identified as regions where synoptic storms are most prevalent in midlatitudes. They produce local weather extremes and maintain extratropical habitable climate by transporting heat, moisture, and momentum poleward and involve in climate variability via interacting with the low‐frequency flows. Regarding the long‐term mean state of the Southern Hemisphere (SH) storm tracks, the strongest sea surface temperature (SST) front in the midlatitude South Indian Ocean has been suggested to be crucial for maintaining the low‐level baroclinicity and thereby anchoring the storm‐track activity core. Regarding the interannual‐to‐decadal variability, however, we find that the strengthening of SST front in the midlatitude western South Atlantic (SA) is able to substantially intensify the whole SH storm‐track activity by fueling storm genesis, which overwhelms contributions made by the comparably strengthened SST fronts in the midlatitude South Indian Ocean and South Pacific. Such predominance lies in the strengthened SA SST front close to the downstream side of the Andes cooperating with the favorable low‐level thermal background produced in the presence of the Andes. Our findings imply that oceanic variability in the western SA frontal zone could remotely modulate the SH extratropical summer climate variability via altering storm tracks. Southern Hemisphere midlatitude oceanic variability strongly affects summer storm‐track activityThermal front change in the western South Atlantic rather than South Indian and South Pacific Oceans is the main driverThe presence of the Andes facilitates the predominant influence of the South Atlantic frontal variability on synoptic storms

Sea surface temperature (SST) is a key player in the air‐sea interaction, influencing storm tracks, atmospheric circulation, and climate modes. Although prevailing theories attribute variations of large‐scale SST to atmosphere forcing and ocean internal dynamics, we find that sea surface heat flux anomalies induced by mesoscale eddies exert significant influences on the upper‐ocean heat budget in the Kuroshio‐Oyashio extension region. Despite making nearly no contribution to the net heat exchange at the air‐sea interface, the eddy‐induced heat flux anomalies weaken the thermal stratification in the upper ocean and result in pronounced sea surface cooling. The underlying dynamics is the efficient dissipation of eddy potential energy by eddy‐induced heat flux anomalies. This makes the conversion of eddy potential energy to eddy kinetic energy significantly reduced, corresponding to a weaker eddy‐induced restratification flux. The finding complements the existing theories on large‐scale SST dynamics and has important implications for understanding extratropical climate variability. Sea surface temperature (SST) plays a fundamental role in the air‐sea interactions. At large scales (~1,000 km), it is traditionally thought that the atmospheric forcing drives the midlatitude SST variability. At mesoscales (~100 km), it is an ocean‐driven scenario where pronounced SST anomalies carried by ocean eddies exert an imprint on the atmospheric boundary layer. In this study, we find that such ocean mesoscale‐atmosphere (OME‐A) interactions have a significant influence on the large‐scale SST in the Kuroshio‐Oyashio extension region, complementing the existing views on the large‐scale SST dynamics. This is because the eddy‐induced heat flux anomalies damp the SST anomalies and thus available potential energy of eddies. Correspondingly, the conversion of eddy available potential energy to kinetic energy is significantly reduced in presence of OME‐A interactions, resulting in less heat transported from the subsurface to the surface region. Eddy‐induced surface heat flux anomalies act to dissipate the eddy potential energyEnhanced dissipation of eddy potential energy reduces its conversion to eddy kinetic energy, weakening the eddy restratification fluxThe reduced eddy restratification flux weakens the thermal stratification in the upper ocean and results in sea surface cooling