ABSTRACT Interannual climate variability strongly influences renewable energy availability, making it a critical factor for achieving UN Sustainable Development Goals (SDGs). However, our knowledge about the potential solar and wind energy production in tropical South America and its relation to ocean‐atmospheric modes of variability is limited; modes such as El Niño/Southern Oscillation (ENSO), the Atlantic Meridional Mode (AMM), among others. Therefore, we investigate the influence of these modes on solar and wind energy. We apply partial correlations and composite analyses to reanalysis and satellite data to identify the processes connecting large‐scale ocean‐atmospheric variability to seasonal anomalies in renewable power generation. Our study identifies three energy hubs as regions with high climatological mean energy availability: The north Caribbean (NC), eastern Brazil (EB) and western Perú/Bolivia (WPB). ENSO influences the sea level pressure (SLP) gradients, generating wind anomalies that directly affect the wind capacity factor (CF). ENSO also affects the solar CF through reduced atmospheric moisture transport and convergence, which results in fewer clouds leading to higher‐than‐average surface radiation or by atmospheric subsidence. ENSO impacts the NC and EB hubs, with weaker effects in the WPB hub. The AMM is associated with cross‐equatorial wind anomalies that modulate wind CF, as well as moisture convergence and cloud cover, thereby influencing solar CF. Wind CF in the NC and EB hubs is inversely modulated by the AMM, weakening winds and reducing radiation over the NC and strengthening winds and increasing radiation on the EB. The Atlantic equatorial El Niño mode (Atl3) exerts minor effects, with anomalies confined to the equatorial Atlantic. Overall, we find limited complementarity between solar and wind energy at interannual time‐scale. Our results provide insights for forecasting energy production and managing energy storage for periods of low renewable energy availability.

Tropical South America's hydroclimate is influenced by ocean–atmospheric variability modes (drivers of climate variability). It is still not known which physical mechanisms teleconnect the Atlantic modes of variability with South America's soil moisture, net radiation, and terrestrial evaporation (evapotranspiration). Understanding these mechanisms is essential to predict the response of ecosystems. This study uses composites of reanalysis and satellite data to identify the processes linking land–surface anomalies and ocean–atmospheric modes. It estimates the control soil moisture and net radiation impose on evapotranspiration (categorised as water- or energy-limited regimes). It shows that these two local controllers of evapotranspiration are influenced by the position of the Intertropical Convergence Zone (ITCZ). However, the evapotranspiration anomalies are driven by the phase of each climate mode, which alter water and radiation availability. The Atlantic Meridional Mode (AMM) generates cross-equatorial wind anomalies that affect moisture convergence, which in turn modify the cloud cover, precipitation, soil moisture, radiation availability, and hence evapotranspiration. The anomalies have important geographical differences depending on the season analysed; they migrate from the east in austral autumn towards the central Amazon and western Orinoco in austral spring. The Atlantic Niño Equatorial mode (Atl3) affects evapotranspiration in the Guianas and eastern Orinoco by means of pressure and trade wind variability, which in turn affect local hydrometeorological conditions and evapotranspiration. Both Atlantic modes mainly impact regions different from those impacted by El Niño–Southern Oscillation (ENSO), although northeast Brazil and the Guianas might experience overlapping effects. Therefore, these ocean–atmospheric modes impact the water, energy, and carbon cycles; they might influence regional climate extremes (e.g. droughts and floods); and they are critical for achieving sustainable development goals (SDGs).

El Niño/Southern Oscillation (ENSO) strongly impacts the hydroclimate of tropical South America. However, other ocean-atmospheric oscillations in the Atlantic also have teleconnections over the continent with the most extensive tropical rainforest; these oscillations influence hydroclimate extremes (i.e. droughts and floods). Our research focuses on the physical mechanisms that link the Atlantic Sea Surface Temperature conditions with the hydrological anomalies, i.e. soil moisture, streamflow and evaporation. This research is grounded on the consistency of a multi-evidence approach between datasets. We use independent observations of land-surface and atmospheric variables whose robustness comes from gauges, physically consistent interpolations (i.e. reanalysis), simulations or satellite-based observations. The research focuses on the satellite era (1980-) to compare several datasets. Apart from the Amazon, other important basins such as the Orinoco, Magdalena and Tocantis have received little attention; hence, we also focused on them. The Atlantic Meridional Mode (AMM) consists of cross-equatorial Sea Level Pressure anomalies that deflect climatological winds northward or southward. Hence, the seesaw of wind anomalies produces anomalous atmospheric transport, convergence and precipitation. When dividing the analysis by independent seasons, the results show changing impacts over different subbasins of the Orinoco and Amazon. On the other hand, the Atlantic El Niño/La Niña (Atl3) weakens or strengthens the trade winds from June to August, producing moisture convergence or divergence over the Guianas and eastern Orinoco. The SST impact on evaporation is a complex consequence of the anomalous atmospheric circulation. The cascade of abnormal atmospheric circulation modifies not just the surface water but also the radiation availability, causing hydrological anomalies. The radiation anomalies combined with the soil moisture memory control the evaporation anomalies. This dynamic also depends on the season analysed.

The Modern Era Reanalysis (ModE-RA) is a global monthly paleo-reanalysis covering the period between 1421 and 2008. To reconstruct past climate fields an offline data assimilation approach is used, blending together information from an ensemble of transient atmospheric model simulations and observations. In the early period, ModE-RA utilizes natural proxies and documentary data, while from the 17th century onward instrumental measurements are also assimilated. The impact of each observation on the reconstruction is stored in the observation feedback archive, which provides additional information on the input data such as preprocessing steps and the regression-based forward models. The monthly resolved reconstructions include estimates of the most important climate fields. Furthermore, we provide a reconstruction, ModE-RAclim, which together with ModE-RA and the model simulations allows to disentangle the role of observations and model forcings. ModE-RA is best suited to study intra-annual to multi-decadal climate variability and to analyze the causes and mechanisms of past extreme climate events.

The ongoing discussion about the AMOC slowdown over the 21st century requires a detailed understanding of preindustrial AMOC variability. Here, we present a surface nudging technique to reconstruct the AMOC variability during the Little Ice Age from 1450–1780 CE. The AMOC reconstruction is based on a 10-member ensemble ocean model simulation nudged to proxy-reconstructed sea surface temperature. This approach validates and improves existing knowledge of the AMOC variability, showing that the AMOC slowdown under stable atmospheric CO2 conditions is mainly driven by a 4 to 7 year lagged effect of surface heat flux associated with the North Atlantic Oscillation.

The Amazon Basin, the largest watershed on Earth, experienced a significant increase in wet-season precipitation and high-season river discharge from the early 1990s to early 2010s. Some studies have linked the increased Amazon Basin hydrologic cycle to decadal trends of increased Pacific trade winds, eastern Pacific sea surface temperature (SST) cooling, and associated strengthening of the Pacific Walker circulation. However, it has been difficult to disentangle the role of Pacific decadal variability from the impacts of greenhouse gases and other external climate drivers over the same period. Here, we separate the contributions of external forcings from those of Pacific decadal variability by comparing two large ensembles of climate model experiments with identical radiative forcing agents but imposing different tropical Pacific wind stress. One ensemble constrains tropical Pacific wind stress to its long-term climatology, suppressing tropical Pacific decadal variability; the other ensemble imposes the observed tropical Pacific wind stress anomalies, simulating realistic tropical Pacific decadal variability. Comparing the Amazon Basin hydroclimate response in the two ensembles allows us to distinguish the contributions of external forcings common to both simulations from those related to Pacific trade wind variability. For the 1992–2012 trend, the experiments with observed tropical Pacific wind stress anomalies simulate strengthening of the Walker circulation between the Pacific and South America and sharpening of the Pacific–Atlantic interbasin SST contrast, driving increased Amazon Basin wet-season precipitation and high-season discharge. In contrast, these circulation and hydrologic intensification trends are absent in the simulations with climatological tropical Pacific wind stress. This work underscores the importance of Pacific decadal variability in driving hydrological cycle changes and modulating the hydroclimate impacts of global warming over the Amazon Basin.

Climate models predict a strengthening contrast between wet and dry regions in the tropics and subtropics (30°S-30°N), and data from the latest model intercomparison project (CMIP6) support this expectation. Rainfall in ascending regions increases, and in descending regions decreases in both climate model and reanalysis data. This strengthening contrast can be captured by tracking rainfall change each month in the wettest and driest third of the tropics and subtropics combined. Since wet and dry regions are selected individually for each model ensemble member, and the observations, and for each month, this analysis is largely unaffected by biases in location of precipitation features. Blended satellite and in situ data support the model-simulated tendency to sharpening contrasts between wet and dry regions, with rainfall in wet regions increasing substantially contrasted by a slight decrease in dry regions. These new datasets allow us to detect with more confidence the effect of external forcings on these changes, attribute them for the first time to the response to anthropogenic and natural forcings separately, and determine that the observed trends are statistically larger than the model responses. Our results show that the observed change is best explained by increasing greenhouse gases with natural forcing contributing some increase following the drop in wet region precipitation after Mount Pinatubo, while anthropogenic aerosol effects are expected to show a weak tropic-wide trend at the present time of flat global aerosol forcing. As expected from climate models, the observed signal strengthens further when focusing on the wet tail of spatial distributions in both models and data.

The sea surface temperature (SST) contrast between the Northern Hemisphere (NH) and Southern Hemisphere (SH) influences the location of the intertropical convergence zone (ITCZ) and the intensity of the monsoon systems. This study examines the contributions of external forcing and unforced internal variability to the interhemispheric SST contrast in HadSST3 and ERSSTv5 observations, and 10 models from phase 5 of the Coupled Model Intercomparison Project (CMIP5) from 1881 to 2012. Using multimodel mean fingerprints, a significant influence of anthropogenic, but not natural, forcing is detected in the interhemispheric SST contrast, with the observed response larger than that of the model mean in ERSSTv5. The forced response consists of asymmetric NH-SHSST cooling from the mid-twentieth century to around 1980, followed by opposite NH-SH SST warming. The remaining best-estimate residual or unforced component is marked by NH-SHSST maxima in the 1930s andmid-1960s, and a rapid NH-SHSST decrease around 1970. Examination of decadal shifts in the observed interhemispheric SST contrast highlights the shift around 1970 as the most prominent from 1881 to 2012. Both NH and SHSST variability contributed to the shift, which appears not to be attributable to external forcings. Most models examined fail to capture such large-magnitude shifts in their control simulations, although some models with high interhemispheric SST variability are able to produce them. Large-magnitude shifts produced by the control simulations feature disparate spatial SST patterns, some of which are consistent with changes typically associated with the Atlantic meridional overturning circulation (AMOC).

This review addresses the causes of observed climate variations across the industrial period, from 1750 to present. It focuses on long-term changes, both in response to external forcing and to climate variability in the ocean and atmosphere. A synthesis of results from attribution studies based on palaeoclimatic reconstructions covering the recent few centuries to the 20th century, and instrumental data shows how greenhouse gases began to cause warming since the beginning of industrialization, causing trends that are attributable to greenhouse gases by 1900 in proxy-based temperature reconstructions. Their influence increased over time, dominating recent trends. However, other forcings have caused substantial deviations from this emerging greenhouse warming trend: volcanic eruptions have caused strong cooling following a period of unusually heavy activity, such as in the early 19th century; or warming during periods of low activity, such as in the early-to-mid 20th century. Anthropogenic aerosol forcing most likely masked some global greenhouse warming over the 20th century, especially since the accelerated increase in sulphate aerosol emissions starting around 1950. Based on modelling and attribution studies, aerosol forcing has also influenced regional temperatures, caused long-term changes in monsoons and imprinted on Atlantic variability. Multi-decadal variations in atmospheric modes can also cause long-term climate variability, as apparent for the example of the North Atlantic Oscillation, and have influenced Atlantic ocean variability. Long-term precipitation changes are more difficult to attribute to external forcing due to spatial sparseness of data and noisiness of precipitation changes, but the observed pattern of precipitation response to warming from station data supports climate model simulated changes and with it, predictions. The long-term warming has also led to significant differences in daily variability as, for example, visible in long European station data. Extreme events over the historical record provide valuable samples of possible extreme events and their mechanisms.

We present a binned product of sea surface temperature, sea surface salinity, and sea surface density data in the North Atlantic subpolar gyre from 1993 to 2017 that resolves seasonal variability along specific ship routes (https://doi.org/10.6096/SSS-BIN-NASG). The characteristics of this product are described and validated through comparisons to other monthly products. Data presented in this work were collected in regions crossed by two predetermined ship transects, between Denmark and western Greenland (AX01) and between Iceland, Newfoundland, and the northeastern USA (AX02). The data were binned along a selected usable transect. The analysis and the strong correlation between successive seasons indicate that in large parts of the subpolar gyre, the binning approach is robust and resolves the seasonal timescales, in particular after 1997 and in regions away from the continental shelf. Prior to 2002, there was no winter sampling over the West Greenland Shelf. Variability in sea surface salinity increases towards Newfoundland south of 54 degrees N, as well as in the western Iceland Basin along 59 degrees N. Variability in sea surface temperature presents less spatial structure with an increase westward and towards Newfoundland. The contribution of temperature variability to density dominates in the eastern part of the gyre, whereas the contribution of salinity variability dominates in the southwestern part along AX02.

We present a binned annual product (BINS) of sea surface temperature (SST), sea surface salinity (SSS), and sea surface density (SSD) observations for 1896–2015 of the subpolar North Atlantic between 40° N and 70° N, mostly excluding the shelf areas. The product of bin averages over spatial scales on the order of 200 to 500 km, reproducing most of the interannual variability in different time series covering at least the last three decades or of the along-track ship monitoring. Comparisons with other SSS and SST gridded products available since 1950 suggest that BINS captures the large decadal to multidecadal variability. Comparison with the HadSST3 SST product since 1896 also indicates that the decadal and multidecadal variability is usually well-reproduced, with small differences in long-term trends or in areas with marginal data coverage in either of the two products. Outside of the Labrador Sea and Greenland margins, interannual variability is rather similar in different seasons. Variability at periods longer than 15 years is a large part of the total interannual variability, both for SST and SSS, except possibly in the south-western part of the domain. Variability in SST and SSS increases towards the west, with the contribution of salinity variability to density dominating that of temperature in the western Atlantic, except close to the Gulf Stream and North Atlantic Current in the southwest area. Weaker variability and larger relative temperature contributions to density changes are found in the eastern part of the gyre and south of Iceland.

In the original publication of the article Figs. 6 and 7 were published incorrectly. The correct figures are given below. The original article has been corrected.

Sea surface salinity (SSS) is a major ocean circulation component and indicator of the hydrological cycle. Here we investigate an unprecedented Atlantic SSS compilation from 1896 to 2013 and analyze the main modes of SSS decadal variability. Using principal component analysis, we find that the low‐latitude (tropical and subtropical) Atlantic and the subpolar Atlantic have distinct variability. Subpolar and low‐latitude SSS are negatively correlated, with subpolar anomalies leading low‐latitude anomalies by about a decade. Subpolar SSS varies in phase with the Atlantic Multidecadal Oscillation (AMO), whereas low‐latitude SSS varies in phase with the North Atlantic Oscillation (NAO). Additionally, northern tropical SSS is anticorrelated with Sahel rainfall, suggesting that SSS reflects the Intertropical Convergence Zone latitude. The 1896–2013 SSS trend shows amplification of the mean SSS field, with subpolar freshening and low‐latitude salinification. The AMO and NAO have little effect on the long‐term trend but contribute to the trend since 1970.