El Nino-Southern Oscillation Climate Research Articles

Changes in biogenic volatile organic compound emissions in response to the El Niño–Southern Oscillation

Abstract. Emissions of biogenic volatile organic compounds (BVOCs) from the terrestrial biosphere play a significant role in major atmospheric processes. BVOCs are highly reactive compounds that influence the atmosphere's oxidation capacity and also serve as precursors for the formation of aerosols that influence global radiation budgets. Emissions depend on the response of vegetation to atmospheric conditions (primarily temperature and light), as well as other stresses, e.g. from droughts and herbivory. The El Niño–Southern Oscillation (ENSO) is a naturally occurring cycle arising from anomalies in the sea surface temperature (SST) in the tropical Pacific. ENSO perturbs the natural seasonality of weather systems on both global and regional scales and is considered the most significant driver of climate variability. Several studies have evaluated the sensitivity of BVOC fluxes during ENSO events using historical transient simulations. While this approach employs realistic scenarios, it is difficult to assess the impact of ENSO alone given the multiple types of climate forcing, e.g. from anthropogenic emissions of CO2 and aerosol. In this study, a global atmospheric chemistry–climate model with enabled interactive vegetation was used to conduct two sets of simulations: (1) isolated ENSO event simulations, in which a single ENSO event is used to perturb otherwise baseline conditions, and (2) sustained ENSO simulations, in which the same ENSO conditions are reproduced for an extended period of time. From the isolated ENSO events, we present global and regional BVOC emission changes resulting from the immediate response of vegetation to atmospheric states. More focus is given to the sustained ENSO simulations, which have the benefit of reducing the internal variability for more robust statistics when linking atmospheric and vegetation variables with BVOC flux anomalies. Additionally, these simulations explore long-term changes in the biosphere with potential shifts in vegetation in this possible climate mode, accounting for the prospect of increased intensity and frequency of ENSO with climate change. Our results show that strong El Niño events increase global isoprene emission fluxes by 2.9 % and that one single ENSO event perturbs the Earth system so markedly that BVOC emission fluxes do not return to baseline emissions within several years after the event. We show that persistent ENSO conditions shift the vegetation to a new quasi-equilibrium state, leading to an amplification of BVOC emission changes with up to a 19 % increase in isoprene fluxes over the Amazon. We provide evidence that BVOC-induced changes in plant phenology, such as the leaf area index (LAI), have a significant influence on BVOC emissions in the sustained ENSO climate mode.

On the Impact of ENSO Cycles and Climate Change on Telescope Sites in Northern Chile

The Atacama desert stands as the most arid, non-polar, region on Earth and has accommodated a considerable portion of the world’s ground-based astronomical observatories for an extended period. The comprehension of factors important for observational conditions in this region, and the potential alterations induced by the escalating impact of climate change, are, therefore, of the utmost significance. In this study, we conduct an analysis of the surface-level air temperature, water vapour density, and astronomical seeing at the European Southern Observatory (commonly known by its acronym, ESO) telescope sites in northern Chile. Our findings reveal a discernible rise in temperature across all sites during the last decade. Moreover, we establish a correlation between the air temperature and water vapour density with the El Niño Southern Oscillation (ENSO) phases, wherein, the warm anomaly known as El Niño (EN) corresponds to drier observing conditions, coupled with higher maximum daily temperatures favouring more challenging near-infrared observations. The outcomes of this investigation have potential implications for the enhancement of the long-term scheduling of observations at telescope sites in northern Chile, thereby aiding in better planning and allocation of resources for the astronomy community.

Midwinter breakdown of ENSO climate impacts in East Asia

The El Niño-Southern Oscillation (ENSO) influence on the East Asian winter monsoon (EAWM) exhibits remarkable non-stationarity on subseasonal timescales, severely limiting climate predictability. Here, based on observational and reanalysis datasets, we identify a robust subseasonal variability in the EAWM response to ENSO, with a notable synchronous break in mid-January lasting about 10 days. We suggest that this breakdown is largely caused by interference from the abrupt phase reversal of the ENSO-driven North Atlantic Oscillation (NAO), which occurs about a week earlier in early January. During El Niño years, the NAO phase transition from positive to negative triggers a rapid change in the mid-latitude atmospheric circulation via the quasi-stationary Rossby wave adjustment. This results in the strengthening of the Siberian high, which produces strong northerly wind anomalies over East Asia, while the anomalous western North Pacific anticyclone weakens and shrinks to the south, eventually leading to the collapse of the teleconnection.

El Niño and other climatic drivers of epidemic malaria in Ethiopia: new tools for national health adaptation plans

BackgroundEthiopia has a history of climate related malaria epidemics. An improved understanding of malaria–climate interactions is needed to inform malaria control and national adaptation plans.MethodsMalaria–climate associations in Ethiopia were assessed using (a) monthly climate data (1981–2016) from the Ethiopian National Meteorological Agency (NMA), (b) sea surface temperatures (SSTs) from the eastern Pacific, Indian Ocean and Tropical Atlantic and (c) historical malaria epidemic information obtained from the literature. Data analysed spanned 1950–2016. Individual analyses were undertaken over relevant time periods. The impact of the El Niño Southern Oscillation (ENSO) on seasonal and spatial patterns of rainfall and minimum temperature (Tmin) and maximum temperature (Tmax) was explored using NMA online Maprooms. The relationship of historic malaria epidemics (local or widespread) and concurrent ENSO phases (El Niño, Neutral, La Niña) and climate conditions (including drought) was explored in various ways. The relationships between SSTs (ENSO, Indian Ocean Dipole and Tropical Atlantic), rainfall, Tmin, Tmax and malaria epidemics in Amhara region were also explored.ResultsEl Niño events are strongly related to higher Tmax across the country, drought in north-west Ethiopia during the July–August–September (JAS) rainy season and unusually heavy rain in the semi-arid south-east during the October–November–December (OND) season. La Niña conditions approximate the reverse. At the national level malaria epidemics mostly occur following the JAS rainy season and widespread epidemics are commonly associated with El Niño events when Tmax is high, and drought is common. In the Amhara region, malaria epidemics were not associated with ENSO, but with warm Tropical Atlantic SSTs and higher rainfall.ConclusionMalaria–climate relationships in Ethiopia are complex, unravelling them requires good climate and malaria data (as well as data on potential confounders) and an understanding of the regional and local climate system. The development of climate informed early warning systems must, therefore, target a specific region and season when predictability is high and where the climate drivers of malaria are sufficiently well understood. An El Niño event is likely in the coming years. Warming temperatures, political instability in some regions, and declining investments from international donors, implies an increasing risk of climate-related malaria epidemics.

Parasite communities of the golden snapper Lutjanus inermis (Perciformes: Lutjanidae): inter-annual variations during strange climatic events.

Strange oceanographic events such as El Niño and La Niña may have indirect effects on the local transmission processes of intestinal parasites due to the reduction or increase in populations of potential intermediate or definitive hosts. A total of 713 individuals of Lutjanus inermis (Peters) were collected over an 8-year period (October 2015 to July 2022) from Acapulco Bay, Mexico. Parasite communities in L. inermis were quantified and analysed to determine if they experienced interannual variations in species composition and structure as a result of local biotic and abiotic factors influenced by oceanographic events, such as El Niño-Southern Oscillation (ENSO), or La Niña, the cool phase of the ENSO climate pattern. Twenty-six taxa of metazoan parasites were recovered and identified: two Monogenea, eight Digenea, two Acanthocephala, four Nematoda, one Cestoda, seven Copepoda, and two Isopoda. Species richness at the component community level (8 to 17 species) was similar to reported richness in other species of Lutjanus Bloch. Parasite communities of L. inermis exhibited high inter-annual variation in the abundance of component species of parasite. However, the species richness and diversity were fairly stable over time. Climatic episodes of El Niño and La Niña probably generated notable changes in the structure of local food webs, thus indirectly influencing the transmission rates of intestinal parasite species. Changes in species composition and community structure of parasites possibly were due to variations in feeding behaviour during the events and differences in the host body size.

Marine shellfish exploitation as a means of reducing vulnerability to resource uncertainty in southern coastal Peru (200 BCE–150 CE)

The effects of El Niño Southern Oscillation (ENSO) are notoriously hazardous for human populations of the hyperarid Peruvian coast. Yet, ENSO climate fluctuations are fundamental to the ecology of desert plant and animal resources that have been incorporated into human subsistence economies for millennia. We examine marine shellfish exploitation among early complex societies in southern coastal Peru at the end of the first millenium BCE to better understand the subsistence vulnerability of communities in arid environments with variable resource availability and productivity. We analyze new shellfish data from Jahuay, a shoreline fishing settlement in the Topará Quebrada occupied amidst new regional social hierarchies and intensifying inner-valley agriculture. We compare mollusk taxonomic diversity and taxa rank order with published assemblages from four near-contemporaneous sites to assess local and regional trends in resource exploitation. At Jahuay, a unique focus on foraging plentiful Donax obesulus clams resistant to ENSO effects may reflect a local buffering strategy to ensure a resource supply through interannual and decadal climate oscillations. Our comparative results suggest regional reliance on intertidal resource patches, especially rocky habitats, for consumable shellfish. The relative convenience of gathering sessile intertidal taxa that form dense settlements may partly explain their regional popularity. The potential to dry and exchange mollusk meat as a protein source likely enhanced diet diversification while supporting economic and social relationships between communities. Overall, our findings imply that mollusks and intertidal foraging landscapes were important within a broad-spectrum subsistence strategy suited to maintaining and coordinating food availability in a dynamic environment.

Expanded agroecological niches and redistributed risks in northern Peru’s Chicama Valley during late-Holocene ENSO climate changes

South American arid lands present unique constellations of climatic risk to their human inhabitants, due to volatile events that can create markedly different hydroclimate conditions over interannual–centennial scales. However, a main driver of such volatility – the El Niño/Southern Oscillation (ENSO) – occurs with semiregular periodicity. Paleoclimatic and archeological evidence indicate not only that the strength and periodicity of ENSO patterns have changed over the late-Holocene, but their impacts were likely recognized, adapted to, and perhaps capitalized upon by agriculturalists employing adaptive risk strategies. We examine relationships over the last 1.3 kyr between ENSO periodicity, ecological transitions, and archeological settlement in Peru’s Chicama Valley through a coupled paleohydroclimate and agroecology model. We reconstruct periods when ENSO-like conditions dominated past hydroclimates and present a quantitative, spatially-explicit analysis of ecological productivity during modern ENSO-positive hydroclimate conditions. We show that archeological settlement patterns are sensitive to these transformations and reflect efforts to capitalize on expanded agroecological niches. Such expanded niches potentially offset the adverse impacts and risks associated with abrupt ENSO climate events. These results suggest archeological communities were aware of ENSO risk and managed productive strategies accordingly, highlighting the importance of a risk calculus that considers the net ecological effects of climate events.

Spatio-temporal variability of mean wave energy flux in the Caribbean Sea

Mean wave energy flux (hereinafter WEF) is assessed in the Caribbean Sea from a 60-year (1958–2017) wave hindcast. We use a novel approach, based on neural networks, to identify coherent regions of WEF and their association with different climate patterns. This method allows for a better evaluation of the underlying dynamics behind seasonal and inter-annual WEF variability, including the effect induced by the latitudinal migration of the Intertropical Convergence Zone (ITCZ) and the influence of El Niño-Southern Oscillation (ENSO) events. Results show regional differences in WEF variability likely due to both intensification and migration of the ITCZ. WEF exhibits a strong semi-seasonal signal in areas of the continental shelf, with maxima reached in January and June, in agreement with the known sea surface temperature and sea-level pressure variability patterns. At larger scales, WEF shows a significant correlation with the Oceanic Niño Index (ONI, which is the primary index for tracking the ocean part of ENSO climate pattern), depicting positive values in the central and western sides of the basin and negative ones at the eastern side.

Exploring ENSO-Induced Anomalies over North America in Historical and Future Climate Simulations That Use HadGEM2-ESM Output to Drive WRF

Projected changes to the El Niño Southern Oscillation (ENSO) climate mode have been explored using global Earth system models (ESMs). Regional expressions of such changes have yet to be fully advanced and may require the use of regional downscaling. Here, we employ regional climate modeling (RCM) using the Weather Research and Forecasting (WRF) model at convection-permitting resolution and nested in output from the HadGEM2 ESM. We quantify ENSO teleconnections to temperature and precipitation anomalies in historical and future climate scenarios over eastern North America. Two paired simulations are run, a strong El Niño (positive ENSO phase) and a weak La Niña (negative ENSO phase), for the historical and future years. The HadGEM2 direct output and HadGEM2-WRF simulation output are compared to the anomalies derived from the NOAA ENSO Climate Normals dataset. The near-surface temperature and precipitation differences by ENSO phase, as represented by the HadGEM2-WRF historical simulations, show a poor degree of association with the NOAA ENSO Climate Normals, in part because of the large biases in the HadGEM2 model. Downscaling with the WRF model does improve the agreement with the observations, and large discrepancies remain. The model chain HadGEM2-WRF reverses the sign of the ENSO phase response over eastern North America under simulations of the future climate with high greenhouse gas forcing, but due to the poor agreement with the NOAA ENSO Climate Normals it is difficult to assign confidence to this prediction.

Climate Anomalies and Spillover of Bat-Borne Viral Diseases in the Asia-Pacific Region and the Arabian Peninsula.

Climate variability and anomalies are known drivers of the emergence and outbreaks of infectious diseases. In this study, we investigated the potential association between climate factors and anomalies, including El Niño Southern Oscillation (ENSO) and land surface temperature anomalies, as well as the emergence and spillover events of bat-borne viral diseases in humans and livestock in the Asia–Pacific region and the Arabian Peninsula. Our findings from time series analyses, logistic regression models, and structural equation modelling revealed that the spillover patterns of the Nipah virus in Bangladesh and the Hendra virus in Australia were differently impacted by climate variability and with different time lags. We also used event coincidence analysis to show that the emergence events of most bat-borne viral diseases in the Asia–Pacific region and the Arabian Peninsula were statistically associated with ENSO climate anomalies. Spillover patterns of the Nipah virus in Bangladesh and the Hendra virus in Australia were also significantly associated with these events, although the pattern and co-influence of other climate factors differed. Our results suggest that climate factors and anomalies may create opportunities for virus spillover from bats to livestock and humans. Ongoing climate change and the future intensification of El Niño events will therefore potentially increase the emergence and spillover of bat-borne viral diseases in the Asia–Pacific region and the Arabian Peninsula.

ENSO and PDO related interannual variability in the north and east‐central part of the Bolivian Altiplano in South America

AbstractPrevious studies in this region focused on interannual and interdecadal precipitation variability during Dec–Feb (summer), relating the El Niño (EN) phase to droughts. Many studies examine this variability over different parts of the Altiplano, and mountainous terrain is well‐known for producing complex climate signals as well as variability over relatively small regions. Studies that have examined climate variability over the Altiplano suggest that the El Nino Southern Oscillation (ENSO) influence is complex. The monthly precipitation, maximum and minimum temperature from 1979 to 2017 are used to examine how ENSO and PDO (Pacific decadal oscillation) influence climate conditions. Power spectra analysis determined the periodicities, and analysis of variance was applied to standardized anomalies of the three variables to evaluate PDO and ENSO as variance factors. Frequency distributions were calculated by PDO and ENSO phases, and the differences were tested using the Chi‐square test. Our results suggest a PDO and ENSO influence, displaying more dry anomalies during DJF for EN/PDO(+), in agreement with a northward position of the Bolivian high. More wet anomalies during SON (Sep–Oct–Nov) in Neutral (NEU)/PDO(+) due to an upper‐level weak westerly flow during PDO(+). For maximum temperature, a reduction in cold anomalies during EN/PDO(−) was observed along with greater warm anomalies in JJA (Jun–Jul–Aug), SON and MAM (Mar–Apr–May). Similar results were observed for NEU phase, due to a greater occurrence of high pressures centres over the region during the PDO(−). Minimum temperature results displayed more variation within stations and a less clear response to ENSO compared to PDO. The research found a clear influence of PDO in the regional climatology associated with the influence of the upper‐level jet stream using the NCEP‐NCAR composites. This provided a better understanding of these two phenomena, which would allow the production of seasonal forecasts based on ENSO and PDO using both surface and upper‐level information.

ENSO, sun and megadroughts in SW USA during the last 11,000 years

El Niño Southern Oscillation (ENSO) is one of the most important modes of variability in the climate system. However, ENSO instrumental records are too short to characterize its natural variability at long-term timescales. Paleoclimate records showing ENSO variability during the Holocene on centennial and millennial timescales are rare but critical for our understanding of long-term multidecadal- to millennial-scale variability. Here we used several climate sensitive piñon pine (Pinus edulis) pollen records from the Southern Rockies, USA, to produce a detailed continuous record of effective precipitation and ENSO-like variability for the last 11,000 yrs. La Niña conditions dominated the Early Holocene while El Niño conditions enhanced in an increasing trend over the last 6,000 yrs. This trend was modulated by millennial-scale and ENSO-like hydrological activity at prominent 900-1,000-yr cycles and the amplitude of these cycles increased until present. Enhanced La Niña and related multidecadal megadroughts occurred in the Southern Rockies centered at ca. 10, 8, 6.8, 5.8, 4.8, 4, 3, 2.2, 1 ka. Insolation and solar output changes are suggested here as the main triggers for ENSO climate and vegetation changes. Our analysis of recent strong La Niña events, representing modern climate analogs of past conditions, indicates anomalously dry conditions persisting annually, leading to prolonged drought that impact piñon pine growth. Following the thermostat hypothesis and the Sun-ENSO link, such dry conditions are expected to prevail in the future, which combined with increasing temperatures, will most likely generate megadroughts in the SW USA.

Spatiotemporal dynamics of dengue in Colombia in relation to the combined effects of local climate and ENSO

Dengue virus (DENV) is an endemic disease in the hot and humid low-lands of Colombia. We characterize the association of monthly series of dengue cases with indices of El Niño/Southern Oscillation (ENSO) at the tropical Pacific and local climatic variables in Colombia during the period 2007-2017 at different temporal and spatial scales. For estimation purposes, we use lagged cross-correlations (Pearson test), cross-wavelet analysis (wavelet cross spectrum, and wavelet coherence), as well as a novel nonlinear causality method, PCMCI, that allows identifying common causal drivers and links among high dimensional simultaneous and time-lagged variables. Our results evidence the strong association of DENV cases in Colombia with ENSO indices and with local temperature and rainfall. El Niño (La Niña) phenomenon is related to an increase (decrease) of dengue cases nationally and in most regions and departments, with maximum correlations occurring at shorter time lags in the Pacific and Andes regions, closer to the Pacific Ocean. This association is mainly explained by the ENSO-driven increase in temperature and decrease in rainfall, especially in the Andes and Pacific regions. The influence of ENSO is not stationary, given the reduction of DENV cases since 2005, and that local climate variables vary in space and time, which prevents to extrapolate results from one region to another. The association between DENV and ENSO varies at national and regional scales when data are disaggregated by seasons, being stronger in DJF and weaker in SON. Overall, the Pacific and Andes regions control the relationship between dengue dynamics and ENSO at national scale. Cross-wavelet analysis indicates that the ENSO-DENV relation in Colombia exhibits a strong coherence in the 12 to 16-months frequency band, which implies the frequency locking between the annual cycle and the interannual (ENSO) timescales. Results of nonlinear causality metrics reveal the complex concomitant effects of ENSO and local climate variables, while offering new insights to develop early warning systems for DENV in Colombia.

Influence of ENSO and tropical Atlantic climate variability on flood characteristics in the Amazon basin

Abstract. Flooding in the Amazon basin is frequently attributed to modes of large-scale climate variability, but little attention is paid to how these modes influence the timing and duration of floods despite their importance to early warning systems and the significant impacts that these flood characteristics can have on communities. In this study, river discharge data from the Global Flood Awareness System (GloFAS 2.1) and observed data at 58 gauging stations are used to examine whether positive or negative phases of several Pacific and Atlantic indices significantly alter the characteristics of river flows throughout the Amazon basin (1979–2015). Results show significant changes in both flood magnitude and duration, particularly in the north-eastern Amazon for negative El Niño–Southern Oscillation (ENSO) phases when the sea surface temperature (SST) anomaly is positioned in the central tropical Pacific. This response is not identified for the eastern Pacific index, highlighting how the response can differ between ENSO types. Although flood magnitude and duration were found to be highly correlated, the impacts of large-scale climate variability on these characteristics are non-linear; some increases in annual flood maxima coincide with decreases in flood duration. The impact of flood timing, however, does not follow any notable pattern for all indices analysed. Finally, observed and simulated changes are found to be much more highly correlated for negative ENSO phases compared to the positive phase, meaning that GloFAS struggles to accurately simulate the differences in flood characteristics between El Niño and neutral years. These results have important implications for both the social and physical sectors working towards the improvement of early warning action systems for floods.

Recent trends in the fire dynamics in Brazilian Legal Amazon: Interaction between the ENSO phenomenon, climate and land use

The Brazilian Legal Amazon is an extensive territory (5,088,668.25 km2) in which different factors (environmental and social) influence the fire dynamics of the region. This study aims to explain the seasonal patterns of meteorological variables, fire, land use, and carbon emissions and their inter-relationships, focusing on years of El Niño–Southern Oscillation (ENSO) occurrence. For this purpose, we used data from fire foci and burned area obtained by the Moderate Resolution Imaging Spectroradiometer sensor and meteorological variables from Reanalysis 2. The kernel density was applied to the fire foci, and Spearman correlation coefficient between the foci and the other variables (fire foci, burned area, carbon emissions, evapotranspiration, wind speed, relative air humidity, rainfall, soil moisture, maximum temperature, minimum temperature, and mean air temperature) and Mann Kendall test for soybean, corn and sugarcane crops were performed. The years considered as La Niña were those with the highest fire foci, burned area, and carbon emissions. Our results show that even in periods considered as low fire risk, forests may be vulnerable to fires due to interaction with other variables. Furthermore, we found a tendency to increase the area planted with soybean, maize, and sugarcane, which may lead to more deforested areas in the region if there is no support from public policies. The uncertainty of the Legal Amazon's behavior towards climate change, combined with possible setbacks in Brazilian environmental policy due to the current government, highlights the importance of studies that encompass several factors such as this one.

Climate anomaly and palm oil price volatility in Indonesia

ENSO (El Niño Southern Oscillation) climate anomaly has become more frequent and stronger because of global warming and climate change. ENSO arguably plays a critical role in tropical countries such as Indonesia, primarily due to its intrinsic linkage with agricultural production and prices. This study examines one such relationship between ENSO and the price volatility of Crude Palm Oil (CPO), one of the most produced and consumed vegetable oils in the world. By applying time-series data from 2006 to 2018 and Ocean Nino Index (ONI) which serves as a proxy for the ENSO variable, this research used Autoregressive Conditional Heteroscedasticity (ARCH) methods to find out the CPO price volatility and Vector Error Correction Model (VECM) to investigate the impact of ENSO on the CPO price volatility. The results showed that the price volatility of CPO in Indonesia is low and will be persistent in the long term. ENSO affects the volatility of CPO prices in the long run, but there is no effect in the short run. The result is important for the stakeholders and government in preventing the risk and uncertainty condition of CPO price fluctuation caused by the climate anomaly.

Riscos de geadas em cultivos de batata na região de Guarapuava-PR em diferentes fases do ENOS

A condução de cultivos em condições de baixa previsibilidade da variabilidade climática pode ser considerado como um elemento de redução expressiva dos resultados de produção. A batata é definida como uma cultura sensível ao frio intenso, e no Sul do Brasil o ciclo de cultivo pode ocorrer em período de risco de eventos de geada. O estudo objetivou avaliar os riscos de ocorrência de geadas de diferentes intensidades durante o ciclo de desenvolvimento da cultura da batata em Guarapuava-PR, em diferentes períodos de cultivo nas distintas fases do ENOS. Utilizou-se série histórica de dados climáticos de 43 anos, entre 1976 e 2018. As análises foram realizadas com estatística descritiva utilizando-se índices de porcentagem e normalização de conjunto de dados. Os dados foram agrupados em períodos decendiais para os meses de agosto a outubro e março a maio, em que existe frequência de geadas e possibilidade de lavouras de batata em desenvolvimento no campo. Dentre os principais resultados verificou-se que o período de plantio, com minimização dos riscos de ocorrência de geadas para a cultura na região de Guarapuava, é compreendido entre 21 de setembro e 31 de janeiro em ambas as fases do ENOS, El Niño e La Niña e neutralidade climática. De forma geral o cultivo de batata em anos de neutralidade está sujeito à maiores riscos de perdas por ocorrência de geadas quando comparados com o plantio em anos de fenômeno El Niño e La Niña.

The role of low‐level circulation on water vapour transport to central and northern South America: Insights from a 2D Lagrangian approach

AbstractThe potential role of low‐level circulation on the transport of atmospheric moisture towards Central America and northern South America is studied with the Dynamical Recycling Model (DRM) for the period 1981–2015. The net 2D field for advection of moisture in the DRM is estimated based on two different approaches: from the Vertically Integrated Moisture Flux (VIMF) and from a linear combination of low‐level winds (Ueff). The relative importance of low‐level wind structures is inferred from the comparison of both DRM approaches. The Ueff approach yields larger long‐term estimates of transport from the Pacific compared to the VIMF approach, largely associated with the effect of the low‐level circulation over the eastern Pacific, known as the Choco Jet (CJ). Large differences in the transport estimated by both approaches also appear to be associated with different phases of El Niño‐Southern Oscillation (ENSO), when differences in the low‐level circulation take place over the eastern Pacific and the tropical Atlantic. Similar differences are found for anomalous activity of the CJ and the Caribbean Low‐level Jet (CLLJ). The differences in the magnitude of long‐term estimates and anomalies from both 2D approaches show that details in vertical wind shear are important for the estimation of water vapour transport. However, the sign of the anomalies and correlation patterns under different circulation regimes were the same for both methods. Furthermore, with both approaches, it is found that variability in the low‐level circulation over the eastern Pacific and the tropical Atlantic is substantially related to changes in the vapour transport towards Central America and northern South America. In addition, the robustness of this signal suggests that a simple 2D tool like the DRM may be effectively used to study transport changes under different regimes, like different ENSO phases or climate change scenarios.

Contrasting dissolved organic carbon concentrations in the Bransfield Strait, Northern Antarctic Peninsula: insights into ENSO and SAM effects

The marine reservoir of dissolved organic carbon (DOC) is equivalent to the atmospheric carbon reservoir and represents the largest reduced carbon stock in the ocean. However, the role of DOC in the global carbon cycle is not fully understood. In this study, we analyzed the distribution of DOC in the water column of the Bransfield Strait, Northern Antarctic Peninsula. Data were collected during two summer cruises of the NAUTILUS project conducted by the Brazilian High Latitude Oceanography Group in February 2015 and 2016. We investigated the possible effects of the El Niño - Southern Oscillation (ENSO) and Southern Annular Mode (SAM) climate modes on DOC variability based on correlations between DOC and temperature, salinity, and dissolved oxygen. Concentrations of DOC ranged from 40.70 to 122.82 μmol kg−1 in 2015 and 33.12 to 112.20 μmol kg−1 in 2016. The analysis shows that the vertical distribution of DOC in the Bransfield Strait may be controlled by a combination of vertical stratification, vertical export of organic matter and biological activity in the upper mixed layer during summertime. The significant interannual differences observed between DOC concentration and most physicochemical parameters may be linked to ENSO and SAM climate modes. The highest DOC concentration was observed in February 2015, associated with a layer of warm surface water, due to the higher stratification of the water column. The ENSO and SAM climate modes were low and positive in that year, favoring intrusions of waters from the Antarctic Circumpolar Current. In contrast, February 2016 was characterized by record positive ENSO and SAM modes. The intensification of the Weddell Gyre induced the advection of cold, more oxygenated and recently formed shelf waters into the Bransfield Strait, which may have contributed to the lower DOC concentrations. This study contributes to a better understanding of the role of DOC in the global carbon cycle in a region of complex ocean circulation and mixing, and sensitive to global climate change.

Effect of ENSO and IOD on the Variability of Sea Surface Temperature (SST) in Java Sea

El-Niño Southern Oscillation (ENSO) and Indian Ocean Dipole (IOD) climate variability are global climate variability that can affect oceanographic conditions including SST (Sea Surface Temperature). Located between two oceans, the Indian and the Pacific, the variability of SST in Indonesia is influenced by ENSO and IOD. Previous studies have shown that the influence of ENSO in the Java Sea depends on the season, and while positive (negative) IOD decreases (increase) SST in Indonesian seas. This study aims to examine the effect of ENSO and IOD climate variability on the variability of SST in the Java Sea. SST data are obtained from NOAA Pathfinder and Aqua MODIS satellite image data, while wind data is obtained from ECMWF satellite imagery with long observed data for 36 years (1982-2017) using quantitative methods in spatial and temporal, we found that the influence of ENSO and IOD in Java Sea based on the intensity of the anomaly. The intensity of ENSO which is stronger can affect SST more than IOD.