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A declining trend in Indian summer monsoon precipitation (ISMP) in the latter half of the 20th century is a scientifically challenging and societally relevant research issue. Heavy aerosol loading over India is one of the key factors in modulating the ISMP. Using the state-of-the-state-of-the-art chemistry-climate model, ECHAM6-HAMMOZ, the impacts of South Asian anthropogenic sulfate aerosols on the Indian summer monsoon precipitation were investigated against: (1) 2010 La Niña (excess monsoon), (2) 2015 El Niño (deficit monsoon) in comparison to (3) normal monsoon 2016. Sensitivity simulations were designed with 48% enhancement in South Asian SO 2 emissions based on a trend estimated from Ozone Monitoring Instrument (OMI) satellite observations during 2006–2017. The model simulations showed that sulfate aerosols reduce ISMP by 27.5%–43.3 %, while simulations without sulfate loading enhanced ISMP by 23% in 2010 La Niña and reduction by 35% in 2015 El Niño. This paper reports that sulfate aerosols loading over India reduce precipitation by aerosol-induced direct and indirect effects by inducing atmospheric cooling, weakening in the convection, and reduction in moisture transport to Indian landmass. This paper emphasizes the necessity of alternate use of energy to reduce sulfate aerosol emissions to solve water issues in South Asia. [Display omitted] • Sulfate emission reduces Indian summer monsoon precipitation through aerosol-radiation and aerosol-cloud interactions. • Over 27% of the summer monsoon rainfall deficit in a normal year are linked to Asian anthropogenic sulfate emissions. • Sulfate-induced rainfall reduction is the maximum for La Niña year. • SO 2 loading increases atmospheric stability and weakens moisture transport to India. [ABSTRACT FROM AUTHOR]

• First high-accuracy prediction of global SST at 0.25° spatial resolution and 2 time scales (daily and monthly) based on deep learning. • Fully consider the spatiotemporal correlations in historical time series by attention mechanism to improve prediction accuracy. • Superior to widely-adopted deep learning models (3D-CNN, ConvLSTM, and LSTM) and numerical model (HYCOM). • Applicable to climate change sensitive area. Sea Surface Temperature (SST) is an essential parameter of the ocean–atmosphere system, so accurately predicting the future SST is of great significance. To address the low prediction accuracy due to insufficient consideration of spatiotemporal correlations in existing machine learning models, this paper proposes an Effective Attention Model (EAM) to achieve daily global SST prediction (predicting the SST of the next 15 days using those of the past 15 days) and monthly global SST prediction (predicting the SST of the next 12 months using those of the past 12 months). The EAM adopts an attention mechanism to avoid information redundancy and improve prediction accuracy. This is the first work to realize high-accuracy global SST prediction with a high spatial resolution of 0.25° on two time scales (daily and monthly) based on deep learning. Experiments show that (1) the prediction results have a consistent global spatiotemporal distribution with the ground truth, with the Root Mean Squared Difference (RMSD) of daily prediction ranging from 0.212 to 0.932 ℃ and the RMSD of monthly prediction ranging from 0.666 to 0.782 ℃. The EAM is superior to the deep learning models (ConvLSTM, 3D-CNN, and LSTM) and the numerical model (HYCOM); (2) Besides global prediction, the EAM also achieves good performance in a climate change sensitive area (Niño 3.4 sea area), with the lowest RMSD of 0.231 ℃. This study may not only benefit the research on climate events (El Niño and La Niña) but also serve to predict other marine disasters (such as heat waves and storms). In the future, the proposed attention module can also be adapted to other prediction scenarios such as meteorology. [ABSTRACT FROM AUTHOR]

The Mindanao Dome (MD) upwelling system has important implications for the local and even the global air-sea interaction, but its changing process in hydroecological conditions and response mechanism influenced by ENSO cycle are still unclear. The evolution of MD upwelling process and the changes in hydro-climatic environments in MD region in three typical El Niño, La Niña, and normal years during ENSO event from 2010 to 2015 are analyzed. Results reveal that migration of surface water is the main factor controlling the changes in the intensity of the MD upwelling during this ENSO cycle but not the variations in wind stress curl. Massive westward accumulation (eastward movement) of surface warm water and strengthened (weakened) upwelling Rossby waves together induce the enhancement (weakness) of the MD upwelling during mature phase of 2015/2016 El Niño (2010/2011 La Niña) year. In addition, NECC and MD upwelling together control the biological activities in surface waters in MD region during this ENSO cycle. The meandering NECC and MD upwelling both strengthen (weaken) when 2015/2016 El Niño (2010/2011 La Niña) occur, which transport more (less) nutrients to surface sea from horizontal and vertical levels, respectively, leading to an increase (decrease) in surface Chl- a. Two synopsis mechanisms are proposed to illustrate the response mechanism of the MD upwelling evolution and eco-hydro-climatic variations in the MD region to 2015/2016 El Niño (2010/2011 La Niña) event, respectively. This paper highlights the prospect for the role played by ENSO cycle in local ecological effects and hydro-climatic evolution, which further has profound implications for understanding the influence of the global climate change on the ocean carbon cycle. • Surface water migration controlled the MD upwelling variation during ENSO cycle from 2010 to 2015. • Surface biological activity is controlled by NECC and MD upwelling during ENSO cycle. • Two conceptual maps of the oceanic process changes during El Niño and La Niña events are proposed. [ABSTRACT FROM AUTHOR]

The 4.2 ka event was a period of global drought and climate cooling linked to the widespread disruption of Neolithic culture. However, the detailed climatic changes during this period are not completely understood. In this paper, we report a high-resolution pollen record for the Dayanghu wetland in the Zhejiang region of southeastern China, which we use to infer mean annual precipitation (MAP) fluctuations during the period spanning 4600–4000 calendar years before present (cal. yr BP). There was a long-term trend of decreasing MAP during this interval, consistent with weakening of the East Asian Summer Monsoon since the mid-Holocene. This trend was punctuated by episodes of relatively high MAP at 4350–4320, ca. 4260, and 4220–4200 cal. yr BP, and extreme droughts at 4200 and 4150 cal. yr BP. We propose that solar activity promoted El Niño events and contributed to dramatic MAP fluctuations in the Dayanghu wetland. La Niña events and negative-phase intervals of the Pacific Decadal Oscillation may have been responsible for the extreme drought at 4200–4150 cal. yr BP. In summary, we propose a close relationship between MAP and solar forcing, with short-term enhanced solar activity increasing the intensity of the East Asian Summer Monsoon and contributing to increasing decadal variability in the inner tropical Pacific, which ultimately leads to increased precipitation variability in southeast China. The results improve our understanding of the detailed climatic features of the 4.2 ka event. • High-resolution pollen record for ca. 4.2 ka for the Zhejiang region, China. • Pollen-based mean annual precipitation was quantitatively reconstructed. • Long-term droughts tended to occur during 4600–4000 cal. yr BP. • La Niña-dominated ENSO contributed to a catastrophic drought at 4200–4150 cal. yr BP. [ABSTRACT FROM AUTHOR]

Australia has long been observed to experience the ENSO (El Niño Southern Oscillation) of periodic alternation of flooding and drought. Australia has experienced consecutive years of the La Niña cycle of heavy rain and flooding. At some stage, this will revert to one or more years of drought, often severe. In previous years of drought, consideration was given to alternative water supply, including recycled wastewater. This paper reflects on the case of the previous period of El Niño drought in South East Queensland (SEQ), aiming to contribute to drought mitigation planning through reviving consideration of recycled water. • In depth case study on Queensland response to drought conditions. • Includes analysis of attempts to introduce other water sources, particularly recycled water for potable and non potable uses. • Examines reasons for failure and non-acceptance and uses comparisons with successful schemes to suggest policy changes for a way forward. [ABSTRACT FROM AUTHOR]

Historically, La Niña events typically follow El Niño events, particularly in case of prolonged La Niña events that succeed strong El Niño events. However, the current triple-dip La Niña (CTD-La Niña) event during 2020–2023 occurred after a neutral event rather than a (strong) El Niño, which differs from the two historical triple-dip La Niña (HTD-La Niña; 1973–1976 and 1998–2001) events since 1950. Therefore, this paper aims to investigate the unique evolution and potential formation mechanisms of the CTD-La Niña event. Our results show that, in contrast to the HTD-La Niña, the CTD-La Niña event is not primarily influenced by tropical processes themselves. Instead, the consecutively in-phase (negative) North Pacific Meridional Mode and South Pacific Meridional Mode play a crucial role in initiating and sustaining the La Niña event of 2020–2023 through tropical-extratropical interactions. On one hand, their associated negative sea surface temperature (SST) anomalies extend toward the equatorial central Pacific each year from spring to summer, leading to negative SST and strengthening easterly surface wind anomalies in the equatorial Pacific. On the other hand, their related northeastern and southeastern wind stress can modify the wind stress curl over the equatorial Pacific, further intensifying the equatorward Ekman transport from the off-equator. These factors together provide favorable conditions for the re-occurrence of the La Niña event from 2020 to 2023. These findings may offer valuable insights into understanding the formation of long-lasting ENSO events. • The current triple-dip La Niña (CTD-La Niña) event during 2020–2023 occurred after a neutral event rather than an (strong) El Niño. • The consecutively in-phase (negative) NPMM and SPMM play a crucial role in initiating and sustaining the 2020–2023 La Niña event through tropical-extratropical interactions. • The NPMM made almost equally contributions in each consecutive year, whereas the SPMM started off relatively small in the first year and gradually strengthened thereafter to sustain the development of the CTD-La Niña event. [ABSTRACT FROM AUTHOR]

Abstract: The effects of El Nino and La Nina have been considered as the major variables in weather changes in the Middle East. This issue has been shown by regression indexes in a number of papers. The presented study has proven that the El Nino and La Nina should be added to the weather forecast variables because of their major effects. Weather forecasts could be influenced by some variables that have uncertainty, so the deterministic approaches may lead to incorrect predictions. The proposed algorithm can be used when some variables have uncertainty. In this study, a probabilistic approach has been chosen to show the effect of El Nino and La Nina on the monthly maximum temperature. Different ENSO Indices have been proposed for El Nino or La Nina occurrences but each of them has some deficiencies. In order to overcome the drawback of using one of the ENSO Indices, the fuzzy based analysis approach has been chosen in this paper. Data from Chabahar, one of the stations in the south of Iran, has been chosen for the algorithm to be applied on. MATLAB has been used to run the algorithm on the data. The results show that El Nino and La Nina lead to major effect on the amount of monthly maximum temperature in the south of Iran. [Copyright &y& Elsevier]

Rainfall erosivity (RE) is the ability of rainfall to cause soil or regolith erosion. Understanding the spatial distribution and temporal trends of RE is critical for assessing soil erosion risk and improving upon soil conservation planning. The aim of this paper is to study the temporal and spatial changes in RE in the Huaihe River Basin, China. This will be based on daily precipitation data from 67 meteorological stations in the Huaihe River Basin for the period 1971 to 2016. The assessment of the resulting RE values involved inverse distance-weighted (IDW) interpolation, Sen's slope estimation, and the Mann-Kendall nonparametric test. In addition, the possible influence of the El Niño – Southern Oscillation (ENSO) on RE in the Huaihe River Basin will be examined by the use of Cross Wavelet Transform (XWT) and Wavelet Coherence (WTC), where the relationship between RE and the multivariate ENSO index (MEI) are analyzed. The results showed that the spatial distribution of RE is characterized by it increasing from west to east and north to south. In most areas, the annual RE has increased slightly, while this upward trend in the southeastern part of the study area was more significant. The rainfall erosivity of rainstorms (RE-SM) in the Huaihe River Basin played a leading role in the annual RE, and 97% of the stations displayed the order of importance of the different categories of rainfall as rainfall erosivity of rainstorms (RE-SM) > rainfall erosivity of heavy rain (RE-HR) > rainfall erosivity of moderate rain (RE-MR). Over monthly time scales, the RE was the highest in July, while it was lowest in December, with the monthly differences being apparent. The RE in the Huaihe River Basin were relatively large during non-El Niño/La Niña periods and relatively small during El Niño/La Niña periods. Finally, correlations between RE and the MEI in various parts of the basin showed different characteristics over time and space, with both displaying similarities and differences. • Spatial–temporal variations in rainfall erosivity in the study area were quantified. • Rainfall erosivity of rainstorms (RE-SM) dominates in different categories of rainfall erosivity. • El Niño and La Niña events have different impacts on rainfall erosivity in the Huaihe River Basin. [ABSTRACT FROM AUTHOR]

Based on monthly rainfall station data from the National Climate Prediction Center of China Meteorological Administration, reanalysis monthly data from NCEP/NCAR including the monthly mean and long-term mean values for geopotential height, winds of multi-levels, NOAA(National Oceanic and Atmospheric Administration) monthly Sea Surface Temperature (ERSSTV5), the causes of anomalous excessive precipitation in 2021/2022 winter over South China (SC) are investigated by Liang-Kleeman information flow, composite and wave flux methods. The results show that the winter precipitation over SC in 2021/2022 DJF is far more than normal, and the associated circulation patterns are obviously different from those induced by traditional La Niña, especially in the Atlantic and East Asia areas south to Lake Baikal. In 2021/2022 DJF, the Tibet Plateau (TP) exists anomalous cyclone with strong ascending motion, which directly affects the circulation patterns in Eastern China and thus the precipitation in SC. It is a significant causal relationship for the earlier season velocity potential at 850 hPa (related to the anomalous SST) over the tropical Atlantic to later DJF anomalous vertical motions over TP. Especially when the anomalies in tropical Atlantic leads one month before, the relationship is closest. The anomalies of the tropical Atlantic can stimulate the Rossby wave train which propagates downstream, corresponding to the abnormal cyclonic circulation over TP. In the early autumn to winter of 2021/2022, the 850 hPa potential velocity anomalies in the tropical Atlantic were significant with positive phase. The Rossby wave train excited by the potential velocity anomalies and then propagated along the great circle path and global jet stream (GJT) over South Asia (SA), formed an anomalous cyclonic with ascending motion over TP and lead more precipitation over SC in winter of 2021/2022. Winter rainfall, usually accompanying with lower temperature, will bring severely bad influence on traffic, power supply, communication, agriculture and people's lives. The results of this paper can provide a reference for further understanding the causes and mechanism of DJF rainfall over SC. • The winter precipitation over SC in 2021/2022 DJF is extremely more than normal, and the associated circulation patterns are obviously different from those induced by La Niña, especially in the Atlantic and East Asia areas south to Lake Baikal. • Strong ascending motion over TP(Tibet Plateau) affects the circulation patterns directly in eastern China and lead to the excessive precipitation in SC during 2021/2022 DJF. • The anomalies over the tropical Atlantic can stimulate the Rossby wave train and propagate downstream, and the Rossby wave trains allow energy to propagate to TP area with wave flux convergent, contributing certainly to the anomaly cyclone circulation there. [ABSTRACT FROM AUTHOR]

The majority of present-day and future global warming is related to various positive feedbacks in the climate system that tend to amplify the initial radiative forcing from increasing greenhouse gases in the atmosphere. One essential positive feedback is the rise in upper tropospheric water vapor (UTWV) or the specific humidity (SH) that acts as an intense greenhouse gas trapping in additional heat released from the Earth's surface. In this paper we expand on previous studies showing that the interannual variability of UTWV in the tropical and extratropical climates is strongly linked with the El Nino-Southern Oscillation (ENSO). We have expanded on previous studies by looking at the response of the long-term UTWV concentrations to the ENSO over a 41-year period (1979–2019) using the ERA5 reanalysis data. For the first time we look at the physical mechanism for the El Nino and La Nina connections to UTWV that is shown to be related to changes in deep convection over the central and eastern Pacific Ocean. In agreement with previous studies, we find that El Nino years have positive anomalies in UTWV, while in La Nina years there are negative anomalies in UTWV (±10%). • Distribution of SH in the tropics are linked to the ENSO. • La Nina shows negative anomalies in UTWV at all longitudes in the tropical region. • El Nino show positive anomalies in UTWV at all longitudes in the tropical region. • Source region for these changes in UTWV is clearly visible as the Pacific region. [ABSTRACT FROM AUTHOR]

Using wave data from 1960 to 1990 from the European Centre for Medium-Range Weather Forecasts (ECMWF) reanalysis ERA-40 dataset and the ERA-5 reanalysis dataset (1990–2018), this paper presents a comprehensive study on the spatial and temporal variability of wind sea wave height (Hw), swell wave height (Hsw) and mixed significant wave height (H s) in the Pacific during the warm (El Niño) and cold (La Niña) ENSO phases. The main findings show that During DJF, the Hsw is dominated by strong winds and large waves from extratropical cyclones in the North Pacific, especially from 1960 to 1990. However, from 1990–2018 these maximum values extend into the subtropical crest of the Pacific Ocean and the southeast trade winds increase during La Niña. The annual cycle of Hw, Hsw and Hs for specific points located from the west center toward the east center along the equatorial Pacific for the analyzed decades show a strong transition in the locations of the maximum and minimum values during the year. In this sense, the eastern point is more highly influenced by the swell systems that flow from the northwest and southwest of the southern hemisphere associated with the intensification of winds during the occurrence of La Niña. It is therefore not possible to determine a single period of maximum and minimum values. During the decades of 1990–2018, the difference in swell wave height during La Niña compared to El Niño increased throughout the year compared to 1960–1990. During the 1960–1990 period, the maximum values were detected in JJA for both El Niño and La Niña in an area that extends from Perú and ends toward the eastern center of the Colombian Pacific Basin. • Scalar parameters were studied for sea, swell and mixed waves during ENSO in the Pacific Ocean. • Around latitude 12°N, the energetic values of Hw were detected in DJF and MAM during La Niña. • During La Niña the trade winds from Southern Hemisphere intensify in MAM and JJA. • The annual cycle for Hsw of virtual buoy 1 (center west) has a bimodal period DJF during ENSO. [ABSTRACT FROM AUTHOR]

Abstract: Seasonal rainfall in the Philippines is known to be modulated by ENSO phenomenon, with El Niño frequently contributing to reduced rainfall and drought while La Niña resulting in excessive rainfalls, floods and more intense typhoons. The alterations in rainfall patterns can have considerable feedback on solar radiation, air temperature, and soil moisture which can affect the ecosystem CO2 exchange. In this paper, we assessed the effects of the ENSO events (2008–mid 2010) on the seasonal climate conditions and determined how it affected the gross primary production (GPP), ecosystem respiration (Re), and net ecosystem production (NEP) of two contrasting rice environments: flooded and non-flooded. The 2008 dry season (DS) was under a La Niña event while the 2008 wet season (WS) was a neutral one with strong tropical cyclones associated during the wet season. The 2009DS was also La Niña while the 2009WS was El Niño; however, the northern part of the Philippines experienced strong tropical cyclones. The 2010DS was under an El Niño event. The La Niña in 2008DS resulted in about 15% lower solar radiation (SR), 0.3°C lower air temperature (T a) and 60% higher precipitation compared to the 28-year climate normal patterns. Both flooded and non-flooded rice fields had lower NEP in 2008 DS (164 and 14gCm−2, respectively) than in 2008 WS (295 and 82gCm−2, respectively) because the climate anomaly resulted in SR – driven decrease in GPP. The La Niña in 2009DS even resulted in 0.2°C lower air temperature and 40% more precipitation than the 2008DS La Niña. This cooler temperature resulted in lower Re in flooded rice fields while the higher precipitation resulted in higher GPP in non-flooded fields since the climate was favorable for the growth of the aerobic rice, the ratoon crops and the weeds. This climate anomaly benefitted both flooded and non-flooded rice fields by increasing NEP (351 and 218gCm−2, respectively). However, NEP decreased in 2009WS in both flooded and non-flooded rice fields (225 and 39gCm−2, respectively) due to the devastating effects of the strong tropical cyclones that hit the northern part of the Philippines. On the other hand, the El Niño event during 2010DS resulted in about 6% higher solar radiation, 0.4°C higher air temperature and 67% lower precipitation than the 28-year climate normal pattern. The NEP of flooded and non-flooded rice fields were closely similar at 187 and 174gCm−2, respectively. This climate anomaly resulted in T a – driven increase in Re, as well as vapor pressure deficit (VPD) – driven decrease in GPP in flooded rice fields. The GPP and Re in non-flooded rice fields were less sensitive to higher VPD and higher T a, respectively. It appears that the net ecosystem CO2 exchange in non-flooded rice field was less sensitive to an El Niño event. [Copyright &y& Elsevier]

Abstract: Based on size at maturity and standardized residuals from mantle length (ML)–total weight (TW) and mantle length–gonad weight (GW) relationships, this paper describes the interannual variability of the size at maturity (SM), somatic and reproductive investment of mature males and females of Dosidicus gigas during the spawning peak (October–March) for the period 1994–2006 in the Northern Humboldt Current Ecosystem (Peruvian waters). Significant changes occurred in the SM in females as well in males: before 2001 the average did not exceed 47cm ML, while from 2001 onwards the average MS varied between 62 and 96cm ML. The average SM was generally higher in females. There was a great individual variability of somatic and reproductive investment, being higher in large-sized mature squids. No relationship was found between SM and somatic condition. The presence of small-sized mature squids in good somatic condition under different scenarios of sea surface temperature (normal, warm or cold periods; El Niño and La Niña events) does not indicate a relationship between somatic condition and SST. The relationship between reproductive and somatic investment was variable and independent of the sex. It also varied among different years. This would indicate that females and males may respond differently under the same environmental conditions. Considering the relationship between fecundity and ML, mature females at larger sizes had a lower reproductive condition, but also a higher potential fecundity. Lower fertility potential for some small mature females is offset by greater investment in reproduction, particularly under adverse environmental conditions. The positive correlation between the abundance (CPUE) and SM shows that the biomass was greater in periods dominated by the presence of large-sized mature squid. [ABSTRACT FROM AUTHOR]

• MSDI is used to incorporates the meteorological and agricultural droughts across Iran. • 2007–08 and 2000 are the strongest and broadest droughts over the latest 38 years. • Pacific Ocean oscillations more controls droughts across Iran rather Atlantic Ocean. • Iran's extreme droughts resulted from strong La Nina coupled with cold PDO and positive NAO. Drought may affect more people than any other climate extremes worldwide, especially in (semi)arid climates such as Iran. In this paper, the empirical Multivariate Standardized Drought Index (MSDI) that incorporates the meteorological and agricultural drought conditions is first computed. The wavelet analysis is then used to identify teleconnections between ocean–atmosphere oscillations from Atlantic (AMO, AO, and NAO) and Pacific (ENSO, PDO, and PNA) oceans and Iran's drought at a highly dense network of regularly gridded points (2485) during 1979–2016. It is found that among the droughts of 1980, 1985–86, 1990–91, 1998–99, 2000, 2007–08, and 2010–11, both the 2007–08 and 2000 are the broadest and strongest across the country. Overall, those droughts that occurred in the 2000–2016 period (average MSDI = -1.14) were, on the whole, stronger than those happened over the latest 20 years of the 20th century (average MSDI = -0.77), reflecting the strengthening of the influence that ENSO has on the Middle East climate in the most recent decades. According to the wavelet coherence results, unlike the Atlantic-based oscillations that almost have an anti-correlation with droughts, there is a positive correlation between Pacific-based oscillations and Iran's drought. It is also identified that the severe historical droughts across the country were usually associated with a strong La Niña coupled with cold PDO and positive NAO phases in the latest 30 years. Overall, droughts in Iran tend to be substantially controlled by multiple interacting of climate indices since three-coupled indices have stronger coherence with drought than either two-coupled indices or single ones. A combination of the three indices of ENSO, PDO, and NAO has the strongest coherence with Iran's drought compared to all the other three- and two-coupled, and all single indices, indicating that integrated impact of climate indices can better capture hydroclimate teleconnections. These multiple interacting impacts from the different large-scale climate circulation patterns mark a significant step towards an improved prediction of severe droughts across Iran and can also be used for other parts of the world. [ABSTRACT FROM AUTHOR]

Estuarine freshwater discharge to the ocean and its oceanic transport represent a dynamic interaction between freshwater and ambient seawater. While a near-field estuarine freshwater mass propagation within 350 km away from estuary has been investigated via in-situ data and modeling, its far-field propagation remains unexplored. This paper, for the first time, explores the potential usage of Mekong estuarine-discharged freshwater mass in the ocean inferred from time-variable satellite gravimetry data (e.g. Gravity Recovery and Climate Experiment (GRACE)) to characterize spread pattern and transport paths, and propagation direction and time duration in the entire Sunda Shelf and southern South China Sea. Through a cross-correlation analysis, spatial distribution of maximum cross-correlation coefficient and time lag between in-situ Mekong estuarine runoff and gravimetry-inferred estuarine-discharged freshwater mass on the ocean surface were calculated. It was found that the gravimetry-inferred time lags were largely consistent with the freshwater ages derived by isotope analysis sampled from the campaign in September 2007. During 2005–2013, the long-term spatial patterns of the maximum cross-correlation coefficient generated over sliding five four-year time spans yielded eastward clockwise and westward counterclockwise freshwater transport pathways, in summer and winter respectively, in the Sunda Shelf and the southern South China Sea. The long-term spatial patterns of the time lag showed less than a month was required for the freshwater mass transporting in the northeast direction, while the time lag lengthened progressively from a month to four months, clockwise from the northeast to the southwest direction. This could be explained by the monthly ocean surface current averaged between 2005 and 2013, simulated by the Estimating the Circulation and Climate of the Ocean (ECCO) model. Using eight one-year time spans between 2005 and 2013, the short-term spatial patterns of the maximum cross-correlation coefficient and the time lag varied considerably, which were likely attributable to global climate variability. As usual, the western boundary current in the southwestern South China Sea should be enhanced in La Nina year. However, in the strong La Niña event during 2010–2011, the weakened southwest current in the western Sunda Shelf enabled faster southward freshwater mass transport, resulting in shorter time lag (within three months) than that of the long-term one. • Mekong freshwater mass transport in the sea is trackable by satellite gravimetry. • Gravimetry-inferred transport time duration is consistent with isotope-derived age. • Modeled oceanic mass transport explains a long-term seasonal freshwater movement. • Strong La Niña events accelerate mass transport in the southern South China Sea. [ABSTRACT FROM AUTHOR]

Abstract: This paper is part of a comprehensive review of the oceanography of the eastern tropical Pacific, the oceanic region centered on the eastern Pacific warm pool, but also including the equatorial cold tongue and equatorial current system, and summarizes what is known about oceanographic influences on seabirds and cetaceans there. The eastern tropical Pacific supports on the order of 50 species of seabirds and 30 species of cetaceans as regular residents; these include four endemic species, the world’s largest populations for several others, three endemic sub-species, and a multi-species community that is relatively unique to this ecosystem. Three of the meso-scale physical features of the region are particularly significant to seabirds and cetaceans: the Costa Rica Dome for blue whales and short-beaked common dolphins, the Equatorial Front for planktivorous seabirds, and the countercurrent thermocline ridge for flocking seabirds that associate with mixed-species schools of spotted and spinner dolphins and yellowfin tuna. A few qualitative studies of meso- to macro-scale distribution patterns have indicated that some seabirds and cetaceans have species-specific preferences for surface currents. More common are associations with distinct water masses; these relationships have been quantified for a number of species using several different analytical methods. The mechanisms underlying tropical species–habitat relationships are not well understood, in contrast to a number of higher-latitude systems. This may be due to the fact that physical variables have been used as proxies for prey abundance and distribution in species–habitat research in the eastern tropical Pacific. Though seasonal and interannual patterns tend to be complex, species–habitat relationships appear to remain relatively stable over time, and distribution patterns co-vary with patterns of preferred habitat for a number of species. The interactions between seasonal and interannual variation in oceanographic conditions with seasonal patterns in the biology of seabirds and cetaceans may account for some of the complexity in species–habitat relationship patterns. Little work has been done to investigate effects of El Niño-Southern Oscillation cycles on cetaceans, and results of the few studies focusing on oceanic seabirds are complex and not easy to interpret. Although much has been made of the detrimental effects of El Niño events on apex predators, more research is needed to understand the magnitude, and even direction, of these effects on seabirds and cetaceans in space and time. [Copyright &y& Elsevier]

Wave climate in the marginal seas and estuaries provide baseline information, risk assessments and essential insight into coastal design, structure and engineering projects. This paper investigates the Spatio-temporal trends in extreme Significant Wave Height (SWH) in the Niger Delta coastlines. For the study domain, European Centre for Medium-Range Weather Forecasts (ECMWF) global atmospheric reanalysis ERA-Interim and wave hindcast data covering 37 years (January 1, 1980–December 31, 2016), derived from WAVEWATCH III (WW3) model were used in the analysis. The largest 99th percentile approach was used to analyze extreme SWH values. Results showed near neutral and negative trends over the region. The trends are generally insignificant for the 100-year return period. The sharp variation in extreme SWH between 1998 and 2000 resulted from a strong El Nino and La Nina phenomenon, which is associated with the weakening and strengthening of the West-African Monsoon. • Several studies on wave climate variability have been published but not for the Niger Delta Coastlines. • This study investigates spatio-temporal trends in extreme Significant Wave Height (SWH) over the Niger Delta Coastlines. • The results are insignificant with no obvious trend in the 100-year return period for the 99th-percentile wave height. • Our results indicated sharp variation in extreme SWH between the years 1998 and 2000. • The extreme SWH is due to a strong El Nino and La Nina occurrences in association with the West-African Monsoon. [ABSTRACT FROM AUTHOR]

• The theory of mesoscale turbulence firstly applied for modeling of the equatorial Pacific Ocean currents. • Currents at the Earth's equator in the La Niño phase have a four-tier vertical structure. • El Niño is consequence of nutational oscillations and the gravity influence of the Moon, Sun and Jupiter. El Niño is a phenomenon of the catastrophic increase of surface temperature in the eastern part of the Pacific Ocean. It has a significant impact to weather of the American continent and western regions of the tropical Pacific, as well as on the weather and climate of entirely the Earth. Most important factors influencing El Niño are the wind, ocean currents and slope of the water surface (and temperature resulting from these factors) at the equator in the Pacific Ocean. The paper considers results of mathematical modeling of the equatorial Pacific Ocean currents in the El Niño and La Niña phases using the theory of mesoscale turbulence. This theory has been successfully tested in modeling of global circulation of atmosphere and ocean (Arsen'yev et al., 2010) and it has been able to calculate the ocean current changes at equator under changing external conditions. It is shown that the water currents at the equator have a four-tier vertical structure. The surface trade-wind current is located above the subsurface undercurrent, below which we observe the intermediate current, turning into the equatorial deep counter flow. When El Niño begins, the currents are rearranged, change signs and sometimes merge with each other. In the phase of maximum development of the phenomenon there is a two-tier structure: (1) surface current heading the American coast is underlain (below the depth of 440 m) by (2) deep equatorial current directed to the Indonesian coast. The theoretical calculations are compared with the physical observations of ocean currents in the El Niño and La Niña phases. The obtained results indicate that the proposed mathematical apparatus makes it possible to explain the set of physical observations in the Pacific Ocean. [ABSTRACT FROM AUTHOR]

The evolution of the mixed layer temperature anomalies in the Mozambique Channel is analysed using a mixed layer heat budget covering sub-seasonal to interannual time scales. Sub-seasonal variations in mixed layer temperature are largely dominated by surface heat fluxes, except along the southern coast of Mozambique and Madagascar, where both the advection and the residual terms become significant. The northern Channel is dominated by the mean flow while the southern Channel is modulated by both the mean and eddy terms. Minimum heat gain through advection is observed in the channel during January–February when the Northeast Madagascar current opposes the northwesterly monsoonal winds. During the 1997/98 El Niño/positive Indian Ocean dipole, extreme warming and coral bleaching events were noted in the northern Channel. Such warming was linked with the relaxation of local winds, positive heat gain from the atmosphere and the shedding of large anticyclonic eddies northwest of Madagascar, associated with the arrival of downwelling Rossby waves. By contrast, upwelling Rossby waves and large cyclonic eddies in the Channel occurred during the 1998–2001 protracted La Niña, but only the northern part of the Channel experienced significant negative anomalies in mixed layer temperature. While no coral bleaching hotspots were noted in the northern Channel in summer 1999/2000 due to negative anomalies in advection, marine heatwaves occurred in the southern Channel during that summer. Finally, the protracted 1998–2001 La Niña was the last time that substantial upwelling Rossby wave activity occurred in the tropical South Indian Ocean; recent La Niña events showed muted or weak upwelling Rossby wave activity, including the recent 2020–2022 protracted event. Post-2001 also occurs at the same time as a stronger warming trend in the southwest Indian Ocean region. • The mean flow dominates the northern Mozambique Channel, but both the mean and counteracting cyclonic eddies influence the southern Channel. • Channel warming (cooling) in 1997/98 (1999–2001) linked to anticyclonic (cyclonic) eddies, downwelling (upwelling) Rossby waves. • South Indian Ocean dominated by downwelling Rossby waves after 2001 (including La Niñas) with strong warming trend in the northern Channel. [ABSTRACT FROM AUTHOR]

The South Atlantic subtropical mode water (SASTMW) is a conspicuous volume of water formed during winter and early spring that occupies the mid-latitudes of the South Atlantic. Here, we aim to investigate the interannual variability of the SASTMW's volume in response to remote processes influenced by atmospheric teleconnection. We utilized the Simple Ocean Data Assimilation (SODA) ocean reanalysis to identify this particular mode water. The SASTMW's volume time series underwent a shift during the early aughts, with the frequency spectrum changing from broad and sparse interannual peaks during 1980–2001 to narrow and frequent peaks during 2002–2018, following the interdecadal shift of El Niño–Southern Oscillation (ENSO) that occurred in 1999. Hence, the influence of ENSO on SASTMW was evaluated for each of the two periods. From 1980 to 2001, in the western side of the basin, SASTMW's volume reached its peak 21 months after the occurrence of an El Niño, and after 43 months it became thinner. The opposite pattern occurred after a La Niña event, with stronger events having a greater impact on the SASTMW. In the 2002–2018 period, the largest correlations were observed in the eastern part of the basin, with significantly shorter lags of 6–20 months. • Subtropical mode water has an interannual variability shift at the early aughts. • Subtropical mode water responds differently to ENSO, during 1980–2001 and 2002–2021. • Subtropical mode water is more affected by intense ENSO events. [ABSTRACT FROM AUTHOR]

This paper presents a high-resolution analysis of dinoflagellate cyst groups (1959 to 2009), in the southern Gulf of California (GoC). We analyzed 100 samples of laminated sediments with an effective sampling resolution of ~7 months. Our primary goal is to clarify the relation between changes in these groups and the climate forcing defined by the El Niño Southern Oscillation (ENSO) and Pacific Decadal Oscillation (PDO) indices. Principal component analysis indicates three groups (A1, A2, and A3). A1 and A3 are mostly constituted by dinoflagellate cysts of heterotrophic taxa, while A2 is composed mainly of autotrophic taxa. Strong El Niño events decrease the contribution of all dinoflagellate cyst groups, while extreme La Niña events increase the contribution of the A2 and A3 groups. Also, the PDO modulates the marine productivity in the southern GoC, with cold phases increasing productivity, while the warm stages decrease productivity. As with climatic events in the southern GoC, autotrophic and heterotrophic taxa of dinoflagellate cysts respond clearly, when PDO and ENSO are in phase. Finally, dinoflagellate cyst concentrations in laminated sediments can be used regionally, as a chronostratigraphic tool in the last 50 years. • Annual record of dinoflagellate cyst assemblages from 1959 to 2009. • All taxa increase markedly (decrease) during strong Niña (Niño) and cold (warm) PDO. • Heterotrophic taxa have a periodicity of 10.91 years. • Control points: maxima 1975, and 2007, minima 1983, 1987, 1997 and 2003. [ABSTRACT FROM AUTHOR]

The link between tropical cyclone (TC) activity in the South China Sea (SCS) and global climate change is commonly debated and there is a clear need for long-term geological records of TC activity if we are to clarify this connection. Multi-millennial, high-resolution paleo-storm records from the SCS are rare in the region and this causes difficulties for those exploring potential climate drivers of TC variability over centennial to millennial timescales and reduces our ability to fully assess the risks associated with future TC activity. This paper presents an age-constrained, mud-dominated sedimentary sequence from a coastal lagoon on Hainan Island, China. Multiproxy analyses incorporating chronological, lithological, sedimentological, and geochemical evidence were used to infer storm deposits preserved within the sequence and to reconstruct a time series of storm activity in the SCS during the mid-to-late Holocene. This long sedimentary record shows that TCs were highly active over the periods 5500 to 3500 and 1700 to 0 cal yrs. BP, and these periods contrast with a relatively quiet period 3500–1700 cal yrs. BP. An apparent inverse correlation between TC reconstructions from the SCS and those from the Korean Peninsula and Japan implies an oscillating pattern across the SCS and western North Pacific (WNP) over centennial to millennial timescales. A comparison between the sedimentary and paleoclimatic records implies that the El Niño–Southern Oscillation was not the only mechanism responsible for typhoon variability over the past 7500 cal yrs. BP, suggesting that other factors such as the thermal state of the western Pacific warm pool likely also had a strong influence on both SCS and WNP TC variability. • Sedimentological evidence from Hainan Island was used to reconstruct typhoon activity in the SCS over the mid–late Holocene. • There exists a well-defined seesaw pattern in storm activity across the WNP basin during the study period. • Periods of increased (reduced) storm activity in the SCS typically coincide with La Niña (El Niño) periods and warm (cold) phases of the WPWP during the mid-late Holocene. [ABSTRACT FROM AUTHOR]

Tropical cyclones (TCs) are among the most important factors that influence the upper oceanic environment of the Western North Pacific (WNP). To better understand the effects of TCs on the changes in the physical and biological processes of the WNP, two regions with similar properties but different TC frequencies were studied. Unlike previous studies, the long-term effects of TCs on the biophysical properties of the WNP throughout the TC season were discussed. The biophysical properties of both regions during the TC season were compared using satellite-derived measurements and Argo float data during 2003–2017. During the TC season, short-term rapid enhancement of the wind during TC passages had a direct effect on the cooling of the sea surface temperature and the deepening of the mixed-layer depth. Moreover, surface nitrate concentrations in the TC-prone region were significantly higher than those in the region not heavily influenced by TCs. As a result, the mean surface chlorophyll-a (Chl -a) concentration in the region with a high TC frequency was significantly higher than that with a low TC frequency. The Chl -a concentrations also tended to be higher during the El Niño years because of more strong TC events in both regions, while they were generally lower during the La Niña years when there were fewer strong TCs. Based on a conservative estimate, new primary production in TC season caused by TCs in the region with a high TC frequency accounted for approximately 1–7% of the annual amount in this region during the study years. These findings suggest that the TCs play an important role in the enhancement of biological carbon fixation in parts of the WNP. • The biophysical properties of two marine areas with different tropical cyclone frequencies were compared. • Tropical cyclones produced large differences in Chl- a concentration, SST, and MLD in different marine areas. • Tropical cyclones significantly increased primary productivity in the WNP. [ABSTRACT FROM AUTHOR]

Abstract: A time-series sediment trap was operated from July 2003 to July 2008 at a station located in the 10°N thermocline ridge of the northeastern equatorial Pacific (10°30′N, 131°20′W), with the aim of understanding variations in natural background sinking-particle flux and the influence on such fluxes of ENSO (El Niño–Southern Oscillation). Each one of weak El Niño, moderate El Niño and moderate La Niña were observed during the monitoring period. During non-ENSO periods, total mass fluxes varied from 4.1 to 36.9mgm−2 d−1, with a distinct seasonal variation, ranging from an average flux of 14.0mgm−2 d−1 in the warm season (June–November) to 25.3mgm−2 d−1 in the cold season (December–May). This seasonal fluctuation was characterized by a distinct difference in CaCO3 flux between the two seasons. The enhanced particle fluxes during the cold season are attributed to the supply of nutrient-enriched subsurface water by wind-driven vertical mixing, supported by a simultaneous reduction in sea surface temperature and enhanced trade winds. The weak El Niño event occurred in the monitoring period had no recognizable effect on particle fluxes in the study area, but the moderate El Niño event was accompanied by a significant reduction in particle fluxes to 60% of the average background value in the warm season. In contrast, particle fluxes during the moderate La Niña increased to a maximum value of 129.9mgm−2 d−1, almost three times the average background value. Organic carbon and biogenic silica fluxes were most sensitive to the El Niño and La Niña conditions. The observed variations of particle fluxes are synchronized with those of chlorophyll-a, suggesting primary productivity for the main cause of flux change. The present data indicate that marked seasonal variability in background fluxes commonly exceeds the variability associated with ENSO and post-ENSO signals, which should be taken into account when evaluating the influence of ENSO on sinking particle fluxes in the 10°N thermocline ridge area. [Copyright &y& Elsevier]

Abstract: A biogeochemical model of the tropical Pacific has been used to assess the impact of interannual variability in a western Pacific iron source on the iron-limited ecosystem of the central and eastern Pacific during the 1997–1998 El Niño. A reference simulation and two simulations with an iron source in the western Pacific have been performed. The two “source” simulations differed only in the temporal variability of the iron source. In the variable source simulation, the iron concentration in the source region was proportional to the velocity of the New Guinea Coastal Undercurrent (NGCUC). In the constant source simulation, the same time-averaged concentration of iron was imposed with no temporal variability. The variable source was designed to mimic variations of iron flux from the northeast slope of New Guinea to the NGCUC due to modulation of sedimentary iron resuspension as previously hypothesized. Through the comparison of these simulations, it appeared that: (i) an iron source in the NGCUC, regardless of its source variability, increases biomass in the eastern equatorial Pacific because of the greater eastward iron flux by the Equatorial Undercurrent and (ii) a variable NGCUC iron source does not change the temporal variability of eastern Pacific chlorophyll, and in particular the timing and intensity of the June 1998 bloom. To explain eastern Pacific biological variability, local rather than remote processes are needed, such as wind-driven upwelling, the local depth of the thermocline, tropical instability waves and biological processes such as high grazing pressure. Therefore, while the western Pacific sources of dissolved iron are important in our model to sustain annually integrated equatorial Pacific production, they are unlikely to strongly constrain the timing of blooms in the central and eastern Pacific such as during the 1998 La Niña. [Copyright &y& Elsevier]

Abstract: The water masses of the central and western equatorial Pacific can be divided into two parts: the Western Pacific Warm Pool (WPWP) and the Equatorial Upwelling Region (EUR). The behavior of the WPWP plays a significant role in global climate changes such as the El Niño-Southern Oscillation (ENSO), and it drastically modifies the oceanographic conditions in the area every few years. It is important to evaluate changes in time-series diatom fluxes during both the El Niño and the La Niña events. As a part of the Global Carbon Cycle and Related Mapping based on Satellite Imagery (GCMAPS) Program, time-series sediment trap moorings were deployed and recovered along the Equator at seven stations (Sites MT1–MT7) during five R/V Mirai cruises in the central and western Pacific during January 1999–January 2003. The entire length of this study is divided into two phases depending on the oceanographic conditions: the La Niña event (1999 and 2000); and the El Niño event (2002). Site MT3 was located in the WPWP and Sites MT5–MT7 were in the EUR. Annual means of total diatom fluxes increased towards the east in each year. The fluxes observed at Sites MT4–MT6 decreased from the La Niña event to the El Niño event. However, the fluxes observed at Site MT3 in 2001 and 2002 were higher than those in 2000. Total diatom fluxes showed different seasonal patterns at all sites. The diatom assemblages in the WPWP differed from those of the EUR. Pennate diatoms (e.g., Nitzschia bicapitata, Thalassionema nitzschioides) dominated in the WPWP, while the relative abundances of centric diatoms (e.g., Rhizosolenia bergonii, Azpeitia spp., Thalassiosira spp.) were higher than those of pennate diatoms in the EUR. The diatom fluxes during the La Niña event reflected seasonal oscillation of the WPWP in spatial extent. At Site MT3 during El Niño, terrestrial materials appeared to have been transported by subsurface currents, which might be a secondary influence on total diatom fluxes. The spatial extent of the WPWP reached Site MT7 in 2002, when total diatom fluxes decreased in the sediment traps located in the eastern region including Site MT7. Therefore, we conclude that the relationships between the ENSO and diatoms fluxes in the western and central equatorial Pacific can be explained by the geographic (west–east) expansion or contraction of the WPWP. [Copyright &y& Elsevier]

The distribution and transport of paralarvae of the complex Sthenoteuthis oualaniensis - Dosidicus gigas (SD complex, Cephalopoda: Ommastrephidae) in the tropical-subtropical convergence off Mexico were analyzed under contrasting interannual environmental conditions. Two El Niño years were sampled (2010 and 2016), in which the SST were up to 3 °C above the average throughout the study area, while during La Niña year (2012) the SST anomalies were up to 2 °C below the average. During El Niño years, a relative shallow thermocline (<60 m depth) was detected around Cabo Corrientes, where the paralarvae were found with mean abundance of 2 org 1000 m−3. During La Niña condition, a shallower thermocline was detected in the entrance of the Gulf of California (~20 m depth) and the paralarvae abundance rose to 84 org 1000 m−3 with high frequency of occurrence. In both El Niño and La Niña conditions the paralarvae were mainly found in the strongly stratified waters (>80 cycles h−1). In addition, a simple dispersion Lagrangian model based on observed satellite geostrophic currents, suggested association of the SD complex paralarvae with mesoscale structures, in which the eggs and hatched paralarvae had an appropriate habitat for a nursery, retaining the paralarvae until their recruitment in a ~100 km radius. But during warm extreme events, with less mesoscale activity, the paralarvae could be transported as far as 500 km southeast of the spawning zone. Even though the interannual ENSO conditions modulate the magnitude of the paralarvae abundance, the shallow and well developed thermocline could help paralarvae to increase their survival chances, while mesoscale activity retains them near the productive coastal waters. • ENSO phases modulate Sthenoteuthis-Dosidicus complex paralarval abundance. • Mesoscale eddies retain paralarvae near coastal waters. • Lack of mesoscale eddy circulation leads to high paralarval dispersion rate. [ABSTRACT FROM AUTHOR]