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Recent observations in the eastern tropical South Pacific (ETSP) demonstrated the key role of meso- and submesoscale processes (e.g. eddies) in shaping its hydrographic and biogeochemical properties. Off Peru, elevated primary production from coastal upwelling in combination with sluggish ventilation of subsurface waters fuels a prominent oxygen minimum zone (OMZ). Given that nitrous oxide (N2O) production/consumption processes on the water column are sensitive to oxygen (O2) concentrations, the ETSP is a region of particular interest to investigate its source-sink dynamics. To date, no detailed surveys linking mesoscale processes and N2O distributions as well as their relevance to nitrogen (N) cycling are available. In this study, we present the first measurements of N2O across three mesoscale eddies (two mode water or anticyclonic and one cyclonic) which were identified, tracked and sampled during two surveys carried out in the ETSP in November-December 2012. A "two peak" structure was observed for N2O, wherein the two maxima coincide with the upper and lower boundaries of the OMZ, indicating active nitrification and partial denitrification. This was further supported by the abundances of the key gene for nitrification amoA and the gene marker for N2O production during denitrification, nirS. Conversely, we found strong N2O depletion in the core of the OMZ (O2 < 5 μmol L-1) to be consistent with nitrite (NO2-) accumulation and low levels of nitrate (NO3-1), thus suggesting active denitrification. N2O depletion within the OMZ's core was substantially higher in the center of mode water eddies, supporting the view that eddy activity enhances N-loss processes off Peru, in particular near the shelf break where nutrient-rich, productive waters from upwelling are trapped before being transported offshore. Analysis of eddies during their propagation towards the open ocean showed that, in general, "aging" of mesoscale eddies tends to decrease N2O concentrations through the water column in response to reduced supply of material to fuel N-loss, although hydrographic variability might also significantly impact the pace of the production/consumption pathways for N2O. Our results demonstrate the relevance of mode water eddies for N2O distribution, thereby improving our understanding of the N-cycling processes, which are of crucial importance in times of climate change and ocean deoxygenation. [ABSTRACT FROM AUTHOR]

Changes in Southern Ocean (SO) phytoplankton distributions with future warming have the potential to significantly alter nutrient and carbon cycles as well as higher trophic level productivity both locally and throughout the global ocean. Here we investigate the response of SO phytoplankton productivity and biomass to 21st century climate change across the CMIP5 Earth System Model suite. The models predict a zonallybanded pattern of phytoplankton abundance and production changes within 4 regions: the subtropical (∼ 30° S to 40° S), transitional (∼ 40° S to 50° S), subpolar (∼ 50° S to 65° S) and Antarctic (south of ∼ 65° S) bands. We find that shifts in bottom-up variables (nitrate, iron, and light availability) drive changes in phytoplankton abundance and production on not only interannual, but also decadal and 100-year timescales: the timescales most relevant to climate change. Spatial patterns in the modeled mechanisms driving these biomass trends qualitatively agree with recent observations, though longer-term records are needed to separate the effects of climate change from those of interannual variability. Because much past observational work has focused on understanding the effects of the Southern Annular Mode (SAM) on biology, future work should attempt to quantify the precise influence of an increasingly positive SAM on SO biology within the CMIP5 models. Continued long-term in-situ and satellite measurements of SO biology are clearly needed to confirm model findings. [ABSTRACT FROM AUTHOR]

This paper analyses a series of high-quality continuous records from southeastern Africa to study the spatiotemporal patterning of Holocene hydroclimatic anomalies in the region. Results indicate dominant frequencies of variability at millennial time scales, and a series of anomalies broadly common to all records. Of particular interest, data from the southern Cape coast exhibit periods of wetter/drier conditions that are out of phase with the sites less than 150 km away in the adjacent interior, but in phase with sites in tropical regions over 1000 km to the northeast. To explain such spatial patterns and gradients, we propose that the Agulhas Current may be a critical vector by which tropical climatic signals are propagated along the littoral zone, exerting a dominant, highly localized influence on near-coastal environmental conditions. Limitations in the data available do not allow for a detailed examination of the climatic dynamics related to these phenomena, but this paper highlights a series of avenues for future research to clarify the spatial extent and stability of the patterns observed. [ABSTRACT FROM AUTHOR]

Climatic and anthropogenic changes cause the deprivation of distinct ecosystems in Costa Rica, transforming climatic, ecological, and geomorphic conditions. The high tropical biodiversity of Costa Rica and the tropics is suitable to improve the understanding of hydrogeomorphic process dynamics and to produce baseline data on past disasters in scarce-data regions. The principal motivation to connect natural hazards and dendrochronology on tropics is the desire to create methods that can reduce its exposure and vulnerability. The principal research aim of this study is to give reference data that can improve the understanding of hydrogeomorphic processes and to explore the potential of tropical trees in dendrochronological applications. This paper combines remote sensing, meteorological assessments, and dendrochronology analyses, hydraulic modelling, and risk assessments. This innovative research describes the reduced understanding in treering analysis in Costa Rica related with past disasters and their linkage to climate. This study will likely contribute to the implementation of new methodologies in disaster risk research, and it will promote future adaptation strategies in the most biodiverse region of the world. [ABSTRACT FROM AUTHOR]

Cattle ranchers and dairy farmers operating throughout many tropical regions are experiencing major challenges associated with climate change such as higher incidence of heat stress and drought. These effects can result in reduced productivity of rangeland, shortage of nutritional feed, increased heat stress on animals, and high energy costs for cooling. High temperatures and resultant heat stress reduce animal productivity and increase the proliferation and survival of parasites and disease pathogens. Warming reduces the ability of dairy cattle to produce milk and gain weight and can also lower conception rates. This paper reviews research from the Caribbean on heat tolerant traits in bovine and presents evidence that introducing a “slick hair” gene into Holstein cows by crossbreeding with Senepols may increase thermo-tolerance and productivity. As in other parts of the tropics, principal cattle breeds in Puerto Rico and the US Virgin Islands have been largely introduced from temperate regions. Research indicates these animals may be poorly adapted to rising temperatures, leaving them increasingly vulnerable to chronic heat stress and reduced productivity. Adaptive practices have been developed in breeding and pasture management programs including selection for more heat-resistant genotypes, silvopasturing and crop diversification in forage production, and optimizing facilities and practices to reduce heat stress. Given the nature of climate vulnerability, an integrated approach to adaptation will likely have the greatest success in reducing future risk for producers. [ABSTRACT FROM AUTHOR]

As is true of many tropical regions, northeastern Puerto Rico is an ecologically sensitive area with biological life that is highly elevation dependent on precipitation and temperature. Climate change has the potential to increase the risk of losing endemic species and habitats. Consequently, it is important to explore the pattern of trends in precipitation and temperature along an elevation gradient. Statistical derivatives of a frequently sampled dataset of precipitation and temperature at 20 sites along an elevation gradient of 1000 m in northeastern Puerto Rico were examined for trends from 2001 to 2013 with nonparametric methods accounting for annual periodic variations such as yearly weather cycles. Overall daily precipitation had an increasing trend of around 0.1 mm day−1 yr−1. The driest months of the annual dry, early, and late rainfall seasons showed a small increasing trend in the precipitation (around 0.1 mm day−1 yr−1). There was strong evidence that precipitation in the driest months of each rainfall season increased faster at higher elevations (0.02 mm day−1 more increase for 100-m elevation gain) and some evidence for the same pattern in precipitation in all months of the year but at half the rate. Temperature had a positive trend in the daily minimum (around 0.02°C yr−1) and a negative trend in the daily maximum whose size is likely an order of magnitude larger than the size of the daily minimum trend. Physical mechanisms behind the trends may be related to climate change; longer-term studies will need to be undertaken in order to assess the future climatic trajectory of tropical forests. [ABSTRACT FROM AUTHOR]

The present study investigates the impact of northern mid-winter major stratospheric warming on tropical convection over the Indian region by examining the five Mid-winter Major Stratospheric Warming (MSW) events 2003/04, 2005/06, 2008/09, 2012/13, and 2018/19. The dynamical variables like temperature, wind components, and Outgoing Longwave Radiation are utilized from ECMWF ERA-Interim Reanalysis and NOAA site. Eliassen Palm (E-P) flux is used to visualize the upward and equator-ward propagation of extratropical Planetary Waves (PWs) from the lower atmosphere and their reach to the tropical region. The dominance of extratropical PW forcing from high to low latitudes is seen in all mid-winter cases. Further, the transfer of PW energy to low latitudes modifies the convection pattern over the Indian region. The author found depleted convection in the latitude band -15-20oN for the MSW 2003/04 and 2018/19, with frequent changes seen during MSW 2012/13 and 2005/06. On the other hand, the MSW 2008/09 show enhanced convection in the entire latitude band 20oS-20oN. This work suggests that the modification of OLR depends on the PW energy, onset time, peak temperature, and wind-reversed state during MSW. [ABSTRACT FROM AUTHOR]

In many countries, the natural phenomenon of lightning has been studied taking an account climatic and physiographic conditions. The atmospheric discharges are responsible for the death of more than 6000 people per year in the world. Colombia is located in the intertropical convergence zone and it has a geography characterized by plains and long mountain ranges. These conditions make Colombia located in the region with the highest lightning activity in the world increasing, increasing the number of deaths and injuries by this phenomenon, especially in rural zones. This paper presents a study about the total number of deaths and the mortality rate by lightnings for the period between 1997 and 2014. The information about deaths by lightning was taken from the statistics of the National Administrative Department of Statistics (Departamento Administrativo Nacional de Estadísticas - DANE). The obtained results are synthesized for all country and are discriminated by departments and natural subregions. In this way, the mortality rate obtained for Colombia was 1.51 per million people per year. Likewise, Vichada was the department with the highest mortality rate (7.85), while Popayan Plateau was the natural subregion with the highest number of deaths per million people per year with 8.62. [ABSTRACT FROM AUTHOR]

This paper uses new, high resolution satellite-derived data to explore recent cross-national differences in expanding tree cover. Increases in tree cover have concentrated in nations with recent histories of extensive deforestation, humid climates, high crop yields, and small numbers of farm workers. The associations of expanded tree cover with high yields for cereal crops and small populations of cultivators suggests a dynamic, sometimes referred to as a forest transition, in which urbanization and industrialization promote a long-term expansion in tree cover on certain types of land. The association of tree cover gains with tree cover losses and humid climates suggests a second dynamic, a churning, treadmill-like production of wood products from lands subjected to recurring harvests of wood products followed by tree cover gains in the recently harvested areas. The forest transition dynamic suggests that many smallholders would allow tree cover to expand on their lands if payments for environmental services were available. The salience of the treadmill dynamic of tree cover losses followed by tree cover gains underscores the importance of questions about the implications of commercial tree monocultures for biodiversity, carbon sequestration, and social justice. [ABSTRACT FROM AUTHOR]

This paper reports the nightglow observations of OI 630.0nm emissions, made by using all sky imager operating at low latitude station Kolhapur (16.8°N, 74.2°E and dip lat. 10.6°N) during high sunspot number years of 24th solar cycle. The images are analyzed to study the nocturnal, seasonal and solar activity dependence occurrence of plasma bubbles. We observed EPBs in images regularly during a limited period 19:30 to 02:30LT and reach maximum probability of occurrence at 22:30LT. The observation pattern of EPBs shows nearly no occurrence during the month of May and it maximizes during the period October–April. The equinox and solstice seasonal variations in the occurrence of plasma bubbles show nearly equal and large differences, respectively, between years of 2010–11 and 2011–12. [ABSTRACT FROM AUTHOR]

The general features of occurrence of an additional layer on the bottom side of F region, referred to as F0.5 layer in the pre noon period, over the magnetic equatorial location of Trivandrum (8.5°N; 77°E; dip lat of 0.5°N) in India during the period from 2004 to 2007 are presented using ionosonde observations. The F0.5 layer has a June (northern summer) solsticial maximum probability of occurrence with secondary maxima during December (northern winter) solstice. The seasonal as well as the day-to-day variability in the occurrence of F0.5 layer as mentioned in this paper seems to be a result of the variations in the amplitude and phases of the tides and gravity waves, and inventory of the metallic ions of meteoric origin. This study brings out an important manifestation of morning time F layer base region dynamics. [ABSTRACT FROM AUTHOR]

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Fruit abscission facilitates the optimal conditions and timing of seed dispersal. Environmental regulation of tropical fruit abscission has received little attention, even though climate change may have its strongest impacts in tropical regions. In this study, oil palm fruit abscission was monitored during multiple years in the Benin Republic to take advantage of the climatic seasonality and the continuous fruit production by this species. An innovative multivariable statistical method was used to identify the best predictors of fruit abscission among a set of climate and ecophysiological variables, and the stage of inflorescence and fruit bunch development when the variables are perceived. The effects of climate scenarios on fruit abscission were then predicted based on the calibrated model. We found complex regulation takes place at specific stages of inflorescence and bunch development, even long before the fruit abscission zone is competent to execute abscission. Among the predictors selected, temperature variations during inflorescence and fruit bunch development are major determinants of the fruit abscission process. Furthermore, the timing of ripe fruit drop is determined by temperature in combination with the trophic status. Finally, climate simulations revealed that the abscission process is robust and is more affected by seasonal variations than by extreme scenarios. Our investigations highlighted the central function of the abscission zone as the sensor of environmental signals during reproductive development. Coupling ecophysiological and statistical modeling was an efficient approach to disentangle this complex environmental regulation. [ABSTRACT FROM AUTHOR]

The width of the tropical Hadley circulation (HC) has garnered intense interest in recent decades, owing to the emerging evidence for its expansion in observations and models and to the anticipated impacts on surface climate in its descending branches. To better clarify the causes and impacts of tropical widening, this work generalizes the zonal mean HC to the regional level by defining meridional overturning cells (RC) using the horizontally divergent wind. The edges of the RC are more closely connected to surface hydroclimate than more traditional metrics of regional tropical width (such as the sea level pressure ridge) or even than the zonal mean HC. Simulations reveal a robust weakening of the RC in response to greenhouse gas increases, along with a widening of the RC in some regions. For example, simulated widening of the zonal mean HC in the Southern Hemisphere appears to arise in large part from regional overturning anomalies over the Eastern Pacific, where there is no clear RC. Unforced interannual variability in the position of the zonal mean HC edge is associated with a more general regional widening. These distinct regional signatures suggest that the RCs may be well suited for the attribution of observed circulation trends. The spatial pattern of regional meridional overturning trends in reanalyses corresponds more closely to the pattern associated with unforced interannual variability than to the pattern associated with CO2 forcing, suggesting a large contribution of natural variability to the recent observed tropical widening trends. Plain Language Summary: The large‐scale tropical wind patterns responsible for the dry desert belts on either side of the tropics appear to be expanding. Most explanations for this widening are based on the tropics as a whole and do little to address whether the subtropics are widening from one region to the next. This study extends the definition of tropical width—specifically the Hadley cell edge—to the regional level. The regional tropical edge lines up with deserts better than another, more conventional regional indicator. The observed pattern of tropical widening more closely resembles natural changes than human‐caused widening during much of the year. Key Points: The local tropical edge diagnostic follows spatial hydroclimate variations more closely than does the subtropical ridgeObserved widening, forced widening, and interannual variations each have their own regional signatureThe pattern of observed regional widening more closely matches unforced interannual variations than forced regional widening [ABSTRACT FROM AUTHOR]

Remarkable interannual variability in the thermocline depth in the southern tropical Indian Ocean (STIO) is analyzed using reanalysis data during 1980–2017. Previous studies have shown that the El Niño‐Southern Oscillation (ENSO) has a significant relationship with thermocline depth anomalies in this region. We find that both the eastern‐Pacific (EP) and central‐Pacific (CP) ENSO have important impacts on the STIO thermocline variation. The positive and negative phases of thermocline anomalies in the STIO are induced by asymmetric forcings from the two phases of ENSO. EP‐El Niño and CP‐La Niña events tend to induce larger thermocline depth anomalies in the STIO. Equatorial westerly and STIO anticyclonic winds during EP‐El Niño events can induce downwelling Rossby waves that extend far toward the western Indian Ocean, which dominates the westward propagation of thermocline anomalies, while upwelling Rossby waves during CP‐La Niña events cannot extend that far west. Plain Language Summary: Despite more researches mentioned about the global warming slowdown, the extreme events like the El Niño‐South Oscillation (ENSO) happen more frequently in the real world. Previous studies proved that the ocean thermocline depth in the southern tropical Indian Ocean (STIO) is influenced by different ENSO events (El Niño and La Niña), and the ENSO events have been divided as the eastern‐Pacific (EP) and central‐Pacific (CP) El Niño/La Niña based on different locations of the maximum sea surface temperature anomalies centers during the past decades. In this study, we present the relationships between the STIO thermocline depth and EP/CP El Niño/La Niña in this complex circumstance. We find that forcings from El Niño and La Niña are asymmetric, and the EP‐El Niño and CP‐La Niña events tend to induce larger thermocline variations. Considering these two different ENSO events, as mentioned above, happen more frequently, the variation of the STIO thermocline might be much greater in the future. Key Points: Both EP and CP ENSO events have important impacts on the thermocline variability in the STIOForcings from El Niño and La Niña events are asymmetric with the EP‐El Niño (CP‐La Niña) inducing a greater deepening (shoaling) thermoclineEP‐El Niño events induce Rossby waves extending far toward the western Indian Ocean, which induced by CP‐La Niña cannot extend far west [ABSTRACT FROM AUTHOR]

Two outlying projections of the East African Long Rains suggest the seasonal rainfall may double by the late 21st century. Previous work has linked these extremes—found in the IPSL‐CM5A model—to an exceptional March to May warming of the southern Indian Ocean. The current study shows a strong feedback between sea surface temperature (SST) increases and reduced low‐level cloud cover (with similar behavior in other southern subtropical oceans). An observational constraint is developed by demonstrating a correlation across 28 models between the strength of present‐day interannual SST‐cloud sensitivity and future SST response. Verification of the present‐day sensitivity finds that IPSL‐CM5A's feedbacks are very likely overestimated. It is therefore suggested its projections should be discounted for the March to May southern Indian Ocean and East African Long Rains. This narrows the CMIP5 plausible range of Long Rains totals by a third. Plain Language Summary: Predictions of seasonal mean rainfall for the middle to late 21st century vary substantially between climate models. This is problematic for those making policy and infrastructure decisions that must remain resilient to a range of possible futures. Consequently, climate scientists are often requested to identify the most and least reliable models, in order to narrow this range. This study focuses on the Long Rains of East Africa, for which one unusual model suggests a doubling of seasonal totals by the late 21st century. The primary physical causes of this exceptional prediction are examined and then linked to the strength of two‐way interactions between clouds and surface temperatures in the southern Indian Ocean for a comparison with observational data. It is concluded that this model's extreme predictions for both the southern Indian Ocean and the East African Long Rains are likely unreliable. The plausible range of the full ensemble of Long Rains predictions is narrowed by about a third. Key Points: Outlying projections of the East African Long Rains suggest seasonal totals may double; judging their reliability is critical for usersThese outliers exhibit an unusually strong feedback between clouds and surface warming in the southern subtropical Indian OceanAn observational constraint founded on interannual surface cloud sensitivities reduces projection uncertainty of the Long Rains by a third [ABSTRACT FROM AUTHOR]

Changes in microclimate due to urban morphology tend to directly affect outdoor thermal comfort, thereby influencing people's behavior. In order to investigate that, this study analyzed preferences for specific resting areas within an urban square surrounded by high-rise buildings in a subtropical location. In order to understand behavioral adaptations as regards sunlight availability (direct or reflected) or shaded situations (partly, fully) in resting areas, the analysis was conducted according to an observational method during the four seasons of 2016. Two high-definition cameras with time-lapse function were positioned at vantage points facing distinct benches, shooting at intervals of 1.5 min between scenes. Altogether, 86,561 scenes were analyzed. As a thermal comfort parameter, the outdoor thermal comfort index 'PET' (physiological equivalent temperature) was used, by post-processing meteorological data from the local meteorological station. The availability of situations (sun-lit, shaded-partly or fully, reflected sunlight) in each frame and per bench and the preference of visitors for such areas were considered in the analysis. During winter, there was a prevalence of shaded situations, mostly due to adjacent buildings. In summer, the most common condition was partly shaded by trees. The choice for a given resting condition was found to be closely related to PET index values and thermal comfort/stress classes and less so to seasonal changes. [ABSTRACT FROM AUTHOR]

The use of Beauveria bassiana in biological control of agricultural pests is mainly hampered by environmental factors, such as elevated temperatures and low humidity. These limitations, further amplified in a global warming scenario, could nullify biological control strategies based on this fungus. The identification of thermotolerant B. bassiana isolates represents a possible strategy to overcome this problem. In this study, in order to maximize the probability in the isolation of thermotolerant B. bassiana, soil samples and infected insects were collected in warm areas of Syria. The obtained fungal isolates were tested for different biological parameters (i.e., growth rate, sporulation and spore germination) at growing temperatures ranging from 20°C to 35°C. Among these isolates (eight from insects and 11 from soil samples), the five with the highest growth rate, spore production and germination at 30°C were tested for their entomopathogenicity through in vivo assays on Ephestia kuehniella larvae. Insect mortality induced by the five isolates ranged from 31% to 100%. Two isolates, one from Phyllognathus excavatus and one from soil, caused 50% of the larval mortality in less than four days, reaching values exceeding 92% in ten days. These two isolates were molecularly identified as B. bassiana sensu stricto by using three markers (i.e., ITS, Bloc and EF1-α). Considering these promising results, further studies are ongoing, testing their efficiency in field conditions as control agents for agricultural insect pests in Mediterranean and Subtropical regions. [ABSTRACT FROM AUTHOR]

Subtropical stationary waves may act as an important bridge connecting regional hydrological extremes with global warming. Observations show that the boreal summer stationary-wave amplitude (SWA) had a significantly positive trend during 1979–2013. Here, we investigate the past and future responses of SWA to increasing climate forcing using 31 CMIP5 GCMs. Twenty-four out of 31 models display a consistent increase in climatological-mean SWA in response to warming. To assess the detectability of a trend in SWA, we compared half-century trends between preindustrial control (PiControl), historical, and RCP8.5 simulations. The probability distribution of the normalized SWA trend obtained through bootstrapping shows neither positive nor negative tendencies of SWA trend in PiControl simulations. Twenty-two of 31 historical simulations exhibit a positive SWA trend. The SWA trends in 26 of 31 RCP8.5 simulations are positive. The finding supports the hypothesis that the positive SWA trend is at least partially driven by increasing external forcing. The linear regression of interannual variability in hydrological extreme frequency on SWA suggests that high SWA is related to increased heavy-rainfall-day frequency over South Asia, the Indochinese Peninsula, and southern China (SA-EA), and to increased dry-spell-day frequency over the northwestern and central United States (NUS) and the southern United States and Mexico (SUS-MEX). The projected amplification of SWA, combined with the relationships between SWA and number of hydrological extremes, may partially explain projected increases in the number of dry spells over NUS and SUS-MEX and the number of heavy-rainfall days over SA-EA. [ABSTRACT FROM AUTHOR]

Abstract: Collaboration can improve conservation initiatives through increases in article impact and by building scientific understating required for conservation practice. We investigated temporal trends in collaboration in the tropical ecology and conservation literature by examining patterns of authorship for 2271 articles published from 2000 to 2016 in Biotropica and the Journal of Tropical Ecology. Consistent with trends in other studies and scientific disciplines, we found that the number of authors per article increased from 2.6 in 2000 to 4.2 in 2015 using a generalized linear model (glm). We modeled changes in multinational collaboration in articles using a glm and found that the mean number of author‐affiliated countries increased from 1.3 (±0.6 SD) to 1.7 (±0.8 SD) over time and that increases were best explained by the number of authors per article. The proportion of authors based in tropical countries increased, but the probability of tropical–extratropical collaboration did not and was best explained solely by the number of authors per article. Overall, our analyses suggest that only certain types of collaboration are increasing and that these increases coincide with a general increase in the number of authors per article. Such changes in author numbers and collaboration could be the result of increased data sharing, changes in the scope of research questions, changes in authorship criteria, or scientific migration. We encourage tropical conservation scientists continue to build collaborative ties, particularly with researchers based in underrepresented tropical countries, to ensure that tropical ecology and conservation remains inclusive and effective. [ABSTRACT FROM AUTHOR]

Based on reanalysis data, we find that the Indian Ocean Dipole (IOD) plays an important role in the variability of wave climate in the equatorial Northern Indian Ocean (NIO). Significant wave height (SWH) in the equatorial NIO, especially over the waters southeast to Sri Lanka, exhibits strong interannual variations. SWH anomalies in the waters southeast to Sri Lanka correlate well with dipole mode index (DMI) during both summer and autumn. Negative SWH anomalies occur over the oceanic area southeast to Sri Lanka during positive IOD events and vary with different types of IOD. During positive prolonged (unseasonable) IOD, the SWH anomalies are the strongest in autumn (summer); while during positive normal IOD, the SWH anomalies are weak in both summer and autumn. Strong easterly wind anomalies over the southeast oceanic area of Sri Lanka during positive IOD events weaken the original equatorial westerly wind stress, which leads to the decrease in wind-sea waves. The longer wave period during positive IOD events further confirms less wind-sea waves. The SWH anomaly pattern during negative IOD events is nearly opposite to that during positive IOD events. [ABSTRACT FROM AUTHOR]

Arctic geoengineering wherein sunlight absorption is reduced only in the Arctic has been suggested as a remedial measure to counteract the on-going rapid climate change in the Arctic. Several modeling studies have shown that Arctic geoengineering can minimize Arctic warming but will shift the Inter-tropical Convergence Zone (ITCZ) southward, unless offset by comparable geoengineering in the Southern Hemisphere. In this study, we investigate and quantify the implications of this ITCZ shift due to Arctic geoengineering for the global monsoon regions using the Community Atmosphere Model version 4 coupled to a slab ocean model. A doubling of CO2 from pre-industrial levels leads to a warming of ~6 K in the Arctic region and precipitation in the monsoon regions increases by up to ~15%. In our Arctic geoengineering simulation which illustrates a plausible latitudinal distribution of the reduction in sunlight, an addition of sulfate aerosols (11 Mt) in the Arctic stratosphere nearly offsets the Arctic warming due to CO2 doubling but this shifts the ITCZ southward by ~1.5° relative to the pre-industrial climate. The combined effect from this shift and the residual CO2-induced climate change in the tropics is a decrease/increase in annual mean precipitation in the Northern Hemisphere/Southern Hemisphere monsoon regions by up to −12/+17%. Polar geoengineering where sulfate aerosols are prescribed in both the Arctic (10 Mt) and Antarctic (8 Mt) nearly offsets the ITCZ shift due to Arctic geoengineering, but there is still a residual precipitation increase (up to 7%) in most monsoon regions associated with the residual CO2 induced warming in the tropics. The ITCZ shift due to our Global geoengineering simulation, where aerosols (20 Mt) are prescribed uniformly around the globe, is much smaller and the precipitation changes in most monsoon regions are within ±2% as the residual CO2-induced warming in the tropics is also much less than in Arctic and Polar geoengineering. Further, global geoengineering nearly offsets the Arctic warming. Based on our results we infer that Arctic geoengineering leads to ITCZ shift and leaves residual CO2 induced warming in the tropics resulting in substantial precipitation decreases (increases) in the Northern (Southern) hemisphere monsoon regions. [ABSTRACT FROM AUTHOR]

Precipitation and column water vapor data from 13 CMIP5 models and observational datasets are used to analyze atmospheric moisture recycling rate from 1988 to 2008. The comparisons between observations and model simulations suggest that most CMIP5 models capture two main characteristics of the recycling rate: 1) long-term decreasing trend of the global-average maritime recycling rate (atmospheric recycling rate over ocean within 60°S–60°N) and 2) dominant spatial patterns of the temporal variations of the recycling rate (i.e., increasing in the intertropical convergence zone and decreasing in subtropical regions). All models, except one, successfully simulate not only the long-term trend but also the interannual variability of column water vapor. The simulations of precipitation are relatively poor, especially over the relatively short time scales, which lead to the discrepancy of the recycling rate between observations and the CMIP5 models. Comparisons of spatial patterns also suggest that the CMIP5 models simulate column water vapor better than precipitation. The comparative studies indicate the scope of improvement in the simulations of precipitation, especially for the relatively short-time-scale variations, to better simulate the recycling rate of atmospheric moisture, an important indicator of climate change. [ABSTRACT FROM AUTHOR]

In the tropics, the atmospheric circulation response to sea surface temperature (SST) anomalies is a crucial part of the tropical air-sea interaction-the primary process of tropical climate. How it will change under global warming is of great importance to tropical climate change. Here, it is shown that the atmospheric vertical circulation response to local SST anomalies will likely be weakened under global warming using 28 selected models from phase 5 of the Coupled Model Intercomparison Project. The weakening of the circulation response to SST anomalies is closely tied to the increased atmospheric stability under global warming, which increases at the same rate as the circulation response decreases-around 8% for 1 K of tropical-mean SST warming. The spatial pattern of background warming can modify-especially in the equatorial central-eastern Pacific-the spatial distribution of the changes in the circulation response. The atmospheric response to SST anomalies may increase where the local background warming is pronouncedly greater than the tropical mean. The general weakening of the atmospheric circulation response to SST anomalies leads to a decreased circulation response to the structured variability of tropical SST anomalies, such as the El Niño-Southern Oscillation and the Indian Ocean dipole. The decreased circulation response will offset some of the enhancement of the tropical rainfall response to these SST modes as a result of global-warming-induced moisture increase and also implies a decreased amplitude of the tropical air-sea interaction modes. [ABSTRACT FROM AUTHOR]

Portugal, which is located in the west limit of the Mediterranean subtropics, is a small region with a complex orography with large precipitation gradients and interannual variability. In this study, the newer and higher resolution regional climate simulations, covering Portugal, are evaluated in present climate and used to investigate the rainfall projections for the end of the twenty-first century, following the RCP4.5 and RCP8.5 emission scenarios. The EURO-CORDEX historical simulations, at 0.11° and at 0.44° resolution, are evaluated against gridded observations of precipitation, which allows the assembly of four multi-model ensembles. An extra simulation, at even higher resolution (9 km) with WRF is also analysed. In present climate, the models are able to describe the precipitation temporal and spatial patterns as well its distributions, although there is a large spread and an overestimation of larger rainfall quantiles. The multi-model ensembles show that selecting the best performing models adds quality to the overall representation of rainfall. The high-resolution simulations augment the spatial details of precipitation, but objectively do not seem to add value with respect to the coarse resolution. Regarding the RCP8.5 scenario, WRF and the multi-model ensembles consistently predict important losses of precipitation in Portugal in spring, summer and autumn, ranging from −10% and −50%. For all seasons, the changes are more severe in the southern basins. The precipitation distributions show, for all models, important reductions of the contribution from low to moderate/high precipitation bins and augments of days with strong rainfall. Furthermore, a prominent growth of high-ranking percentiles is predicted reaching values over 70% in some regions. Generally, the changes associated with the RCP4.5 scenario have the same signal and features, but with smaller magnitudes. [ABSTRACT FROM AUTHOR]

ABSTRACT The nature and timing of fluvial response and coincident changes in climate as inferred from multiple, independent proxies are examined in the wet tropics of north-eastern Australia. Chronostratigraphic data provide evidence for regionally synchronous fluvial aggradation at 30-13 ka, 8-5 ka and again from 1 ka. Terrace incision and removal occurred at 13-8 ka and 5-1 ka. A new synthesis of regional palaeoenvironmental proxy records spanning the last 30 ka highlights key periods of environmental change. Comparison of the records of fluvial and environmental change reveals the relationship is complex with no clear relationship between river aggradation/incision and wetter/drier conditions. The nature and timing of fluvial response in the wet tropics also shows broad similarities with coastal valleys in south-eastern New South Wales, suggesting continental-scale controls on fluvial response to changing climate during the Late Quaternary in Australia. Copyright © 2017 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The North Pacific Subtropical Gyre (NPSG) is one of the largest biomes on Earth. It has a semi-enclosed surface area of about 2 × 10 km and mean depth of nearly 5 km and includes a broad range of habitats from warm, light-saturated, nutrient-starved surface waters to the cold, nutrient-rich abyss. Microorganisms are found throughout the water column and are vertically stratified by their genetically determined metabolic capabilities that establish physiological tolerances to temperature, light, pressure, as well as organic and inorganic growth substrates. Despite the global significance of the NPSG for energy and matter transformations and its role in the oceanic carbon cycle, it is grossly undersampled and not well characterized with respect to ecosystem structure and dynamics. Since October 1988, interdisciplinary teams of scientists from the University of Hawaii and around the world have been investigating the NPSG ecosystem at Station ALOHA (A Long-term Oligotrophic Habitat Assessment), a site chosen to be representative of this expansive oligotrophic habitat, with a focus on microbial processes and biogeochemistry. At the start of this comprehensive field study, the NPSG was thought to be a 'Climax' community with a relatively stable plankton community structure and relatively low variability in key microbiological rates and processes. Now, after nearly three decades of observations and experimentation we present a new view of this old ocean, one that highlights temporal variability in ecosystem processes across a broad range of scales from diel to decadal and beyond. Our revised paradigm is built on the strength of high-quality time-series observations, on insights from the application of state-of-the-art -omics techniques (genomics, transcriptomics, proteomics and metabolomics) and, more recently, the discoveries of novel microorganisms and metabolic processes. Collectively, these efforts have led to a new understanding of trophic dynamics and population interactions in the NPSG. A comprehensive understanding of the environmental controls on microbial rates and processes, from genomes to biomes, will be required to inform the scientific community and the public at large about the potential impacts of human-induced climate change. The pace of new discovery, and the importance of integrating this new knowledge into conceptual paradigms and predictive models, is an enormous contemporary challenge with great scientific and societal relevance. [ABSTRACT FROM AUTHOR]

The impact of Pleistocene climate changes substantially varied between tropical regions, resulting in striking differences in angiosperm species richness caused by post-glacial recolonization delays. Tropical bryophytes, which have been perceived as extremely good dispersers due to biased rates of monoecy and hence spore production, differ strikingly from angiosperms in their similar patterns of species richness among tropical regions. Here, we analyse the patterns of beta diversity of tropical bryophytes to determine whether their high dispersal capacities have balanced patterns of species richness and erased any difference of post-glacial recolonization patterns between tropical regions. The partitioning of beta diversity for 7485 tropical moss species among 164 operational geographical units (OGUs) and 3276 liverwort and hornwort species in 154 OGUs revealed a slight, but significantly higher beta diversity among than within tropical regions. The nestedness component of beta diversity did not significantly differ between tropical regions. This indicates that, although regional migration rates were sufficient to erase differences of the impact of Pleistocene climate changes between tropical regions, the similar bryophyte species richness of tropical regions cannot be interpreted in terms of unrestricted migrations and that oceans act as a barrier to routine dispersal, which is sufficient to shape largescale floristic patterns. [ABSTRACT FROM AUTHOR]

In the past three decades, our global climate has been experiencing unprecedented warming. This warming has and will continue to significantly influence the structure and function of forest ecosystems. While studies have been conducted to explore the possible responses of forest landscapes to future climate change, the representative concentration pathways ( RCPs) scenarios under the framework of the Coupled Model Intercomparison Project Phase 5 ( CMIP5) have not been widely used in quantitative modeling research of forest landscapes. We used LANDIS- II, a forest dynamic landscape model, coupled with a forest ecosystem process model (Pn ET- II), to simulate spatial interactions and ecological succession processes under RCP scenarios, RCP2.6, RCP4.5 and RCP8.5, respectively. We also modeled a control scenario of extrapolating current climate conditions to examine changes in distribution and aboveground biomass ( AGB) among five different forest types for the period of 2010-2100 in Taihe County in southern China, where subtropical coniferous plantations dominate. The results of the simulation show that climate change will significantly influence forest distribution and AGB. (i) Evergreen broad-leaved forests will expand into Chinese fir and Chinese weeping cypress forests. The area percentages of evergreen broad-leaved forests under RCP2.6, RCP4.5, RCP8.5 and the control scenarios account for 18.25%, 18.71%, 18.85% and 17.46% of total forest area, respectively. (ii) The total AGB under RCP4.5 will reach its highest level by the year 2100. Compared with the control scenarios, the total AGB under RCP2.6, RCP4.5 and RCP8.5 increases by 24.1%, 64.2% and 29.8%, respectively. (iii) The forest total AGB increases rapidly at first and then decreases slowly on the temporal dimension. (iv) Even though the fluctuation patterns of total AGB will remain consistent under various future climatic scenarios, there will be certain responsive differences among various forest types. [ABSTRACT FROM AUTHOR]

Previous research has shown that subtropical and extratropical circulations are linked seasonally and in response to climate change. In particular, amplification (weakening) of subtropical stationary eddies is linked to a poleward (equatorward) shift of the extratropical circulation in the Northern Hemisphere. Here the mechanisms linking subtropical and extratropical circulation responses to climate change are examined using prescribed sea surface temperature aquaplanet simulations with a subtropical zonal asymmetry that mimics land-ocean contrasts. A poleward circulation shift occurs in response to uniform global warming even in the presence of subtropical stationary eddies. Subtropical stationary eddies exhibit a weak response to global warming; however, regional warming of temperature (or equivalent potential temperature) over land (ocean) increases (decreases) stationary eddy amplitude and shifts the extratropical circulation poleward (equatorward), consistent with comprehensive models. The stationary eddy response to regional warming is connected to regional moist entropy gradient, energy input to the atmosphere, and gross moist stability changes. Stationary eddy amplitude changes directly affect momentum and moist static energy transport following linear wave and mixing length theories. The transport changes do not follow a fixed-diffusivity framework. Extratropical transient eddy transport changes compensate ~70%-90% of the subtropical stationary eddy transport response. This assumes exact subtropical compensation accounts for a large fraction of the meridional shift of the extratropical circulation in response to regional climate change. [ABSTRACT FROM AUTHOR]

Many tropical islands have limited water resources with historically increasing demand, all potentially affected by a changing climate. The effects of climate change on island hydrology are difficult to model due to steep local precipitation gradients and sparse data. This work uses 10 statistically downscaled general circulation models (GCMs) under two greenhouse gas emission scenarios to evaluate the uncertainty propagated from GCMs in projecting the effects of climate change on water resources in a tropical island system. The assessment is conducted using a previously configured hydrologic model, the Precipitation Runoff Modelling System (PRMS) for Puerto Rico. Projected climate data and their modelled hydrologic variables versus historical measurements and their modelled hydrologic variables are found to have empirical distribution functions that are statistically different with less than 1 year of daily data aggregation. Thus, only annual averages of the projected hydrologic variables are employed as completely bias-corrected model outputs. The magnitude of the projected total low decreases in the four regions covering Puerto Rico, but with a large range of uncertainty depending on the makeup of the GCM ensemble. The multi-model mean projected total low decreases by 49-88%of historical amounts from the 1960s to the 2090s for the high emissions scenarios and by 39-79% for the low emissions scenarios. Subsurface low contributions decreased the least and groundwater low contributions decreased the most across the island. At locations critical to water supply for human use, projected stream low is shown to decrease substantially below projected withdrawals by 2099. [ABSTRACT FROM AUTHOR]

Climate change will alter the threats presented by invasive species. Increasing temperatures and changing precipitation regimes will likely simultaneously improve the suitability of a region for some species while decreasing it for others. We demonstrate the zero-sum game nature of these changes by modelling the changes to the projected distribution of 13 tropical and subtropical Tephritidae species in cities in Australia and New Zealand using published CLIMEX models. Under current climate conditions, tropical and warm temperate cities were suitable for more species than arid or cool temperate ones. All New Zealand cities increased in suitability, while Australian cities show more variable responses. The changes that occur under climate change are in line with the expectation of species ranges moving into higher latitudes but are also influenced by changes to the precipitation regime. With climate change, the nature of biosecurity threats will alter, the range of species able to survive in cool temperate regions is likely to increase with decreases in species ability to survive in tropical regions. Biosecurity agencies will need to respond to changing geography of threats. [ABSTRACT FROM AUTHOR]

The threat of anthropogenic climate change has seen a renewed focus on understanding contemporary patterns of species distribution. This is especially the case for the biota of tropical mountains, because tropical species often have particularly narrow elevational ranges and there are high levels of short-range endemism. Here we describe geographic patterns of ant diversity and distribution in the World Heritage-listed rainforests of the Australian Wet Tropics (AWT), revealing seasonal moisture stability to be an important environmental correlate of elevational patterns of species composition. We sampled ants in leaf litter, on the litter surface and on tree trunks at 26 sites from six subregions spanning five degrees of latitude and elevation ranges from 100–1,300 m. A total of 296 species from 63 genera were recorded. Species richness showed a slight peak at mid elevations, and did not vary significantly with latitude. Species composition varied substantially between subregions, and many species have highly localised distributions. There was very marked species turnover with elevation, with a particularly striking compositional disjunction between 600 m and 800 m at each subregion. This disjunction coincides with a strong environmental threshold of seasonal stability in moisture associated with cloud ‘stripping’. Our study therefore provides further support for climatic stability as a potential mechanism underlying patterns of diversity. The average height of orographic cloud layers is predicted to rise under global warming, and associated shifts in seasonal moisture stability may exacerbate biotic change caused by rising temperature alone. [ABSTRACT FROM AUTHOR]

The study focuses on the analysis of extreme precipitation events of the present and future climate over southern Africa. Parametric and non-parametric approaches are used to identify and analyse these extreme events in data from the Coordinated Regional Climate Downscaling Experiment (CORDEX) models. The performance of the global climate model (GCM) forced regional climate model (RCM) simulations shows that the models are able to capture the observed climatological spatial patterns of the extreme precipitation. It is also shown that the downscaling of the present climate are able to add value to the performance of GCMs over some areas depending on the metric used. The added value over GCMs justifies the additional computational effort of RCM simulation for the generation of relevant climate information for regional application. In the climate projections for the end of twenty-first Century (2069-2098) relative to the reference period (1976-2005), annual total precipitation is projected to decrease while the maximum number of consecutive dry days increases. Maximum 5-day precipitation amounts and 95th percentile of precipitation are also projected to increase significantly in the tropical and sub-tropical regions of southern Africa and decrease in the extra-tropical region. There are indications that rainfall intensity is likely to increase. This does not equate to an increase in total rainfall, but suggests that when it does rain, the intensity is likely to be greater. These changes are magnified under the RCP8.5 when compared with the RCP4.5 and are consistent with previous studies based on GCMs over the region. [ABSTRACT FROM AUTHOR]

The humid tropics represent only one example of the many places worldwide where anthropogenic disturbance and climate change are quickly affecting the feedbacks between water and trees. In this article, we address the need for a more long-term perspective on the effects of climate change on tropical montane cloud forests (TMCF) in order to fully assess the combined vulnerability and long- term response of tropical trees to changes in precipitation regimes, including cloud immersion. We first review the ecophysiological benefits that cloud water interception offers to trees in TMCF and then examine current climatological evidence that suggests changes in cloud base height and impending changes in cloud immersion for TMCF. Finally, we propose an experimental approach to examine the long-term dynamics of tropical trees in TMCF in response to environmental conditions on decade-to-century time scales. This information is important to assess the vulnerability and long-term response of TMCF to changes in cloud cover and fog frequency and duration. [ABSTRACT FROM AUTHOR]

The detectability of climate change signals such as a precipitation change depends on temporal and spatial averaging scales. The present study aims to clarify the dependence of the detectability on the two averaging scales by analyzing the difference in daily precipitation between present (1979-2003) and future (2075-2099) climates. The dataset for the analysis is obtained from an atmospheric general circulation model. The robustness of the precipitation change signal is evaluated with the signal-to-noise ratio (SNR), which is often used in statistical tests to detect climate change signals. The SNR is increased and the detectability of the precipitation change signal is enhanced with increases in the two averaging scales. When either averaging scale is increased (decreased) with a constant SNR, the other averaging scale needs to be decreased (increased); this is the trade-off relation between the two averaging scales. The trade-off relation is obtained quantitatively and provides useful information for climate change impact assessments using various temporal and spatial scales or resolutions. The characteristics of the trade-off relation are found to differ qualitatively among the tropics, mid-latitudes, and subpolar regions and to derive from the precipitation power spectrum representing spatio-temporal scales of precipitation-related meteorological phenomena, e.g., baroclinic waves. [ABSTRACT FROM AUTHOR]

The subsurface ocean response to anthropogenic climate forcing remains poorly characterized. From the Coupled Model Intercomparison Project (CMIP), a robust response of the lower thermocline is identified, where the warming is considerably weaker in the subtropics than in the tropics and high latitudes. The lower thermocline change is inversely proportional to the thermocline depth in the present climatology. Ocean general circulation model (OGCM) experiments show that sea surface warming is the dominant forcing for the subtropical gyre change in contrast to natural variability for which wind dominates, and the ocean response is insensitive to the spatial pattern of surface warming. An analysis based on a ventilated thermocline model shows that the pattern of the lower thermocline change can be interpreted in terms of the dynamic response to the strengthened stratification and downward heat mixing. Consequently, the subtropical gyres become intensified at the surface but weakened in the lower thermcline, consistent with results from CMIP experiments. [ABSTRACT FROM AUTHOR]

Differences between anomalously wet and dry rainy seasons over the period 1961-2001 in Equatorial East Africa (Kenya, northern Tanzania) are studied at local scale using a 53 rain-gauge network and analysing six intra-seasonal characteristics (ISCs): the onset and end dates, the wet spells number and length, daily mean rainfall amount and the dry spells length. As compared to anomalously dry Long Rains, anomalously wet ones record earlier onsets, more wet spells with higher daily mean rainfall amounts (above 14 mm/day). For the Short Rains, the end date is also widely modulated across the rain gauge network, and daily mean rainfall amounts above (below) 10 mm/day are more (less) frequent during anomalously wet (dry) seasons. The differences in the number, length and daily mean rainfall amount of wet spells between anomalously wet and anomalously dry rainy seasons is also analysed in an ensemble of 24 sea surface temperature-forced runs of the ECHAM4.5 Atmospheric General Circulation Model. For the Long Rains, results are inconsistent between runs which suggests a lack of reproducibility of the ISCs in the model. For the Short Rains, the ISCs distributions between anomalously wet and anomalously dry years are significantly different in most of the runs/locations. In particular, daily mean rainfall amounts above 8 mm/day are more (less) frequent in the model during anomalously wet (dry) years. [ABSTRACT FROM AUTHOR]

The main source of sea surface temperature (SST) variability in the Tropical Atlantic at interannual time scales is the Equatorial Mode or Atlantic El Niño. It has been shown to affect the adjacent continents and also remote regions, leading to a weakened Indian Monsoon and promoting La Niña-type anomalies over the Pacific. However, its effects in a warmer climate are unknown. This work analyses the impact of the Equatorial Mode at the end of the twenty first century by means of sensitivity experiments with an atmosphere general circulation model. The prescribed boundary conditions for the future climate are based on the outputs from models participating in the coupled model intercomparison project-phase V. Our results suggest that even if the characteristics of the Equatorial Mode at the end of the twenty first century remained equal to those of the twentieth century, there will be an eastward shift of the main rainfall positive anomalies in the Tropical Atlantic and a weakening of the negative rainfall anomalies over the Asian monsoon due to the change in climatological SSTs. We also show that extratropical surface temperature anomalies over land related to the mode will change in regions like Southwestern Europe, East Australia, Asia or North America due to the eastward shift of the sea level pressure systems and related surface winds. [ABSTRACT FROM AUTHOR]

Climate models with variable-resolution grids offer a computationally less expensive way to provide more detailed information and increased accuracy by resolving processes that cannot be adequately represented by a coarser grid. This study uses the Model for Prediction Across Scales-Atmosphere (MPAS-A), consisting of a nonhydrostatic dynamical core and a subset of Weather Research and Forecasting (WRF) model physics, to investigate the potential benefits of using tropical channel refinement. The simulations are performed with an idealized aquaplanet configuration using 30 and 240 km global grid spacing, and two variable-resolution grids spanning the same grid spacing range; one with a narrow (20°S-20°N) and one with a wide (30°S-30°N) tropical channel refinement. Increasing resolution in the tropics impacts both the tropical and extratropical circulation. Compared to the 30 km global grid, both refined channel simulations exhibit slightly stronger updrafts inside the Hadley cell resulting in more resolved precipitation. Using a wider tropical refinement leads to a closer correspondence with the global high-resolution grid. While different grid spacings produce similar cloud size distributions that are consistent with observations, the dependence of precipitation rate on cloud size varies among simulations. The refined channel simulations show improved tropical and extratropical precipitation relative to the global coarse simulation. All simulations show a single precipitation peak centered on the equator. Although the results show that tropical refinement is an effective method for avoiding artifacts due to grid resolution sensitivities seen in earlier studies that only refined a portion of the tropics, some biases remain well inside of the refinement region. [ABSTRACT FROM AUTHOR]

Relationships between shifts in climatic and other environmental conditions and changes in the character and dynamics of phytoplankton blooms were examined in three interconnected subtropical lagoons on the east coast of Florida, i.e., Mosquito Lagoon, Indian River Lagoon, and Banana River Lagoon, from 1997 to 2013. Phytoplankton blooms were a common feature through most of the study period in two of the lagoons. From 1997 to 2009, blooms in the latter two lagoons were typically dominated by dinoflagellates in the warm wet season and diatoms in the cool dry season. Blooms of the dominant bloom-forming dinoflagellate species Pyrodinium bahamense were positively correlated to rainfall levels, indicating a link to enhanced external nutrient loads. In 2011-2013, major blooms were observed in all three lagoons, but unlike the previous 14 years, they were dominated by picoplanktonic eukaryotes, including a chlorophyte, Pedinophyceae sp., and the brown tide species Aureoumbra lagunensis. The results suggest that extreme climatic conditions, including record cold winter water temperatures and low rainfall levels, were major driving factors in this state shift in the character of blooms, through a wide range of effects including die-offs of benthic flora and fauna, suppression of grazer populations, alteration of nutrient regimes, and uncharacteristic water column conditions, such as elevated salinities and light attenuation. [ABSTRACT FROM AUTHOR]

Assessing temporal variability in extreme rainfall events before the historical era is complicated by the sparsity of long-term "direct" storm proxies. Here we present a 2,200-y-long, accurate, and precisely dated record of cave flooding events from the northwest Australian tropics that we interpret, based on an integrated analysis of meteorological data and sediment layers within stalagmites, as representing a proxy for extreme rainfall events derived primarily from tropical cyclones (TCs) and secondarily from the regional summer monsoon. This time series reveals substantial multicentennial variability in extreme rainfall, with elevated occurrence rates characterizing the twentieth century, 850-1450 CE (Common Era), and 50-400 CE; reduced activity marks 1450-1650 CE and 500-850 CE. These trends are similar to reconstructed numbers of TCs in the North Atlantic and Caribbean basins, and they form temporal and spatial patterns best explained by secular changes in the dominant mode of the El Niño/Southern Oscillation (ENSO), the primary driver of modern TC variability. We thus attribute long-term shifts in cyclogenesis in both the central Australian and North Atlantic sectors over the past two millennia to entrenched El Niño or La Niña states of the tropical Pacific. The influence of ENSO on monsoon precipitation in this region of northwest Australia is muted, but ENSO-driven changes to the monsoon may have complemented changes to TC activity. [ABSTRACT FROM AUTHOR]

Large-scale studies are needed to increase our understanding of how large-scale conservation threats, such as climate change and deforestation, are impacting diverse tropical ecosystems. These types of studies rely fundamentally on access to extensive and representative datasets (i.e., “big data”). In this study, I asses the availability of plant species occurrence records through the Global Biodiversity Information Facility (GBIF) and the distribution of networked vegetation census plots in tropical South America. I analyze how the amount of available data has changed through time and the consequent changes in taxonomic, spatial, habitat, and climatic representativeness. I show that there are large and growing amounts of data available for tropical South America. Specifically, there are almost 2,000,000 unique geo-referenced collection records representing more than 50,000 species of plants in tropical South America and over 1,500 census plots. However, there is still a gaping “data void” such that many species and many habitats remain so poorly represented in either of the databases as to be functionally invisible for most studies. It is important that we support efforts to increase the availability of data, and the representativeness of these data, so that we can better predict and mitigate the impacts of anthropogenic disturbances. [ABSTRACT FROM AUTHOR]

In this study, reasons for spatial variability in prediction skill of seasonal mean sea surface temperature (SST) are investigated. The analysis explores the connection between the spatial variation of SST prediction skill in tropical latitudes and local simultaneous correlation between observed SST and precipitation (SST-P). The results show that high (low) SST prediction skills and slow (fast) decay in skill with lead time are generally collocated with large positive (weakly positive or negative) SST-P correlations. The reasons for spatial variation in SST-P correlation can be explained by whether the primary forcing is from the ocean to the atmosphere or vice versa. Over regions where the ocean is generally known to force the atmosphere, it is found that SST-P correlation has large positive values. Over regions where the atmosphere forces ocean, SST-P correlation is weak due to intrinsically unpredictable nature of atmospheric variability. The physical explanation for spatial variation in SST-P correlation, and apparent link between the spatial variations in SST-P correlation and spatial variations in skill of SST predictions also establishes a physical basis for the latter. As a corollary, low SST prediction skill in coupled forecast models over certain geographical regions may be due to the inherent limits on predictability in addition to the contribution from model biases or initialization errors. [ABSTRACT FROM AUTHOR]

Factors that drive species richness over space and time are still poorly understood and are often context specific. Identifying these drivers for ant diversity has become particularly relevant within the context of contemporary global change events. We report on a long-term bi-annual (wet and dry seasons), standardized sampling of epigeal ants over a five year period on the mesic and arid aspects of an inselberg (Soutpansberg Mountain Range) in the tropics of Africa. We detail seasonal, annual and long-term trends of species density, test the relative contribution of geometric constraints, energy, available area, climate, local environmental variables, time, and space in explaining ant species density patterns through Generalized Linear Mixed Models (GLMM) where replicates were included as random factors to account for temporal pseudo-replication. Seasonal patterns were very variable and we found evidence of decreased seasonal variation in species density with increased elevation. The extent and significance of a decrease in species density with increased elevation varied with season. Annual patterns point to an increase in ant diversity over time. Ant density patterns were positively correlated with mean monthly temperature but geometric constraints dominated model performance while soil characteristics were minor correlates. These drivers and correlates accounted for all the spatio-temporal variability in the database. Ant diversity was therefore mainly determined by geometric constraints and temperature while soil characteristics (clay and carbon content) accounted for smaller but significant amounts of variation. This study documents the role of season, elevation and their interaction in affecting ant species densities while highlighting the importance of neutral processes and temperature in driving these patterns. [ABSTRACT FROM AUTHOR]

Future changes of terrestrial ecosystems due to changes in atmospheric CO concentration and climate are subject to a large degree of uncertainty, especially for vegetation in the Tropics. Here, we evaluate the natural vegetation response to projected future changes using an improved version of a dynamic vegetation model (CLM-CN-DV) driven with climate change projections from 19 global climate models participating in the Coupled Model Intercomparison Project Phase 5 (CMIP5). The simulated equilibrium vegetation distribution under historical climate (1981-2000) has been compared with that under the projected future climate (2081-2100) scenario for Representative Concentration Pathway 8.5 (RCP8.5) to qualitatively assess how natural potential vegetation might change in the future. With one outlier excluded, the ensemble average of vegetation changes corresponding to climates of 18 GCMs shows a poleward shift of forests in northern Eurasia and North America, which is consistent with findings from previous studies. It also shows a general 'upgrade' of vegetation type in the Tropics and most of the temperate zones, in the form of deciduous trees and shrubs taking over C3 grass in Europe and broadleaf deciduous trees taking over C4 grasses in Central Africa and the Amazon. LAI and NPP are projected to increase in the high latitudes, southeastern Asia, southeastern North America, and Central Africa. This results from CO fertilization, enhanced water use efficiency, and in the extra-tropics warming. However, both LAI and NPP are projected to decrease in the Amazon due to drought. The competing impacts of climate change and CO fertilization lead to large uncertainties in the projection of future vegetation changes in the Tropics. [ABSTRACT FROM AUTHOR]