Multidecadal Oscillation Research Articles

Nonlinear Trend and Multiscale Variability of Dry Spells in Senegal (1951–2010)

Dry spells occurring during the rainy season have significant implications for agricultural productivity and socioeconomic development, particularly in rainfed agricultural countries such as Senegal. This study employs various chaos-theory-based tools, including the lacunarity method, rescaled analysis, and the improved complete ensemble empirical mode decomposition with adaptive noise (ICEEMDAN) method, to investigate the distribution, predictability, and multiscale properties of the annual series of maximum dry spell length (AMDSL) in Senegal during the rainy season. The analysis focuses on 29 stations across Senegal, spanning the period from 1951 to 2010. The findings reveal persistent behavior in the AMDSL across nearly all stations, indicating that predictive models based on extrapolating past time trends could enhance AMDSL forecasting. Furthermore, a well-defined spatial distribution of the lacunarity exponent β is observed, which exhibits a discernible relationship with rainfall patterns in Senegal. Notably, the lacunarity exponent displays a south-to-north gradient for all thresholds, suggesting its potential for distinguishing between different drought regimes and zones while aiding in the understanding of spatiotemporal rainfall variability patterns. Moreover, the analysis identifies five significant intrinsic mode functions (IMFs) characterized by different periods, including interannual, interdecadal, and multidecadal oscillations. These IMFs, along with a nonlinear trend, are identified as the driving forces behind AMDSL variations in Senegal. Among the inter-annual oscillations, a 3-year quasi-period emerges as the primary contributor and main component influencing AMDSL variability. Additionally, four distinct morphological types of nonlinear trends in AMDSL variations are identified, with increasing–decreasing and increasing trends being the most prevalent. These findings contribute to a better understanding of the variability in annual maximum dry spell lengths, particularly in the context of climate change, and provide valuable insights for improving AMDSL forecasting. Overall, this study enhances our comprehension of the complex dynamics underlying dry spell occurrences during the rainy season and presents potential avenues for predicting and managing the AMDSL in Senegal.

Investigation of marine temperature changes across temporal and spatial Gradients: Providing a fundament for studies on the effects of warming on marine ecosystem function and biodiversity

A current critical issue in climate change studies is how temperature changes and shifts on different spatial and temporal scales can affect organisms in terms of trends, variability and frequency of extremes. In this paper, we analysed marine temperature data on different temporal and spatial scales. We related the sea surface temperature data from the Helgoland Roads Time Series, one of the most important and detailed long-term in situ marine ecological time series, to the Sylt Roads, North Sea, Germany, Europe, North Atlantic and Northern Hemisphere surface temperatures. All time series showed a distinct upwards shift in temperature in the late 1980s, early 1990s, with positive trends in overall for the period between 1962 and 2019 ranging from 1 to 2 °C over 57 years. We quantified changes in temperature variability by comparing the years before and after 1990, on both long-term and seasonal scales. At Helgoland and Sylt, an increase in the number of warmer days in summer and a decrease in extremely cold days in winter are the new characteristics of the temperature pattern after 1990; higher than expected temperatures now also occur earlier during the year. For these locations, we observed the highest trends overall, i.e. of around 0.3 °C/decade. The observed bimodal shape of the probability density functions, characterized by winter and summer modes, had become more heterogeneous, with the cold mode peak moving to higher values and the steepness to the peak increasing, which is a consequence of a decrease in extremely cold days. North Atlantic Oscillation (NAO) and Multidecadal Oscillation (AMO) large-scale phenomena had no significant correlations or, for the NAO, were limited to the winter season at the regional and local scales. The closest landmass (mainland Germany) temperature was highly correlated with the North Sea sites. Taken together, our results suggest that marine pelagic ecosystems and their species are subject to temperature shifts with similar patterns but with variations in magnitude at the different scales. Temperature is one of the main drivers of species diversity and distribution, and this manifests on different spatial and temporal scales depending on population growth, life stages, cycles and habitat. Accordingly, we here present the temperature changes on the appropriate spatio-temporal scales, and thus provide the suitable and useful fundament for studies on the effects of warming on marine ecosystem function and biodiversity.

A multidecadal oscillation in precipitation and temperature series is pronounced in low flow series from Puget Sound streams

AbstractIn Pacific Northwest streams, summer low flows limit water available to competing instream (salmon) and out‐of‐stream (human) uses, creating broad interest in how and why low flows are trending. Analyses that assumed linear (monotonic) change over the last ~60 years revealed declining low flow trends in minimally disturbed streams. Here, polynomials were used to model flow trends between 1929 and 2015. A multidecadal oscillation was observed in flows, which increased initially from the 1930s until the 1950s, declined until the 1990s, and then increased again. A similar oscillation was detected in precipitation series, and opposing oscillations in surface temperature, Pacific Decadal Oscillation, and Interdecadal Pacific Oscillation series. Multidecadal oscillations with similar periods to those described here are well known in climate indices. Fitted model terms were consistent with flow trends being influenced by at least two drivers, one oscillating and the other monotonic. Anthropogenic warming is a candidate driver for the monotonic decline, and variation in (internal) climatic circulation for the oscillating trend, but others were not ruled out. The recent upturn in streamflows suggests that anthropogenic warming has not been the dominant factor driving streamflow trends, at least until 2015. Climate projections based on simulations that omit drivers of multidecadal variation are likely to underestimate the range, and rate of change, of future climatic variation.

Interdecadal Oscillation of the Ocean Heat Content as a Contribution to Understanding of Physical Aspects of the Present-Day Climate

A Specific feature of the present-day climate dynamics consists in its multidecadal oscillations with a period of about 20–60 years, and intradecadal disturbances with time scales of 2–8 years. The period of 1940–1999 was distinctive due to the two–phase structure in which the initial phase (1940–1974) was substantially dry, and the final one (1975–1999) was relatively humid. The transition of the climate from the dry to the humid phase in the mid-1970s was recognized as a climatic shift. The certain globality and quasisynchronism of multidecadal climate changes occur involving planetary thermodynamic structures in the two most important components of the climate system, namely, the ocean and the atmosphere. The search for the origin of the observed present-day climate variability revealed the World Ocean (WO) active upper layer (AUL) heat content to demonstrate sequential multidecadal phases of heat accumulation and discharge consistent with multidecadal phases of climate disturbances. Thus, the WO AUL heat accumulation phase corresponds to a dry climate, and its thermal discharge corresponds to a relatively humid one. The mechanism of the observed multidecadal phase variability in the present-day climate consists of the planetary intrasystemic redistribution of heat between WO and continental air masses, where the general circulation of the atmosphere plays the role of an intermediary.

Coupled stratosphere-troposphere-Atlantic multidecadal oscillation and its importance for near-future climate projection

Northern Hemisphere (NH) climate has experienced various coherent wintertime multidecadal climate trends in stratosphere, troposphere, ocean, and cryosphere. However, the overall mechanistic framework linking these trends is not well established. Here we show, using long-term transient forced coupled climate simulation, that large parts of the coherent NH-multidecadal changes can be understood within a damped coupled stratosphere/troposphere/ocean-oscillation framework. Wave-induced downward propagating positive stratosphere/troposphere-coupled Northern Annular Mode (NAM) and associated stratospheric cooling initiate delayed thermohaline strengthening of Atlantic overturning circulation and extratropical Atlantic-gyres. These increase the poleward oceanic heat transport leading to Arctic sea-ice melting, Arctic warming amplification, and large-scale Atlantic warming, which in turn initiates wave-induced downward propagating negative NAM and stratospheric warming and therefore reverse the oscillation phase. This coupled variability improves the performance of statistical models, which project further weakening of North Atlantic Oscillation, North Atlantic cooling and hiatus in wintertime North Atlantic-Arctic sea-ice and global surface temperature just like the 1950s–1970s.

The Last 1200 Years of Rainfall/Runoff Variability along the Central Mexico Pacific Coast Associated with the North American Monsoon

This study presents new evidence for long-term variability in the late Holocene North American Monsoon (NAM), Pacific coast of Mexico. We have carried out a rock magnetic study on two deep-sea sediment cores from the Pacific coast Pescadero Basin. The magnetic intensities estimate total magnetic material and are a proxy for total clastic sediment. Ratios of magnetic intensities estimate the grain size of magnetic material. The rock magnetic data show a decimeter scale, multi-decadal oscillation with fourteen cycles (A-N) over the last 1200 years. These oscillations reflect alternating intervals of stronger/coarser magnetic/clastic flux to the coastal ocean and intervals of weaker/finer magnetic flux. We think these variations are caused by variations in long-term dominance of the NAM; summer (wet) monsoons produce rainy conditions (with runoff) while winter (dry) monsoons produce significant offshore winds, increased upwelling/biological productivity. We can correlate our variability to two other published studies southeast of Pescadero Basin, coastal lake sediments in Laguna de Juanacatlan and a Juxtlahuaca Cave stalagmite. Both of these studies estimate local rainfall. We see evidence of the same pattern of multi-decadal rainfall-runoff variability in these records as we see in Pescadero Basin, which is synchronous to within ±25 years over the last 1200 years. The multi-dacadal pattern of hydrologic variability in all three records varies in cycle duration from ~90-years wet/dry cycles in the Little Ice Age (1400–1850 AD) to ~60-years cycles in the Medieval Climate Optimum (1100–1400 AD). This variability in cycle duration suggests some chaotic nature to the regional NAM climate pattern or some long-term non-linear forcing (PDO?).

Subpolar Gyre – AMOC – Atmosphere Interactions on Multidecadal Timescales in a Version of the Kiel Climate Model

AbstractThere is a controversy about the nature of multidecadal climate variability in the North Atlantic (NA) region, concerning the roles of ocean circulation and atmosphere-ocean coupling. Here we describe NA multidecadal variability from a version of the Kiel Climate Model, in which both subpolar gyre (SPG)-Atlantic Meridional Overturning Circulation (AMOC) and atmosphere-ocean coupling are essential. The oceanic barotropic and meridional overturning streamfunctions, and sea level pressure are jointly analyzed to derive the leading mode of Atlantic sector variability. This mode accounting for 23.7 % of the total combined variance is oscillatory with an irregular periodicity of 25-50 years and an e-folding time of about a decade. SPG and AMOC mutually influence each other and together provide the delayed negative feedback necessary for maintaining the oscillation. An anomalously strong SPG, for example, drives higher surface salinity and density in the NA’s sinking region. In response, oceanic deep convection and AMOC intensify, which, with a time delay of about a decade, reduces SPG strength by enhancing upper-ocean heat content. The weaker gyre leads to lower surface salinity and density in the sinking region, which reduces deep convection and eventually AMOC strength. There is a positive ocean-atmosphere feedback between the sea surface temperature and low-level atmospheric circulation over the Southern Greenland area, with related wind stress changes reinforcing SPG changes, thereby maintaining the (damped) multidecadal oscillation against dissipation. Stochastic surface heat-flux forcing associated with the North Atlantic Oscillation drives the eigenmode.

Climate signals in river flood damages emerge under sound regional disaggregation

Climate change affects precipitation patterns. Here, we investigate whether its signals are already detectable in reported river flood damages. We develop an empirical model to reconstruct observed damages and quantify the contributions of climate and socio-economic drivers to observed trends. We show that, on the level of nine world regions, trends in damages are dominated by increasing exposure and modulated by changes in vulnerability, while climate-induced trends are comparably small and mostly statistically insignificant, with the exception of South & Sub-Saharan Africa and Eastern Asia. However, when disaggregating the world regions into subregions based on river-basins with homogenous historical discharge trends, climate contributions to damages become statistically significant globally, in Asia and Latin America. In most regions, we find monotonous climate-induced damage trends but more years of observations would be needed to distinguish between the impacts of anthropogenic climate forcing and multidecadal oscillations.

Multidecadal and 6-year variations of LOD

The subject of our study is 6-, 20- and 60-year oscillations in the length of day (LOD). Spectral and wavelet analyses of LOD time series have been performed, multidecadal harmonics have been adjusted and simple prediction has been made. Input from the variations of the angular momentum of the ocean and the atmosphere into LOD changes at 6-, 20- and 60-year periods has been analysed. We found out that the oceanic forcing (OAM) of LOD at 20- and 60-year scales is less than 20 microseconds, and 6-year oscillation after atmospheric effects subtraction becomes quite stable with the amplitude of around 0.2 milliseconds. To perform filtering, we used Panteleev’s band-pass filter. Since multidecadal oscillations with the amplitude up to 3 milliseconds remain unexplained, we compared them with temperature and sea level anomalies, Chandler wobble and its excitation envelope, and with the Earth’s magnetic dipole strength anomaly, a number of processes contain multidecadal variations, the signature of which is quite similar to LOD changes.

Trend of extreme rainfall events using suitable Global Circulation Model to combat the water logging condition in Kolkata Metropolitan Area

Kolkata Metropolitan Area (KMA) is one of the most densely populated areas in the world, where extreme precipitation events result in frequent waterlogging and flood inundation conditions which can adversely affect the city. In this study, we evaluate the nature and trend of annual-maximum precipitation events by employing suitable Global Circulation Models (GCMs). The trend of observed annual maximum daily rainfall from 1901 to 2013 has been analysed through linear regression, recurrence period and multi-decadal oscillation. The results show that the observed rainfall of the given region follows the natural variability and oscillation trend. TRMM time-series data (2000–2019) is employed to validate the ground-station data series using Modified Mann Kendall and Sen’s Slope estimator test, which shows a correlation of 0.88. In addition, suitable bias-corrected GCMs have been selected to estimate the future precipitation in the given study area. Analysis of future rainfall for the period of 2071–2100 revealed that the RCPs are showing an increase in the extreme precipitation intensity by 1.5, 2.3 and 3 times considering RCP 4.5, 6.0 and 8.5 scenarios respectively. The presented results serve as the preliminary data for future planning and designing efficient flood management strategies in the given area to combat water-logging in KMA.

West Asian climate during the last millennium according to the EC-Earth model

West Asia is one of the most vulnerable regions to ongoing climate change but has been poorly investigated. Therefore, it is crucial to understand the impact of anthropogenic greenhouse gas, natural forcing, and internal climate variability on temperature and rainfall in this region. In this study, we focus on the climate of West Asia during the last millennium by using a transient simulation of the global earth system model EC-Earth (v3.1). The model performs well in terms of present-day temperature and precipitation patterns and their regional averages. Time series of yearly-mean precipitation and temperature of West Asia show that precipitation increases until the start of the Little Ice Age (1450–1850 CE) and subsequently decreases, whereas temperature shows a cooling trend during the entire last millennium. We first discuss the model output data for climate trends during two periods, 850–1450 CE and 1450–1850 CE. In 850–1450 CE, the largest wetting trend occurred in the eastern regions to the north of the Persian Gulf because of a westward shift of the Indian precipitation core and more moisture transport from the Arabian Sea. The precipitation trend in 1450–1850 CE had a different pattern with a drying trend in the west of the Caspian Sea and overall getting less wet compared with the first period. Temperature showed cooling trends for both periods with the largest values happening in the northern regions. The North Atlantic sea surface temperature cooling and the subsequent change in atmospheric circulation played a role in the wetting and cooling of West Asia. In the second part of the study, we remove the trends and discuss the multi-decadal variability of West Asian climate. It was found that Atlantic multi-decadal and Pacific decadal oscillations strongly contributed to West Asian temperature variability. For West Asian precipitation variability, we found remote connections with the Nordic seas and tropical Pacific Ocean.

Correlations between hydrological drought and climate indices with respect to the impact of a large reservoir

With the construction of numerous water conservation projects, an assessment of the correlation between the evolution of hydrological drought and climate indices under in the context of large reservoirs helps to elucidate the response of the global environment to variations in hydrological drought. This study is focused on the Jinjiang River basin in southeastern China, where the Shilong hydrological station is affected by a large reservoir, and the Anxi hydrological station is not. Based on monthly streamflow data from 1960 to 2010, the Standardized Streamflow Index (SSI) was used to identify hydrological droughts. Pearson correlation coefficients (PCC) and the cross-wavelet transform (XWT) method were used to reveal detailed correlations between the SSI and climate indices. The correlations detected for both stations were then compared. The results indicate the following: (1) the correlations between the SSI and both ENSO (EI Nino-Southern Oscillation) and PDO (Pacific Decadal Oscillation) are more obvious than those of the other two climate indices, NAO (North Atlantic Oscillation) and AMO (Multi-decadal Oscillation). Moreover, the effect of EI Nino was more notable than that of La Nino. (2) Apparent intra-annual (12–48 months) and inter-decadal (128–256 months) common oscillation cycles between the SSI and ENSO were detected. Furthermore, there is an unequal lag time (1.47–1.80 months) between the coherence cycles of the SSI with ENSO. (3) The regulation functions of the large reservoir with respect to streamflow changed the correlations between the SSI and climate indices. The correlations at Shilong were weaker (stronger) than those at Anxi in the dry (wet) season.

Changing Salinity Gradients in the Baltic Sea As a Consequence of Altered Freshwater Budgets

AbstractClimate change is expected to enhance the hydrological cycle in northern latitudes reducing the salinity in the Baltic Sea, a land‐locked marginal sea with a large catchment area located in northern Europe. With the help of ocean simulations forced by historical atmospheric and hydrological reconstructions and local observations, we analyzed long‐term changes in the sea surface salinity of the Baltic Sea as well as its latitudinal gradient. The variability of both is dominated by multidecadal oscillations with a period of about 30 years, while both atmospheric variables, wind and river runoff, contribute to this variability. Centennial changes show a statistically significant positive trend in the North‐South gradient of sea surface salinity for 1900–2008. This change is mainly attributed to increased river runoff from the northernmost catchment indicating a footprint of the anthropogenic impact on salinity with consequences for the marine ecosystem and species distributions.

Examining trends of hydro-meteorological extremes in the Shire River Basin in Malawi

Malawi experiences frequent floods and droughts and these hydrological extremes kill and displace people and damage infrastructure. In recent years, the trend of these extreme events has increased in frequency and magnitude and has threatened socio-economic development of the country. Analysis of trends and frequency of hydro-meteorological extremes that cause floods and droughts is very vital in understanding the hydrological systems and this may assist in averting disasters associated with those extremes. For extremes extracted from long-term hydro-meteorological records, a significant trend may indicate a shift from the natural changes to the changes induced by human activities on one hand and on the other hand, decadal or multi-decadal oscillations in the occurrence of hydro-meteorological extremes may demonstrate the influence of the (multi-) decadal persistence of the climate system. In Malawi, studies on trends of hydro-meteorological extremes of rainfall, temperature and streamflows are scanty as most studies have focused on the means. This study, therefore, aimed at examining trends and frequency of these hydro-meteorological extremes in the Shire River Basin in Malawi. Daily scale data from 1961 to between 2005 and 2015 were collected from 22 rainfall stations, 12 temperature stations and 10 river discharge station within the study area. The hydro-meteorological extremes were analyzed using annual maximas and annual minimas of the daily hydro-meteorological data. Significance and direction of trends in these extreme indices were examined using the non-parametric Mann–Kendall test statistic. The Peak-Over-Threshold (POT) approach, applying the Generalized Pareto Distribution (GPD) was used to analyze the distribution of the extremes. Study results have shown that temperature extremes have an increasing trend which is significant at 5% significance level. In terms of streamflows, both the peak and low flow extremes have shown a decreasing trend, which is consistent with the decreasing trends observed in rainfall extremes. Analysis of frequency of extreme events has shown that extremely high rainfall events have a high probability of occurrence while streamflow extremes will not occur frequently. These findings have provided key insights that are key in understanding the temporal occurrence of hydro-meteorological extremes in the basin, which are of benefit to the regional water resources planning and development.

High-resolution reconstruction of Indian summer monsoon during the Bølling-Allerød from a central Indian stalagmite

Although the Indian monsoon during the last deglaciation has been reconstructed from marine sediments from the Indian Ocean, a detailed high resolution (decadal or less) reconstruction from terrestrial records such as speleothems has been lacking from the core monsoon zone of India. Such reconstructions can help determine whether the monsoon is controlled by insolation alone or also other feedbacks within the Earth system. We present here a new data set of high resolution record based on 1186 measurements of δ18O from a 43-cm long speleothem from the Kailash Cave, Central India that record Indian Summer Monsoon (ISM) rainfall changes encompassing the Bølling-Allerød interstadial (14.8 to 12.6 ka). The growth rates varied from 0.6 to 37.1 mm/year, with the monsoon strength. This is also confirmed by the δ18O record, with a rapid increase in the rainfall during 14.8 to 14.5 ka, stabilizing subsequently, and exhibiting centennial and multi-decadal oscillations. Our results corroborate an earlier observation that although the boundary conditions during the last several millennia and the Bølling-Allerød were very different, multi-decadal and centennial climate dynamics may have been similar. In addition to solar insolation, our results show a relation of ISM shifts to coupled ocean-atmospheric processes. Strong link of Indian Summer Monsoon (ISM) variability to proxy records from the southern hemisphere is also noted in this work.

Water Vapor Transport Related to the Interdecadal Shift of Summer Precipitation over Northern East Asia in the Late 1990s

In this study, an interdecadal shift of summer precipitation over northern East Asia (NEA) was identified, demonstrating that summer precipitation decreased abruptly after 1998/99. The synchronous shift in summer moisture budget and water vapor transport over NEA was further investigated by using the NCEP/NCAR reanalysis data. The results indicate that water vapor transported northward into NEA from three low-latitude paths was limited because most water vapor was transported eastward. Water vapor transported from the westerly path in mid–high (WMH) latitudes exhibited significant correlations with summer precipitation in NEA and experienced a significant adjustment in the late 1990s. Regarding the spatial distributions of water vapor transport, less input was found through the western boundary while more output occurred through the eastern boundary of NEA, and zonal water vapor transport fluxes mainly concentrated at the low to middle levels, which led to the summer precipitation shift in NEA around the late 1990s. Furthermore, it is also confirmed that the wind anomalies (rather than the moisture disturbance) as the dominant internal dynamic factor and Pacific Decadal Oscillation/Atlantic Multidecadal Oscillation (PDO/AMO) as possible external force played important roles in influencing the water vapor transport and causing the summer precipitation shift over NEA in the late 1990s.

A Climate Index Optimized for Longshore Sediment Transport Reveals Interannual and Multidecadal Littoral Cell Rotations

AbstractA recent 35‐year endpoint shoreline change analysis revealed significant counterclockwise rotations occurring in north‐central Oregon, USA, littoral cells that extend 10s of kilometers in length. While the potential for severe El Niños to contribute to littoral cell rotations at seasonal to interannual scale was previously recognized, the dynamics resulting in persistent (multidecadal) rotation were unknown, largely due to a lack of historical wave conditions extending back multiple decades and the difficulty of separating the timescales of shoreline variability in a high energy region. This study addresses this question by (1) developing a statistical downscaling framework to characterize wave conditions relevant for longshore sediment transport during data‐poor decades and (2) applying a one‐line shoreline change model to quantitatively assess the potential for such large embayed beaches to rotate. A climate INdex was optimized to capture variability in longshore wave power as a proxy for potential LOngshore Sediment Transport (LOST_IN), and a procedure was developed to simulate many realizations of potential wave conditions from the index. Waves were transformed dynamically with Simulating Waves Nearshore to the nearshore as inputs to a one‐line model that revealed shoreline rotations of embayed beaches at multiple time and spatial scales not previously discernible from infrequent observations. Model results indicate that littoral cells respond to both interannual and multidecadal oscillations, producing comparable shoreline excursions to extreme El Niño winters. The technique quantitatively relates morphodynamic forcing to specific climate patterns and has the potential to better identify and quantify coastal variability on timescales relevant to a changing climate.

Interannual-to-multidecadal hydroclimate variability and its sectoral impacts in northeastern Argentina

Abstract. This study examines the joint variability of precipitation, river streamflow and temperature over northeastern Argentina; advances the understanding of their links with global SST forcing; and discusses their impacts on water resources, agriculture and human settlements. The leading patterns of variability, and their nonlinear trends and cycles are identified by means of a principal component analysis (PCA) complemented with a singular spectrum analysis (SSA). Interannual hydroclimatic variability centers on two broad frequency bands: one of 2.5–6.5 years corresponding to El Niño Southern Oscillation (ENSO) periodicities and the second of about 9 years. The higher frequencies of the precipitation variability (2.5–4 years) favored extreme events after 2000, even during moderate extreme phases of the ENSO. Minimum temperature is correlated with ENSO with a main frequency close to 3 years. Maximum temperature time series correlate well with SST variability over the South Atlantic, Indian and Pacific oceans with a 9-year frequency. Interdecadal variability is characterized by low-frequency trends and multidecadal oscillations that have induced a transition from dryer and cooler climate to wetter and warmer decades starting in the mid-twentieth century. The Paraná River streamflow is influenced by North and South Atlantic SSTs with bidecadal periodicities. The hydroclimate variability at all timescales had significant sectoral impacts. Frequent wet events between 1970 and 2005 favored floods that affected agricultural and livestock productivity and forced population displacements. On the other hand, agricultural droughts resulted in soil moisture deficits that affected crops at critical growth stages. Hydrological droughts affected surface water resources, causing water and food scarcity and stressing the capacity for hydropower generation. Lastly, increases in minimum temperature reduced wheat and barley yields.

Influence of Climatic Phenomena on Sedimentation and Increase of Lake Enriquillo in Dominican Republic, 1900-2014

From 2003 to 2013, Enriquillo Lake, Dominican Republic, showed an increase in water level of 13 meters, with its level changing from 42 to 29 meters below sea level (BSL). In 2003, its maximum depth was approximately 24 meters; in 2013, it was 37.1 meters. The water surface coverage increased from 194.9 to 391 km2, flooding agricultural areas and leaving hundreds of people homeless. In addition, salinity increased from 105 ‰ to 23.4 ‰, a decrease of 4.47 times comparable to the volume change, which increased 4.48 times according to topographic and bathymetric maps. These changes began with Tropical Storm Odette and occurred progressively through 15 additional tropical cyclones (TC) or hurricanes that struck Lake Enriquillo between 2003 and 2011. Other climatic phenomena that have great influence on the Caribbean climate include the following: North Atlantic Oscillation (NAO), Southern El Niño Oscillation (ENSO), the trade winds, North Atlantic Warm Pool, Multidecadal Oscillation, the anticyclone Caribbean Regulator Climate Centers (CRCCs), and the Bermuda-Azores High (Mendez-Tejeda et al. 2017). The sediment records deposited by the runoff from these phenomena were analyzed. These proxy records were used to determine the decadal fluctuations related to cyclonic systems and the resultant effect upon increasing the level of Lake Enriquillo (LE). The accumulation rate (TAS) was estimated by means of 210 (210Pb) lead radiochronology, elemental composition, and mineral and ignition loss. These results were correlated with the extreme climatic events that affected the Lake Enriquillo Basin (LEB) from 1900 and 2011.

Deconstructing Global Temperature Anomalies: An Hypothesis

This paper evaluates contributions to global temperature anomalies from greenhouse gas concentrations and from a source of natural variability. There is no accepted causation for the apparent interrelationships between multidecadal oscillations and regime changes in atmospheric circulation, upwelling, and the slowdowns in global surface temperatures associated with a ~60-year oscillation. Exogenous tidal forcing is hypothesized as a major causal agent for these elements, with orthogonal components in tidal forcing generating zonal and meridional regime-dependent processes in the climate system. Climate oscillations are simulated at quasi-biennial to multidecadal timescales by tidal periodicities determined by close approaches of new or full moon to the earth. Subtracting a tidal analog of the ~60-year oscillation from global mean surface temperatures reveals an exponential component comparable with greenhouse gas emission scenarios, and which is responsible for almost 90% or contemporary global temperature increases. Residual subdecadal temperature anomalies correlate with the subdecadal variability of evolved carbon dioxide (CO2), ENSO activity and tidal components, and indicate a causal sequence from tidal forcing to greenhouse gas (GHG) release to temperature increase. Tidal periodicities can all be expressed in terms of four fundamental frequencies. Because of the potential importance of this formulation, tests are urged using general circulation models.