Nudibranchs out of water: long-term temporal variations in the abundance of two Dendrodoris species under emersion

Long-term climate change may strongly affect the aquatic environment in mid-latitude water resources. In particular, it can be demonstrated that temporal variations in surface water temperature in a reservoir have strong responses to air temperature. We adopted deep neural networks (DNNs) to understand the long-term relationships between air temperature and surface water temperature, because DNNs can easily deal with nonlinear data, including uncertainties, that are obtained in complicated climate and aquatic systems. In general, DNNs cannot appropriately predict unexperienced data (i.e., out-of-range training data), such as future water temperature. To improve this limitation, our idea is to introduce a transfer learning (TL) approach. The observed data were used to train a DNN-based model. Continuous data (i.e., air temperature) ranging over 150 years to pre-training to climate change, which were obtained from climate models and include a downscaling model, were used to predict past and future surface water temperatures in the reservoir. The results showed that the DNN-based model with the TL approach was able to approximately predict based on the difference between past and future air temperatures. The model suggested that the occurrences in the highest water temperature increased, and the occurrences in the lowest water temperature decreased in the future predictions.

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CO2 dynamics and heterogeneity in a cave atmosphere: role of ventilation patterns and airflow pathways

Theoretical and Applied Climatology ◽

10.1007/s00704-021-03722-w ◽

2021 ◽

Author(s):

Lovel Kukuljan ◽

Franci Gabrovšek ◽

Matthew D. Covington ◽

Vanessa E. Johnston

Keyword(s):

Temporal Variations ◽

Observation Point ◽

Spatially Distributed ◽

Combined Action ◽

Karst Systems ◽

The Relationship ◽

Co2 Dynamics ◽

Global Carbon

AbstractUnderstanding the dynamics and distribution of CO2 in the subsurface atmosphere of carbonate karst massifs provides important insights into dissolution and precipitation processes, the role of karst systems in the global carbon cycle, and the use of speleothems for paleoclimate reconstructions. We discuss long-term microclimatic observations in a passage of Postojna Cave, Slovenia, focusing on high spatial and temporal variations of pCO2. We show (1) that the airflow through the massif is determined by the combined action of the chimney effect and external winds and (2) that the relationship between the direction of the airflow, the geometry of the airflow pathways, and the position of the observation point explains the observed variations of pCO2. Namely, in the terminal chamber of the passage, the pCO2 is low and uniform during updraft, when outside air flows to the site through a system of large open galleries. When the airflow reverses direction to downdraft, the chamber is fed by inlets with diverse flow rates and pCO2, which enter via small conduits and fractures embedded in a CO2-rich vadose zone. If the spatial distribution of inlets and outlets produces minimal mixing between low and high pCO2 inflows, high and persistent gradients in pCO2 are formed. Such is the case in the chamber, where vertical gradients of up to 1000 ppm/m are observed during downdraft. The results presented in this work provide new insights into the dynamics and composition of the subsurface atmosphere and demonstrate the importance of long-term and spatially distributed observations.

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Autogenic versus allogenic controls on the evolution of a coupled fluvial megafan/mountainous catchment system: numerical modelling and comparison with the Lannemezan megafan system (Northern Pyrenees, France)

10.5194/esurf-2016-44 ◽

2016 ◽

Cited By ~ 2

Author(s):

Margaux Mouchené ◽

Peter van der Beek ◽

Sébastien Carretier ◽

Frédéric Mouthereau

Keyword(s):

Numerical Modelling ◽

Temporal Variations ◽

Tectonic Activity ◽

Mountain Range ◽

Stream Network ◽

Mountainous Catchment ◽

Isostatic Rebound ◽

Base Level ◽

Alluvial Terraces

Abstract. Alluvial megafans are sensitive recorders of landscape evolution, controlled by autogenic processes and allogenic forcing and influenced by the coupled dynamics of the fan with its mountainous catchment. The Lannemezan megafan in the northern Pyrenean foreland was abandoned by its mountainous feeder stream during the Quaternary and subsequently incised, leaving a flight of alluvial terraces along the stream network. We explore the relative roles of autogenic processes and external forcing in the building, abandonment and incision of a foreland megafan using numerical modelling and compare the results with the inferred evolution of the Lannemezan megafan. Autogenic processes are sufficient to explain the building of a megafan and the long-term entrenchment of its feeding river at time and space scales that match the Lannemezan setting. Climate, through temporal variations in precipitation rate, may have played a role in the episodic pattern of incision at a shorter time-scale. In contrast, base-level changes, tectonic activity in the mountain range or tilting of the foreland through flexural isostatic rebound appear unimportant.

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The impact of non-ideality on reconstructing spatial and temporal variations of aerosol acidity with multiphase buffer theory

10.5194/egusphere-egu21-9292 ◽

2021 ◽

Author(s):

Yafang Cheng ◽

Guangjie Zheng ◽

Hang Su ◽

Siwen Wang ◽

Andrea Pozzer

Keyword(s):

Molar Fraction ◽

Temporal Variations ◽

Spatial Variations ◽

Acid Dissociation ◽

Acid Dissociation Constant ◽

Aerosol Acidity ◽

Long Term Trends ◽

Factor C ◽

The Impact

Aerosol acidity is a key parameter in atmospheric aqueous chemistry and strongly influence the interactions of air pollutants and ecosystem. The recently proposed multiphase buffer theory provides a framework to reconstruct long-term trends and spatial variations of aerosol pH based on the effective acid dissociation constant of ammonia (Ka,NH3*). However, non-ideality in aerosol droplets is a major challenge limiting its broad applications. Here, we introduced a non-ideality correction factor (cni) and investigated its governing factors. We found that besides relative humidity (RH) and temperature, cni is mainly determined by the molar fraction of NO3- in aqueous-phase anions, due to different NH4+ activity coefficients between (NH4)2SO4- and NH4NO3-dominated aerosols. A parameterization method is thus proposed to estimate cni at given RH, temperature and NO3- fraction, and is validated against long-term observations and global simulations. In the ammonia-buffered regime, with cni correction the buffer theory can well reproduce the Ka,NH3* predicted by comprehensive thermodynamic models, with root-mean-square deviation ~0.1 and correlation coefficient ~1. Note that, while cni is needed to predict Ka,NH3* levels, it is usually not the dominant contributor to its variations, as ~90% of the temporal or spatial variations in Ka,NH3* is due to variations in aerosol water and temperature.

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Long-term temporal changes in the occurrence of a high forest fire danger in Finland

Natural Hazards and Earth System Science ◽

10.5194/nhess-12-2591-2012 ◽

2012 ◽

Vol 12 (8) ◽

pp. 2591-2601 ◽

Cited By ~ 6

Author(s):

H. M. Mäkelä ◽

M. Laapas ◽

A. Venäläinen

Keyword(s):

Forest Fire ◽

Forest Fires ◽

Large Scale ◽

Weather Conditions ◽

Temporal Variations ◽

Fire Danger ◽

Specific Information ◽

Climate Data ◽

Forest Fire Danger

Abstract. Climate variation and change influence several ecosystem components including forest fires. To examine long-term temporal variations of forest fire danger, a fire danger day (FDD) model was developed. Using mean temperature and total precipitation of the Finnish wildfire season (June–August), the model describes the climatological preconditions of fire occurrence and gives the number of fire danger days during the same time period. The performance of the model varied between different regions in Finland being best in south and west. In the study period 1908–2011, the year-to-year variation of FDD was large and no significant increasing or decreasing tendencies could be found. Negative slopes of linear regression lines for FDD could be explained by the simultaneous, mostly not significant increases in precipitation. Years with the largest wildfires did not stand out from the FDD time series. This indicates that intra-seasonal variations of FDD enable occurrence of large-scale fires, despite the whole season's fire danger is on an average level. Based on available monthly climate data, it is possible to estimate the general fire conditions of a summer. However, more detailed input data about weather conditions, land use, prevailing forestry conventions and socio-economical factors would be needed to gain more specific information about a season's fire risk.

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Long-term temporal variations and source changes of halocarbons in the Greater Pearl River Delta region, China

Atmospheric Environment ◽

10.1016/j.atmosenv.2020.117550 ◽

2020 ◽

Vol 234 ◽

pp. 117550 ◽

Cited By ~ 2

Author(s):

Lewei Zeng ◽

Juan Dang ◽

Hai Guo ◽

Xiaopu Lyu ◽

Isobel J. Simpson ◽

...

Keyword(s):

Pearl River Delta ◽

Temporal Variations ◽

River Delta ◽

Pearl River ◽

Pearl River Delta Region ◽

Delta Region

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Long-term dynamics of natural populations of Schistosoma mansoni among Rattus rattus in patchy environment

Parasitology ◽

10.1017/s0031182000061734 ◽

1992 ◽

Vol 104 (2) ◽

pp. 291-298 ◽

Cited By ~ 40

Author(s):

A. Théron ◽

J. P. Pointier ◽

S. Morand ◽

D. Imbert-Establet ◽

G. Borel

Keyword(s):

Schistosoma Mansoni ◽

Rattus Rattus ◽

Natural Populations ◽

Ecological Factors ◽

Temporal Variations ◽

Distribution Analysis ◽

Patchy Environment ◽

Human Parasite ◽

Spatio Temporal

SUMMARYDynamics of natural populations of Schistosoma mansoni were studied during 8 consecutive years among Rattus rattus populations from 8 transmission sites of the marshy forest focus of Guadeloupe (French West Indies). The schistosome population is over-dispersed (k = 0·119) within the murine hosts and ecological factors linked to the patchy environment may be responsible for such aggregated distribution. Analysis of the spatio-temporal variations in prevalences, intensities and abundances showed limited variations of the infection during the 8 years at the level of the whole parasite population but great spatial heterogeneity at the level of local schistosome populations. Inter-populational genetic variability linked to the degree of adaptation of this human parasite to the murine host may explain differences in transmission dynamics between the local populations of S. mansoni.

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Long-term population trends of the Red-legged CormorantPhalacrocorax gaimardion the Argentine coast

Bird Conservation International ◽

10.1017/s0959270914000094 ◽

2014 ◽

Vol 25 (2) ◽

pp. 234-241 ◽

Cited By ~ 2

Author(s):

ANA MILLONES ◽

PATRICIA GANDINI ◽

ESTEBAN FRERE

Keyword(s):

Population Change ◽

Breeding Population ◽

Temporal Variations ◽

Population Trends ◽

World Population ◽

Ocean Productivity ◽

Marine Primary Productivity ◽

Long Term Trend ◽

Positive Effect

SummaryThe world population of Red-legged CormorantPhalacrocorax gaimardiis reasonably small and has showed rapid declines. In Argentina, this species breeds in 13 localities and is considered as ‘Endangered’ by the national government. In this study, we provide information about population trends of the Red-legged Cormorant on the Argentine coast, between 1990 and 2009. We also discuss whether these trends could be related to sea surface temperature and marine primary productivity, both of which are considered oceanographic factors that can affect breeding seabirds. The long-term trend in the breeding population showed a slight decrease of 1.2% per year. Seven colonies showed an average population change < 1. Periods of stability and increase were identified over the study period, but they were insufficient to compensate for the decreases. The largest colony of Red-legged Cormorants (La Mina, with more than 55% of the entire breeding population) seems to determine the overall population trend. We did not find a direct relationship between the overall number of Red-legged Cormorants and the two oceanographic factors analysed. However, our analysis detected a positive effect of ocean productivity close to the coast on the largest colony at the beginning of the breeding season, suggesting that coastal ocean productivity could be an important factor affecting temporal variations in the Argentinian population.

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Oxygen isotope composition of the Phanerozoic ocean and a possible solution to the dolomite problem

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1719681115 ◽

2018 ◽

Vol 115 (26) ◽

pp. 6602-6607 ◽

Cited By ~ 28

Author(s):

Uri Ryb ◽

John M. Eiler

Keyword(s):

Oxygen Isotope ◽

Isotope Exchange ◽

Isotope Composition ◽

Temporal Variations ◽

Oxygen Isotope Exchange ◽

Diagenetic Alteration ◽

Isotope Studies ◽

Dolomite Problem ◽

Clumped Isotope

The18O/16O of calcite fossils increased by ∼8‰ between the Cambrian and present. It has long been controversial whether this change reflects evolution in the δ18O of seawater, or a decrease in ocean temperatures, or greater extents of diagenesis of older strata. Here, we present measurements of the oxygen and ‟clumped” isotope compositions of Phanerozoic dolomites and compare these data with published oxygen isotope studies of carbonate rocks. We show that the δ18O values of dolomites and calcite fossils of similar age overlap one another, suggesting they are controlled by similar processes. Clumped isotope measurements of Cambrian to Pleistocene dolomites imply crystallization temperatures of 15–158 °C and parent waters having δ18OVSMOWvalues from −2 to +12‰. These data are consistent with dolomitization through sediment/rock reaction with seawater and diagenetically modified seawater, over timescales of 100 My, and suggest that, like dolomite, temporal variations of the calcite fossil δ18O record are largely driven by diagenetic alteration. We find no evidence that Phanerozoic seawater was significantly lower in δ18O than preglacial Cenozoic seawater. Thus, the fluxes of oxygen–isotope exchange associated with weathering and hydrothermal alteration reactions have remained stable throughout the Phanerozoic, despite major tectonic, climatic and biologic perturbations. This stability implies that a long-term feedback exists between the global rates of seafloor spreading and weathering. We note that massive dolomites have crystallized in pre-Cenozoic units at temperatures >40 °C. Since Cenozoic platforms generally have not reached such conditions, their thermal immaturity could explain their paucity of dolomites.

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