Insolation Fluctuations Research Articles

Phenotypic Variance Predicts Symbiont Population Densities in Corals: A Modeling Approach

BackgroundWe test whether the phenotypic variance of symbionts (Symbiodinium) in corals is closely related with the capacity of corals to acclimatize to increasing seawater temperatures. Moreover, we assess whether more specialist symbionts will increase within coral hosts under ocean warming. The present study is only applicable to those corals that naturally have the capacity to support more than one type of Symbiodinium within the lifetime of a colony; for example, Montastraea annularis and Montastraea faveolata. Methodology/Principal FindingsThe population dynamics of competing Symbiodinium symbiont populations were projected through time in coral hosts using a novel, discrete time optimal–resource model. Models were run for two Atlantic Ocean localities. Four symbiont populations, with different environmental optima and phenotypic variances, were modeled to grow, divide, and compete in the corals under seasonal fluctuations in solar insolation and seawater temperature. Elevated seawater temperatures were input into the model 1.5°C above the seasonal summer average, and the symbiont population response was observed for each location. The models showed dynamic fluctuations in Symbiodinium populations densities within corals. Population density predictions for Lee Stocking Island, the Bahamas, where temperatures were relatively homogenous throughout the year, showed a dominance of both type 2, with high phenotypic variance, and type 1, a high-temperature and high-insolation specialist. Whereas the densities of Symbiodinium types 3 and 4, a high-temperature, low-insolation specialist, and a high-temperature, low-insolation generalist, remained consistently low. Predictions for Key Largo, Florida, where environmental conditions were more seasonally variable, showed the coexistence of generalists (types 2 and 4) and low densities of specialists (types 1 and 3). When elevated temperatures were input into the model, population densities in corals at Lee Stocking Island showed an emergence of high-temperature specialists. However, even under high temperatures, corals in the Florida Keys were dominated by generalists.Conclusions/SignificancePredictions at higher seawater temperatures showed endogenous shuffling and an emergence of the high-temperature Symbiodinium specialists, even though their phenotypic variance was low. The model shows that sustaining these “hidden” specialists becomes advantageous under thermal stress conditions, and shuffling symbionts may increase the corals' capacity to acclimatize but not adapt to climatechange–induced ocean warming.

Hydrogen production characteristics of a bioethanol solar reforming system with solar insolation fluctuations

Abstract The development of a bioethanol steam reforming system (FBSR) is considered as a means of distributing energy using PEM fuel cells. Small-scale solar collectors (collection areas on the order of several m 2 ) are installed in a house as a method for applying the FBSR. However, the temperature distribution of a reforming catalyst fluctuates under conditions of unstable solar insolation. Therefore, heat transfer analysis applied in reforming the catalyst layer of the reactor and the temperature distribution and transient response characteristics of the gas composition of the process were investigated. As a case study, meteorological data for representative days in March and August in Sapporo, Japan were recorded, and the hydrogen production speed, power generation output and amount of electricity purchased were analyzed. The results showed that although fluctuations in solar insolation affected the efficiency of the FBSR, the average efficiency of each representative day exceeded 40%. By installing two solar collectors, each with a collection area of 1 m 2 , 21–25% of the average power demand of an individual house can be supplied.

Study on a Bioethanol Solar Reforming System with the Solar Insolation Fluctuation in Consideration of Heat Chemical Reaction

Study on a Bioethanol Solar Reforming System with the Solar Insolation Fluctuation in Consideration of Heat Chemical Reaction

Estimation of the total cloud cover with high temporal resolution and parametrization of short-term fluctuations of sea surface insolation

Sky observations by means of digital full sky imagers enable a continuous monitoring and archiving of the state of the atmosphere. A direct application is the estimation of the total amount of clouds with a very high temporal resolution. From simple methods of image analysis, we used the full sky imager additionally as a sunshine recorder to replace complex pyrheliometric and pyranometric measurements for detecting direct solar irradiation. The Meridional Ocean Radiation Experiment MORE has realized four transatlantic research cruises with a special focus on the surface radiation budget, remote sensing of clouds and automated sky monitoring. This dataset was used to study different parametrizations of solar downward radiation at the sea surface based on standard meteorological measurements. It was found that the parameterization by ZILLMAN (1972) provided the best performance for the use with operational meteorological data. Furthermore, this parametrization was modified to create a fast responding parametrization to reproduce short-term fluctuations of the insolation. This new parametrization has been applied to independent datasets. It is shown that based on measurements of a few weeks it was not possible to reduce the overall bias of parameterized insolation significantly due to the fact that the parametrization does not consider the optical thickness of clouds. The standard deviation between calculated and measured flux has been reduced by 4%. The performance for separated broken cloud conditions was improved significantly.

Timing and nature of late Quaternary mountain glaciation

AbstractCompilations of regional‐ to subcontinental‐scale mountain glacier chronologies from five continents, plus Hawaii, examine the temporal and spatial patterns of mountain glaciation. The compilations yield key insights into the nature of past fluctuations in temperature and precipitation in mountains and adjacent regions, and provide baseline data for examining the dynamics of glacier responses to climate change. Key insights from these compilations include the wide variability of glacier responses to fluctuations in insolation, temperature and precipitation and the regionally specific variations in climatic variables through late Quaternary time. The compilations highlight the need to improve the density and quality of geochronological data and to enhance the understanding of the links between climate and glaciation. Copyright © 2008 John Wiley & Sons, Ltd.

Quantitative tests for stratigraphic cyclicity

AbstractPeriodic Milankovitch (M‐) orbital forcing provides an explanation for subjectively recognized short‐term repetition of lithofacies‐‘cycles’‐in the stratigraphic record. Tests of this explanation often find no order in the lithofacies and/or no regularity in the recurrence of lithofacies. This does notdisprovethe influence of M‐forcing, but a sedimentary response in terms ofirregularM‐forced ‘cycles’ is indistinguishable from one in which repetition of facies is not M‐forced. Use of such cycles in time calibration is correspondingly suspect. Stricter,dimensionalcyclicity invokes Sander's Rule, which suggests periodicity in sedimentation, for which M‐forcing provides an obvious explanation. Time calibration on the basis of strict cyclicity thus appears more dependable. Objective tests for regular M‐forced stratigraphic cyclicity commonly depend upon spectral analyses. Such tests are not unambiguous. Bilogarithmic thickness/frequency plots derived from objective layer thickness inventories (LTI) provide an alternative. Commonly, such plots show power‐law relationships that preclude dimensional M‐cyclicities. By contrast, a model data series that perfectly encodes the M‐cyclic fluctuations in terrestrial insolation generates a strongly inflected, non‐power‐law LTI plot. Power‐law plots result where the model data series is decimated by random hiatuses, with numbers and durations tuned to M‐cycle frequencies. It seems improbable that natural data series record such tuning. The general absence of strict cyclicity in the M‐frequency range is more likely to reflect the nonlinear response of sedimentary systems to cyclic M‐forcing of insolation. Interestingly, when applied to the classically cyclic lacustrine Triassic sediments of the Newark Basin, USA, the LTI test suggests a decimated record, preserving some evidence of M‐cyclicity. Copyright © 2008 John Wiley & Sons, Ltd.

Sensitivity of the diurnal warm layer to meteorological fluctuations part 1: observations

Sea surface temperature (SST) is directly affected by the diurnal cycle of the sun's radiation. Over 200 cases of diurnal cycles of SST are analysed in conjunction with their associated meteorological fields to investigate the phase of the diurnal SST cycle and understand the sensitivity of the diurnal warm layer to meteorological variability during the day. A classification is presented which categorises diurnal warming shapes into four separate groups based on different wind and insolation fluctuations. Differences between the shape of the diurnal signal at the surface and depth are investigated in order to interpret the diurnal variations detected by satellite and in situ measurement techniques. The results highlight the variability in the shape of the diurnal SST cycle and draw attention to the large differences in temperature that can occur between the surface and 1 m under low wind and strong heating conditions. This is important for air–sea heat and gas exchange as the diurnal temperature variation...

Sensitivity of the diurnal warm layer to meteorological fluctuations. Part 2: A new parameterisation for diurnal warming

A new diurnal warming parameterisation has been developed which allows the shape of the diurnal sea surface temperature (SST) signal to change in response to meteorological fluctuations during the day based on an extensive examination of over 300 diurnal cycles. The parameterisation estimates the diurnal variation in temperature at the surface and at 1 m over a local day based only on wind and insolation measurements averaged over several different periods of the day. The parameterisation is validated against independent data and is compared against other existing parameterisations. Results show that diurnal warming estimates are more accurate when daily fluctuations in wind and insolation are taken into consideration and the new parameterisation captures some of the variability of the shape of the diurnal SST cycle which other parameterisations are unable to achieve. The parameterisation is currently being trialled in the European Space Agency MEDSPIRATION project (a contribution to the Global Ocean Data...

Carbonate Composite Catalyst with High-Temperature Thermal Storage for Use in Solar Tubular Reformers

The composite materials of Ni-applied, porous zirconia balls with molten Na2CO3 salt were examined for use in solar thermochemical reforming of methane as the catalyst with high-temperature thermal storage. The millimeter-sized composite balls were tested on the heat discharge property and the catalytic activity for CO2 reforming of methane in a laboratory-scale reactor. The high heat capacity and large latent heat (heat of solidification) of the composite molten salt circumvented the temperature dropping of the catalyst bed, which resulted in the alleviation of rapid decay in chemical conversion during cooling mode of the reactor. The composite catalyst is expected to realize stable operation in the solar reformer under fluctuation of insolation by a cloud passage.

Early Maastrichtian stable isotopes: changing deep water sources in the North Atlantic?

We propose that the observed short-term stable isotope fluctuations reflect changes in high- and low-latitude intermediate to deep water sources, based on a high-resolution stable isotope record of planktic and benthic foraminifera from the Early Maastrichtian (∼71.3 to ∼69.6 Ma) of Blake Nose (DSDP Site 390A, North Atlantic). Sources of these waters may have been the low-latitude eastern Tethys and high-latitude North Atlantic. Changes in intermediate to deep water sources were probably steered by eccentricity-controlled insolation fluctuations. Lower insolation favored the formation of high-latitude deep waters due to positive feedback mechanisms resulting in high-latitude cooling. This led to a displacement of low-latitude deep waters at Blake Nose. Higher insolation reduced intermediate to deep-water formation in high latitudes, yielding a more northern flow of low-latitude deep waters.

Early Maastrichtian stable isotopes: changing deep water sources in the North Atlantic?

We propose that the observed short-term stable isotope fluctuations reflect changes in high- and low-latitude intermediate to deep water sources, based on a high-resolution stable isotope record of planktic and benthic foraminifera from the Early Maastrichtian (∼71.3 to ∼69.6 Ma) of Blake Nose (DSDP Site 390A, North Atlantic). Sources of these waters may have been the low-latitude eastern Tethys and high-latitude North Atlantic. Changes in intermediate to deep water sources were probably steered by eccentricity-controlled insolation fluctuations. Lower insolation favored the formation of high-latitude deep waters due to positive feedback mechanisms resulting in high-latitude cooling. This led to a displacement of low-latitude deep waters at Blake Nose. Higher insolation reduced intermediate to deep-water formation in high latitudes, yielding a more northern flow of low-latitude deep waters.

Ecological collapse of Lake Baikal and Lake Hovsgol ecosystems during the Last Glacial and consequences for aquatic species diversity

Sedimentary sections from Lake Baikal in Siberia and Lake Hovsgol in Mongolia show that during the Last Glacial Maximum (LGM), planktonic/benthic diatoms, chrysophyte cysts, sponge spicules and zooplankton remains did not accumulate in the lake sediments. The combined data suggest a drastic lowering of photosynthetic production and perhaps the collapse of the ecosystems of both lakes due to significant environmental changes during the LGM. Both lakes were almost uninhabited during the LGM. Starting from ∼12,000 to 13,000 14C years ago, the planktonic communities redeveloped and primary production increased in both lakes. As a result, Holocene sediments contain abundant and well-preserved planktonic/benthic diatoms, stomatocysts, sponge spicules and zooplankton remains. The ecosystem stress in Lake Baikal during glacial time appears to be due to a decrease in nutrient loading from the watershed, lowering of surface water temperature, and very low transparency of water and ice. We believe that endemic species in Baikal survived during glacial ecological catastrophes in refugia that could have been a source of species that invaded and repopulated Baikal after intense and long glacial winters. The ecosystem stress in Lake Hovsgol during glacial time appears to be due primarily to drastic lake level falls, and changes in water chemistry. At the beginning of the Holocene, Lake Hovsgol was reoccupied again by cosmopolitan species probably from surrounding small lakes and rivers. In addition to the LGM results, we also show that Lake Baikal planktonic diatom species diversity during the last 350 ka is closely related to solar insolation fluctuations caused by the 23 and 41 ka cycles of the Earth's precession and obliquity. Our results also indicate that Baikal's planktonic diatom species diversity, as measured by the Shannon–Weiner index, correlates with the oxygen isotope record that represents changes in global ice volume.

PVシステムのMPPT制御特性の調整による出力平準化

A PV system’s output is not stable and fluctuates depending on a weather condition. Using a battery is one of the feasible ways to stabilize a PV system’s output, although it requires an additional cost and provides an additional waste of the used battery. In this paper, we propose tuning a characteristic of Maxiumum Power Point Tracking (MPPT) control for smoothing a short term change of PV system’s output during a sharp insolation fluctuation, as an approach without additional equipments. In our proposed method, when an insolation increases rapidly, the operation point of MPPT control changes to the new point where the maximum power is not generated with present insolation, so that the speed of PV system’s output increase is limited to a certain value, i. e. 1%/min. In order to evaluate the effect of our proposed method in terms of reducing the additional operation task of the electric power system, we evaluated the additional LFC capacity for a large-scale installation of PV systems. As a result, it was revealed that the additional LFC capacity is not required even if a PV system is installed by 5% of utility system, when our proposed method is applied to all PV systems.

Ni/ceramic/molten-salt composite catalyst with high-temperature thermal storage for use in solar reforming processes

Composite materials of catalytically activated porous ceramics with molten salts were proposed for use in solar thermochemical reforming processes of methane as catalyst with high-temperature thermal storage. The high heat capacity and large latent heat (heat of solidification) of the composite molten salt at high temperatures are expected to circumvent the rapid temperature change of the catalyst bed under fluctuation of insolation. The composite catalysts of Ni-activated porous ceramics (mm-sized alumina or zirconia balls) with an alkali-metal chloride or carbonate (NaCl or Na 2CO 3) were prepared and examined for the activity and stability for CO 2 reforming of methane.

CO2 Reforming of Methane in a Molten Carbonate Salt Bath for Use in Solar Thermochemical Processes

CO2 reforming of methane was studied by bubbling a CH4/CO2 mixture in a molten salt bath of alkali-metal carbonate mixture (Na2CO3/K2CO3) containing suspended metal catalyst powder at 1223 K. Ni, Fe, Cu, or W metals, supported on an Al2O3 support, were examined for activity and selectivity. The most active and selective catalyst was the Ni/Al2O3 catalyst. The methane conversion increased with an increase in the W/F ratio (W = weight of the molten salt bath containing the Ni/Al2O3 catalyst, and F = flow rate of CH4/CO2 mixture). About 70% of methane conversion was obtained at a W/F ratio of 0.25 g min cm-3, in which the H2/CO ratio in the product gas was approximately the stoichiometric ratio of one. This technique will be applied to the solar thermochemical methane reforming for converting solar high-temperature heat to chemical fuels, to give stable operations under fluctuation of insolation and thermal uniformity in the solar reformer under concentrated solar irradiation.

Multifactorial control on deposition of epicontinental hemi-pelagic carbonates during the earliest Kimmeridgian (Prebetic Zone, southern Spain)

Two successions of marly limestone–limestone couplets, occasionally with significant intercalations of marls, have been investigated in the lower Kimmeridgian (Platynota Zone) in the central sector of the Prebetic Zone (southern Spain). The aim of this paper is to identify and evaluate possible interactions between global signals (orbital fluctuations, climate and eustasy) and local–regional tectonics forcing deposition and ecospace on an epicontinental shelf. High-resolution ammonite biostratigraphy, together with sedimentological, stratigraphical, mineralogical data, and ecostratigraphic interpretations, were re-examined to provide evidence for the combined action of tectonics, eustasy and insolation fluctuations on sedimentation in two sections which clearly differ in stratal pattern, both in the average thickness of limestone beds and in the frequency and character of marl intercalations. The detailed analysis of stratal patterns was used to identify and calibrate the influence of the different factors investigated. The identification of significant bedding planes in the sections studied enabled the recognition of eight bundles of beds (major cycles). The analysis and comparison of their internal structure, together with the information about tectonic and eustatic influences, enabled us to interpret the lower part of the sections (bundles 1 and 2) as being forced by interactions between orbital signals and tectonics, the upper part (bundles 6, 7 and 8) as being caused by interactions between orbital signals and eustasy, and the middle part (bundles 3, 4 and 5) as being related mainly to orbital forcing.

Lake Qinghai, China: closed-basin like levels and the oxygen isotope record for ostracoda since the latest Pleistocene

In 1985 a Sino-Swiss limnogeological expedition to China's largest inland lake recovered seismic profiles and piston cores to help calibrate palaeoclimatic models of monsoon and insolation fluctuations over the northern Tibet-Qinghai Plateau since the Last Glacial Maximum. Lake Qinghai, a perennial lake with an area of 4278 km 2 (1985) at 3194 m above sea level, receives drainage from 30,000 km 2 of catchment near the northwest corner of the Plateau. The 26.5 m deep terminal lake (1985), with brackish, alkaline, magnesium-sulphate rich waters (14 g 1 −1 TDS), has not overflowed since the last Glacial, but its levels have responded to climatic and hydrologic changes. Seismic-reflection profiles for the sub-bottom sediment structures revealed a complex topography with channels, relict terraces, tectonic tilting and deformation in deposits buried under a 4–6 m packet of mainly flat-bedded sediments from which core samples were recovered. The lowermost cored material (≈14,500 yr B.P.) comprises mainly water-lain loess deposited in a smaller flood-plain lake of up a few metres depth under cold arid climatic conditions. AMS radiocarbon dating indicates average sedimentation rates for latest Pleistocene and Holocene deposits in central basin regions of ≈0.3–0.5 mm yr −1. The δ 18O values of fossil ostracod valves provide a record of changes in the isotopic chemistry of the lake waters that can be related to the precipitation: evaporation budgets which have controlled the palaeo-levels for Lake Qinghai. The precipitation/evaporation budget for the Lake Qinghai region is largely determined by the Asian monsoon system. The Lake Qinghai sediment record shows that there was no large influx of glacoer melt-waters into the lake basin during the post-Glacial. The regional climate remained arid until at least ≈ 12,500 yr B.P., when an incipient monsoon was possibly initiated. River-transported silts first reached the basin centre at ≈11,800 yr B.P., when the lake depth may have increased to ≈ 5 m. Possibly a monsoonal weakening for several centuries after ≈ 10,800 yr B.P. (Europe, Younger Dryas) caused a further period of aridity. At ≈ 10,200 yr B.P. the basin began filling towards modern lake dimensions in response to a permanent strengthening of the Asian monsoon. Substantial lake-level rises probably characterised the periods ≈ 10,200-9800, 9500-8500, 8300-7200 yr B.P. and through perhaps a century at about 6800 yr B.P. Decreasing levels probably characterised the intervening intervals. Short-term lake-level fluctuations through the mid-Holocene climatic optimum were minimal, indicating a very stable climatic / hydrologic regime. An isotopic steady-state for the lake waters since 3000 ± 500 yr B.P. obscures the climatic / hydrologic regime dependent δ 18O gradient, but there is little stratigraphic evidence to suggest that the lake level has been significantly below its present level since that time. Three negative δ 18O excursions for the lake waters may correspond to known glacier advances on the Plateau at ≈3000, 2000 and 1500 yr B.P. during China's neoglacial.

Diurnal efficiency at mid latitudes of solar collectors with various thermal capacitances

A verified, multi-node computer model of a flat-plate, rear-duct, air-heating solar collector is described. Results are presented of the daily averaged thermal efficiencies for a variety of simulated ambient conditions pertinent to mid maritime latitudes, for a range of collectors that differ in their thermal capacitances. The smooth, diurnal cycle of insolation produces a significant spread of thermal efficiencies among the collectors, indicating that simple, approximate models of flat-plate collectors might lead to significant errors in predicting performance in real conditions. Rapid fluctuations in insolation, superimposed on the diurnal cycle, lead to only a slightly greater spread of thermal efficiencies. The effect of thermal capacitance on air outlet temperatures is slight.

Late Pliocene climatic change and the onset of Northern Hemisphere glaciation as recorded in the northeast Atlantic Ocean

The relative abundances of planktonic Foraminifera, oxygen-isotope values of benthic Foraminifera, and the sedimentology of 156 samples from Deep Sea Drilling Project–International Phase of Ocean Drilling Site 548 in the northeast Atlantic Ocean, have been analyzed for the time span from about 3.5 to 2.0 m.y. B.P. The planktonic assemblage at Site 548 in the late Pliocene consisted mainly of subpolar to temperate species; warm-water species were rare. The planktonic record shows that waters in the northeast Atlantic were warm-temperate before 3.4 m.y. ago and gradually changed to subpolar, through a series of steps, by 2.0 m.y. B.P. An initial cooling event occurred between about 3.4 and 3.1 m.y. B.P. The beginning of this cooling event preceded the global benthic isotopic shift at 3.2 to 3.1 m.y. B.P., but the isotopic shift correlates to a marked change in the planktonic assemblage, suggesting that the cause of the shift also affected northeast Atlantic surface circulation. Following the 3.4 to 3.1 m.y. B.P. cooling event, the assemblages at Site 548 indicate a return of temperate waters. At this time, however, the assemblages also became quite variable with a clear cyclicity. From about 2.6 m.y. B.P. onward, there is a progressive cooling recorded at Site 548, leading to marked glaciations beginning at about 2.4 m.y. B.P. About 2.0 m.y. B.P. the planktonic assemblages were dominated by cold-water species and became quite stable, contrasting markedly with the immediately preceding interval of glaciation and extreme variability. The cyclicity seen in the faunal data after about 3.1 m.y. B.P. is principally of one period, with a cycle length closest to that of the Earth9s obliquity and its influence on global insolation. The effect of obliquity on the Earth9s insolation is most strongly felt at high latitudes, and so the cyclicity at Site 548 indicates that conditions in the Arctic have exerted an influence on the northeast Atlantic since at least 3 m.y. ago. Calculation of global insolation fluctuations for the late Pliocene shows that the major changes in the planktonic record at Site 548 cannot be explained by insolation variation, except for the period of stability at 2.0 m.y. B.P., which corresponds to a time of stable insolation. The planktonic data, however, do contain cyclicity that can be related to the periodicity of the Earth9s orbital elements.

Litter Fall of Avicennia germinans L. in a One-Year Cycle in a Mudflat at the Laguna de Mecoacan, Tabasco, Mexico

The fall of four morphological components of Avicennia germinans L. was measured at monthly intervals along a transect in a monospecific mangrove near the inlet of the Laguna de MecoacAn, Tabasco, Mexico. Estimated mean total annual litter fall was 614.4 g.m-2 yr-1. Seasonal fluctuations of mean water level, insolation, temperature and evaporation were highly intercorrelated and were summarized in a principal component axis that explains 82 percent of their variability. The results suggest that litter fall in A. germinans responds to the environmental variables already mentioned but is statistically independent from local rainfall. Each litter component (leaves, flowers and reproductive parts, branches and woody parts, and propagules) shows a distinctive sequence, and significant correlations were obtained when comparing the principal component axis against leaf and propagule fall. Phenologic variation in litter fall as an adaptive response to environmental changes is discussed. DESCRIPTIONS OF THE PHENOLOGY OF MANGAL WOODY SPECIES have been done in Florida (Gill and Tomlinson 1971, Pool et al. 1975); Thailand (Christensen 1978, WiumAndersen and Christensen 1978); Malaysia (Gong et al. 1980); Veracruz, Mexico (Rico 1979); and northeastern Australia (Williams et al. 1981). Emphasis, however, has been given in most cases to the whole community, or to species of Rhizophora. Recent reports have made clear that there are different species responses to the mangal environment and dimate (e.g., Wium-Andersen 1981, Williams et al. 1981, Snedaker and Brown 1982). This paper describes the annual phenological variations in litter fall of Avicennia germinans L. in a mudflat environment and analyzes their relation to environmental parameters, such as temperature, insolation, water level, and rainfall.