Ocean Climate Conditions Research Articles

Evolution of ocean circulation and water masses in the Guaymas Basin (Gulf of California) during the last 31,000 years revealed by radiolarians and silicoflagellates in IODP expedition 385 sediment cores

The high-resolution analysis of radiolarians and silicoflagellates in sediments from Holes U1545A and U1549A drilled during IODP Expedition 385 in the Guaymas Basin, in the Gulf of California provides detailed insights into the evolution of ocean circulation and water masses, and its relation to Eastern Tropical Pacific Ocean climate conditions, over the past 31,000 cal years BP (based on AMS radiocarbon dates). In the pre-Last Glacial Maximum, the Guaymas Basin experienced alternating circulation patterns of California Current Water (CCW) and Gulf of California Water (GCW), with an extended presence of the Pacific Intermediate Water (PIW) owing to: amplified jet streams; southern movement of the California Current System (CCS) and the incursion of CCW into the gulf; and increased North Pacific Intermediate Water (NPIW) formation. The Last Glacial Maximum witnessed the incursion of CCW due to the stronger CCS. The dominance of the PIW indicates the expansion and formation of NPIW. The Heinrich-I event as manifested in the core record, displays two distinct patterns, one suggesting GCW-like dominance and the other, the occurrence of CCW. The Bølling-Ållerød interstadial featured the entry of Tropical Surface Water (TSW), GCW, and CCW, linked with the northward migration of the Intertropical Convergence Zone. In the Younger Dryas, CCW dominated, transitioning to GCW as colder climatic conditions and more intense CCS. The Holocene displayed alternating periods of TSW and GCW, with a modern monsoon regime from 7,600 to 1,000 cal years BP. From 1,000 cal years BP to the present the ITCZ shifted to the south.

Understanding the impact of hydrodynamics on coastal erosion in Latin America: a systematic review

Coastal zones in Latin America support a significant regional population and are vital for providing essential ecosystem services that underpin crucial socio economic activities. However, these zones face pressing challenges, with coastal erosion being a prominent concern. Coastal erosion not only jeopardizes coastal stability but also leads to occasional loss of natural habitats. This is particularly worrisome for sandy beaches due to the consistent shoreline retreat in specific regions. Short term adverse effects of coastal erosion are often attributed to human activities. Nonetheless, the influence of hydrodynamic processes, intensified by extreme events, is gaining prominence. This is due to the combined impact of tides, waves, currents, and other factors, resulting in accelerated shoreline retreat and significant losses of infrastructure and beach areas across Latin America. This article conducts a comprehensive analysis of case studies in Latin America related to coastal erosion due to hydrodynamic processes. Employing a systematic review approach, data is extracted from Scopus and Web of Science databases. From an initial dataset of 701 records, 62 records meet strict eligibility criteria. Case studies present evidence of how hydrodynamic processes interact with various factors, encompassing oceanic climatic conditions, atmospheric climatic conditions, anthropogenic influences, geomorphological and bathymetric characteristics, geological and tectonic factors, and climate change related aspects. These interactions have an immediate and significant impact on sandy beaches, emphasizing the necessity of comprehensively addressing these linkages when analyzing shoreline changes. This approach aids in identifying key erosion mechanisms and developing effective mitigation measures. Furthermore, the article provides a concise overview of data sources, tools, and methodologies identified in the case studies, spanning from field investigations to the utilization of geographic information systems and numerical models. Underscores the crucial role of international academic collaboration in coastal erosion research, facilitating the adoption of innovative methodologies from other regions, potentially offering a more comprehensive perspective in the formulation of mitigation and adaptation strategies. Finally, potential areas for future research in Latin America are explored, including the assessment of extreme event variability and its impacts on local and regional hydrodynamic processes. This aspect holds critical importance in steering future research towards scenarios that encompass economic and social considerations.

Passive remediation of mine waters from Parys Mountain (Wales): Laboratory column experiments

This study evaluates the effectiveness of dispersed alkaline substrate (DAS) technology to treat highly acidic and contaminated leachates from the oxidation of sulfide-rich mining wastes under wet temperate oceanic climate conditions. To address this issue, leachates from the abandoned mine at Parys Mountain (NW Wales) were passed through two sets of multistep columns filled with a mixture of a fine-grained alkaline reagent (i.e., limestone, MgO, or BaCO3) scattered in an inert matrix. The set of columns with the limestone-DAS plus MgO-DAS combination achieved a near total removal of Fe, Al, Zn, Cu, Mn, As, Co, Cd, and Ni. However, the elimination of SO4 was not significant (around 7%). The limestone-DAS plus BaCO3-DAS combination also achieved a high effectiveness for base metal/loids, allowing the removal of Fe, Al, Zn, Cu, As, and Cd with rates of nearly 100%. In addition, the system with the BaCO3-step had a higher effectiveness in eliminating SO4 (around 53%) than the combined treatment with the MgO-step. According to PHREEQC code calculations, the precipitation of oxy-hydroxy-sulfates (i.e., schwertmannite and basaluminite) and carbonate (i.e., malachite, hydrozincite and calcite) phases may have controlled the solubility of pollutants during the passive treatment. The chemical compositions of the treated waters complied with the threshold values defined by irrigation standards, except for Mn in the BaCO3-DAS output.

Perkinsus olseni in green-lipped mussels Perna canaliculus: diagnostic evaluation, prevalence, and distribution.

Perkinsus olseni (Perkinsidae) is a molluscan parasite notifiable to the World Organisation for Animal Health that is reported in several shellfish hosts in New Zealand, including the native green-lipped mussel Perna canaliculus. Green-lipped mussels comprise over half of New Zealand's aquaculture export value and have historically been considered free of serious diseases based on extensive histology-based surveillance. The discovery of P. olseni in green-lipped mussels has raised questions about future disease threats to green-lipped mussels, particularly under changing ocean climatic conditions. Using mussels collected from farmed (n = 358) and wild (n = 236) populations, we aimed to determine the distribution and prevalence of P. olseni in green-lipped mussels around New Zealand, and assess the performance of diagnostic tests, including real-time PCR, conventional PCR, and culture using Ray's fluid thioglycolate medium (RFTM). Prevalence and diagnostic test performance was evaluated using Bayesian latent class analysis with informative priors. The prevalence of P. olseni was 0-3%, except for 1 wild population from a harbour where prevalence was 22%. Real-time PCR had the highest diagnostic sensitivity (87%) compared to 62 and 21% for conventional PCR and RFTM, respectively. Diagnostic specificity was similar among all methods (96-98%). No mortality was observed during the study. Our results suggest that real-time PCR is the diagnostic test best suited for surveillance of P. olseni in subclinically infected green-lipped mussels under New Zealand conditions.

Variation in Fish Abundance, Diversity and Assemblage Structure in Seagrass Meadows across the Atlanto-Mediterranean Province

Seagrasses worldwide provide key habitats for fish assemblages. Biogeographical disparities in ocean climate conditions and seasonal regimes are well-known drivers of the spatial and temporal variation in seagrass structure, with potential effects on associated fish assemblages. Whether taxonomically disparate fish assemblages support a similar range of ecological functions remains poorly tested in seagrass ecosystems. In this study, we examined variation in the abundance, diversity (from a taxonomic and functional perspective), and assemblage structure of fish community inhabiting nine meadows of the seagrass Cymodocea nodosa across three regions in the Mediterranean (Mallorca and Alicante) and the adjacent Atlantic (Gran Canaria), and identified which attributes typifying the structure of meadows, and large-scale variability in ocean climate, contributed most to explaining such ecological variation. Despite a similar total number of species between Mallorca and Gran Canaria, the latter region had more taxonomically and functionally diverse fish assemblages relative to the western Mediterranean regions, which translated into differences in multivariate assemblage structure. While variation in the abundance of the most conspicuous fish species was largely explained by variation in seagrass structural descriptors, most variation in diversity was accounted for by a descriptor of ocean climate (mean seasonal SST), operating at regional scales. Variation in fish assemblage structure was, to a lesser extent, also explained by local variability in seagrass structure. Beyond climatic drivers, our results suggest that lower temporal variability in the canopy structure of C. nodosa meadows in Gran Canaria provides a more consistent source of food and protection for associated fish assemblages, which likely enhances the more abundant and diverse fish assemblages there.

The influence of calculation error of hourly marine meteorological parameter on building energy consumption calculation

The ocean is a crucial area for future economic development. The marine environment has high energy-efficient and ecological requirements for building construction. Meteorological parameters are the key basis for the analysis and design of building energy efficiency. The lack of meteorological parameters for energy efficiency, particularly hourly data, under oceanic climatic conditions is a universal problem. The appropriate calculation methods of hourly meteorological parameters under oceanic climatic conditions are explored in this study. The impact of the calculation errors of the hourly meteorological parameters on building energy consumption is also analyzed. Three key meteorological parameters are selected: temperature, humidity, and wind speed. Five hourly calculations methods, including linear interpolation, cubic spline interpolation, pieceated three-Hermite interpolation, Akima interpolation, and radial basis function interpolation, are selected to calculate the error of the difference method, with Xiamen, Haikou, and Sanya as the locations of meteorological research. Appropriate interpolation methods are selected for the three parameters, and the seasonal and regional characteristics of the errors of each parameter are compared. Different interpolation methods should be selected for different meteorological parameters in different seasons. The error data of the three parameters of different magnitudes are constructed. A quantitative relationship between the sum of squares due to error of the three meteorological parameters and the rate of change of cooling energy consumption is established. The hourly calculation errors of meteorological parameters have an important impact on the calculation of dynamic energy consumption. The energy consumption differences caused by the errors of different parameters are significant. Obvious regional and seasonal differences also exist. This research strengthens the research foundation of building energy consumption calculation under oceanic climate conditions.

The extreme rainfall gradient of the Cape Horn Biosphere Reserve and its impact on forest bird richness

A natural laboratory is a place supporting the conditions for hypothesis testing under non-anthropogenic settings. Located at the southern end of the Magellanic sub-Antarctic ecoregion in southwestern South America, the Cape Horn Biosphere Reserve (CHBR) has one of the most extreme rainfall gradients in the world. Subject to oceanic climate conditions, it is also characterized by moderate thermal fluctuations throughout the year. This makes it a unique natural laboratory for studying the effects of extreme rainfall variations on forest bird communities. Here, we monitor the bird species richness in the different forest types present in the CHBR. We found that species richness decreased with increasing precipitation, in which an increase of 100 mm in average annual precipitation showed about 1% decrease in species richness. Similar patterns were found among different forest types within the CHBR. These results provide a baseline to investigate the interactions between physical and biotic factors in a subpolar region that climatically contrasts with boreal forests, which is subject to continental climatic conditions. This research highlights the importance of ecological and ornithological long-term studies in the CHBR, which can contribute both to a higher resolution of the heterogeneity of climate changes in different regions of the world, and to orient conservation policies in the Magellanic sub-Antarctic ecoregion in the face of growing development pressures.

Bayesian maximum entropy interpolation of sea surface temperature data: A comparative assessment

ABSTRACT Sea surface temperature (SST) is an important oceanography attribute that has been used to study ocean climatic conditions, ocean dynamics and air-sea interactions. In the present work, the Bayesian maximum entropy (BME) method was used to interpolate a FY-3 C /VIRR satellite dataset in the region with coordinates 120°-150°W and 45°-60°S and during January 2020. A novel approach of constructing valuable soft data was developed by combining BME interpolation with highly correlated SST day and night data differences. The BME interpolation accuracy was assessed by cross-validation, and the results showed that the average RMSE (root mean squared error) was 0.700 and the average bias was 0.441°C. Furthermore, using the Argo data as a basis of comparison, the coverage and accuracy of the BME interpolation of the FY-3 C/VIRR satellite SST dataset were compared numerically with those of the Ordinary Kriging (OK) interpolation of the FY-3 C/VIRR satellite SST dataset and the Optimum Interpolation Sea Surface Temperature (OISST) of the AVHRR satellite SST dataset. It was found that BME had the best SST interpolation performance among the three methods with the lowest average bias and the largest correlation coefficient. Although OISST had a full product coverage rate overall (due to its use of more perfect treatment means), BME’s coverage rate (97.5%) considerably improved that of the FY-3 C/VIRR SST data. Also, both the BME and OK products maintained a 12hrs temporal resolution and a 0.05 decimal degrees longitude/latitude spatial resolution, which is an improvement over OISST data with a 24hrs time resolution and a 0.25 decimal degrees longitude/latitude spatial resolution. Another advantage of BME is that because of its broad theoretical support its performance in practice can be improved further as more knowledge sources become available (which can only be incorporated by BME).

A Driftwood‐Based Record of Arctic Sea Ice During the Last 500 Years From Northern Svalbard Reveals Sea Ice Dynamics in the Arctic Ocean and Arctic Peripheral Seas

AbstractWe present a 500‐year history of naturally felled driftwood incursion to northern Svalbard, directly reflecting regional sea ice conditions and Arctic Ocean circulation. Provenance and age determinations by dendrochronology and wood anatomy provide insights into Arctic Ocean currents and climatic conditions at a fine spatial resolution, as crossdating with reference chronologies from the circum‐Arctic boreal forests enables determination of the watershed the driftwood originated from. Sample crossdating may result in a wide range of matches across the pan‐boreal region, which may be biased toward regions covered by the reference chronologies. Our study considers alternate approaches to selecting probable origin sites, by weighting scores via reference chronology span and visualizing results through spatiotemporal density plots, as opposed to more basic ranking systems. As our samples come from naturally felled trees (not logged or both), the relative proportions of different provenances are used to infer past ocean current dominance. Our record indicates centennial‐to decadal‐scale shifts in source regions for driftwood incursion to Svalbard, aligning with Late Holocene high variability and high frequency shifts in the Transpolar Drift and Beaufort Gyre strengths and associated fluctuating climate conditions. Driftwood occurrence and provenance also track the northward ice formation shift in peripheral Arctic seas in the past century. A distinct decrease in driftwood incursion during the last 30 years matches the observed decline in pan‐Arctic sea ice extent in recent decades. Our new approach successfully employs driftwood as a proxy for Arctic Ocean surface circulation and sea ice dynamics.

English

This work aimed at determining the optimum harvest time of African eggplant (Solanum aethiopicum L.) seeds, cv. Oforiwa and cv. Kpando for maximum physiological seed quality under tropical (TCC) and temperate oceanic climatic (TOC) conditions. Fruit morphological metrics such as fruit weight and size were also related to seed physiological quality. Seeds were harvested at different maturation stages from 20 to 82 days after anthesis (DAA). Seed quality was assessed according to moisture content, dry seed weight, seed length, thousand seed weight, percentage germination and emergence. The results indicated that seeds harvested precociously (20 and 34 days after anthesis), did not germinate or recorded very low percentage germination (0-20%). Considering all the fruit morphological traits and seed quality variables measured, the results indicate that maximum seed quality (that is, germination, emergence, seed weight and mean germination time) are obtained from fruits harvested at 76 DAA. The physiological maturity (PM) (maximum seed dry weight) for cv. Oforiwa was attained at 62 DAA while cv. Kpando took 14 days more to reach physiological maturity but coincided with maximum germination at 76 DAA. The results further showed that fruit characteristics such as weight and size are associated with seed physiological quality in African eggplant. It is thus recommended that fruits of African eggplant cv. Oforiwa and cv. Kpando should be harvested at 70 to 76 DAA for maximum seed germination and emergence. Key words: African eggplant, Solanum aethiopicum, physiological maturity, germination, seed maturation.

Spatio-temporal changes in ocean conditions and primary production in Baffin Bay and the Labrador Sea

Evaluating and understanding bio-environmental relationships at different spatial and temporal scales is important for accurately assessing marine productivity in relation to oceanographic conditions in changing Arctic ecosystems. In this paper, we compare four different bio-environmental datasets, in order to shed new light on the complex marine ecosystem of the Baffin Bay-Labrador Sea region, as well as the historical links between environmental changes and the ecosystem. Satellite dataset was used to describe the regional distribution of chlorophyll a, sea ice concentration (SIC), sea surface temperature (SST) and sea surface salinity (SSS). Chlorophyll a data were also analysed together with shrimp assessment dataset to examine the relationship between marine pelagic productivity and bottom feeders off the Greenland coast. A microfossil dataset (diatom valves) from 57 surface sediment stations was used to describe diatom concentration and diversity across the study region. It was also used in combination with satellite data from the same sites to analyse species-environment relationships and develop a diatom-based transfer function for reconstructing past changes in SIC, SST and SSS. Subsequently, we applied the diatom transfer function on three short sediment cores from off SW and W Greenland spanning the last few centuries. A monitoring dataset of sea ice observations and instrumental measurements of water temperature and salinity, together with atmospheric data (air temperature and wind conditions) from Greenland, were used to develop a more complete picture of 20th and 21st century changes in ocean-climate conditions. Our comparative analyses show clear spatial distribution patterns of marine phytoplankton and identify key ecological groups linked to oceanic conditions. In addition, we find a significant correlation between the different trophic levels, culminating in a ‘productivity boom’ in 2001 CE. On a longer temporal scale, the transfer function reconstructions reveal a good correlation with the satellite, monitoring and observational trends, as well as a consistent, long-term decrease in sea ice linked to ocean-climate variability.

Climate and landscape heterogeneity drive spatial pattern of endemic plant diversity within local hotspots in South-Eastern Alps

Identification of centers of endemism is a crucial issue to improve the understanding on overall biodiversity distribution and related conservation actions. Despite the well-known distribution of global endemic areas, less effort has been devoted in defining local hotspots and their ecological determinants. In this study, we analyzed the distribution and the spatial pattern of endemic diversity of vascular plant in the south-eastern Italian Alps, aiming at identifying the occurrence of local hotspots and focusing on the relationships occurring between alpha (i.e. species richness) and beta diversity (i.e. Local Contributors of Beta Diversity) along with their ecological and spatial drivers. We observed that both alpha and beta diversity metrics have a strong negative relationship, showing a clear spatial pattern. Among the environmental drivers, geomorphological and climatic variables were the most influent, pointing out the importance of landscape heterogeneity and local oceanic climate conditions to favor endemic richness. We also found that historical factors (i.e. Last Glacial Maximum) significantly affected the pattern of endemic diversity. Interestingly, most of the variables showed contrasting effects on alpha and beta diversity.Our study proposes an approach for the identification of local hotspots of endemic species, which take into account both the spatially structured nature of ecological data and their associated environmental drivers. Our findings might provide new insights in the ecological process driving current endemic plant patterns and become pivotal for nature conservationist both to identify areas of high conservation value and to suggest appropriate management schemes also beyond existing protected areas.

Extreme ENSO-driven torrential rainfalls at the southern edge of the Atacama Desert during the Late Holocene and their projection into the 21th century

Abstract Extreme precipitation events and multi-annual droughts, especially in arid to semi-arid subtropical regions, are among the most critical El Nino Southern Oscillation (ENSO) and global climate change impacts. Here, we assess the variability of torrential rainfall during the Late Holocene and its projection into the 21st century at the southern edge of the hyperarid Atacama Desert. The analysis of historical data since the beginning of the 20th century reveals that most (76.5%) alluvial disasters in the southern Atacama Desert (26–30°S) have resulted from extreme rainfall events occurring between March and September under El Nino conditions, and more frequently during the warm phase of the Pacific Decadal Oscillation. Particular rainfall events under these ocean-climate conditions are associated with the convective phase of the Madden-Julian Oscillation (MJO) near the central-equatorial Pacific, resulting in warmer sea surface temperature (SST) there and in the triggering of persistent/intense Pacific South America (PSA) tropical-extratropical teleconnection patterns which result in blocking of the westerly flow at high latitudes and the subsequent deviation of storm tracks towards central-northern Chile. On a longer timescale, marine sediments from Tongoy Bay (30°S) reveal an increasing trend of stronger runoff by torrential coastal rain since ca. 3500 cal yr BP and even stronger heavy rainfall since ca. 1700 cal yr BP. Highly variable coastal sea surface temperatures in the same time span deduced from the sedimentary record can be explained by intensified southerly winds in connection with stronger alongshore pressure gradients and reduced coastal low-cloud cover. Both storm intensification and increased intensity of upwelling-favorable winds point to a variable climate conditioned by strengthened interannual ENSO and interdecadal ENSO-like variability during the Late Holocene. Climate projections from the Coupled Model Intercomparison Project Phase 5 (CMIP5) indicate a reduction in annual precipitation of 15–30% during the current century, together with an intensification of the storms, such as the alluvial disaster on March 25, 2015 in Atacama.

Phenology and time series trends of the dominant seasonal phytoplankton bloom across global scales

AbstractAimThis study examined phytoplankton blooms on a global scale, with the intention of describing patterns of bloom timing and size, the effect of bloom timing on the size of blooms, and time series trends in bloom characteristics.LocationGlobal.MethodsWe used a change‐point statistics algorithm to detect phytoplankton blooms in time series (1998–2015) of chlorophyll concentration data over a global grid. At each study location, the bloom statistics for the dominant bloom, based on the search time period that resulted in the most blooms detected, were used to describe the spatial distribution of bloom characteristics over the globe. Time series of bloom characteristics were also subjected to trend analysis to describe regional and global changes in bloom timing and size.ResultsThe characteristics of the dominant bloom were found to vary with latitude and in localized patterns associated with specific oceanographic features. Bloom timing had the most profound effect on bloom duration, with early blooms tending to last longer than later‐starting blooms. Time series of bloom timing and duration were trended, suggesting that blooms have been starting earlier and lasting longer, respectively, on a global scale. Blooms have also increased in size at high latitudes and decreased in equatorial areas based on multiple size metrics.Main conclusionsPhytoplankton blooms have changed on both regional and global scales, which has ramifications for the function of food webs providing ecosystem services. A tendency for blooms to start earlier and last longer will have an impact on energy flow pathways in ecosystems, differentially favouring the productivity of different species groups. These changes may also affect the sequestration of carbon in ocean ecosystems. A shift to earlier bloom timing is consistent with the expected effect of warming ocean climate conditions observed in recent decades.

Southern Ocean warming and Wilkes Land ice sheet retreat during the mid-Miocene

Observations and model experiments highlight the importance of ocean heat in forcing ice sheet retreat during the present and geological past, but past ocean temperature data are virtually missing in ice sheet proximal locations. Here we document paleoceanographic conditions and the (in)stability of the Wilkes Land subglacial basin (East Antarctica) during the mid-Miocene (~17–13.4 million years ago) by studying sediment cores from offshore Adélie Coast. Inland retreat of the ice sheet, temperate vegetation, and warm oligotrophic waters characterise the mid-Miocene Climatic Optimum (MCO; 17–14.8 Ma). After the MCO, expansion of a marine-based ice sheet occurs, but remains sensitive to melting upon episodic warm water incursions. Our results suggest that the mid-Miocene latitudinal temperature gradient across the Southern Ocean never resembled that of the present day. We demonstrate that a strong coupling of oceanic climate and Antarctic continental conditions existed and that the East Antarctic subglacial basins were highly sensitive to ocean warming.

Operating Energy Savings of a Liquid Desiccant and Evaporative Cooling-Assisted Air-Handling System in Marine Applications

The aim of this study is to analyze the operating energy savings of a liquid desiccant and an indirect and direct evaporative cooling-assisted 100% outdoor air system (LD-IDECOAS) for marine applications. The LD-IDECOAS comprises a liquid desiccant (LD) unit and indirect and direct evaporative coolers (IEC and DEC) to meet the target supply air (SA) conditions. In this study, seawater was used as the cooling source and the waste heat reclaimed from the engine was used as the heating source in the proposed system. The operating energy of the LD-IDECOAS was determined based on detailed energy simulations conducted on two cabins with an area of 16.5 m2, which was compared to a conventional system. The thermal loads on the cabins were estimated using design weather data under various oceanic climate conditions (normal, extremely hot, and extremely cold climates), by adhering to the ISO-7547 standard. The operating energy consumption of the LD-IDECOAS was calculated by modeling the proposed system with a commercial equation solver program (i.e., EES). The results were then compared to those of a conventional constant air volume (CAV) system. The operating energy consumption of the proposed system was reduced by 57–70% in cooling operations and 39% in heating operations under normal climate conditions. In the extremely hot climate regions, the energy consumed by the proposed system was reduced by 56–63% for cooling applications and 39% for heating applications.

On the diversity and richness of understory bryophytes at Nectandra Cloud Forest Reserve, Costa Rica.

BackgroundA survey of the understory bryophytes in the Nectandra Cloud Forest Preserve yielded 1083 specimens distributed among 55 families, represented by 74 genera of mosses, 75 genera of liverworts and 3 of hornworts. We studied and analyzed the bryophytic distribution on six types of substrates: 1) corticolous, 2) epiphyllous, 3) saxicolous, 4) terricolous, 5) aquatic and 6) lignicolous. The richness and composition of bryophyte genera are compared to those of other previous bryophyte surveys from 4 other sites with different oceanic exposures, climatic and geographic conditions in Costa Rica.New informationThis is a report of the first extensive general survey of bryophytes at the Nectandra Reserve, a premontane cloud forest located on the Atlantic slope of Costa Rica, an area much less studied compared to the Monteverde cloud forest on the Pacific slope.

Tree ring-based chronology of hydro-geomorphic processes as a fundament for identification of hydro-meteorological triggers in the Hrubý Jeseník Mountains (Central Europe).

Hydro-geomorphic processes have significantly influenced the recent development of valley floors, river banks and depositional forms in mountain environments, have caused considerable damage to manmade developments and have disrupted forest management. Trees growing along streams are affected by the transported debris mass and provide valuable records of debris flow/flood histories in their tree-ring series. Dendrogeomorphic approaches are currently the most accurate methods for creating a chronology of the debris flow/flood events in forested catchments without any field-monitoring or a stream-gauging station. Comprehensive studies focusing on the detailed chronology of hydro-geomorphic events and analysis of meteorological triggers and weather circulation patterns are still lacking for the studied area. We provide a spatio-temporal reconstruction of hydro-geomorphic events in four catchments of the Hrubý Jeseník Mountains, Czech Republic, with an analysis of their triggering factors using meteorological data from four nearby rain gauges. Increment cores from 794 coniferous trees (Picea abies [L.] Karst.) allowed the identification of 40 hydro-geomorphic events during the period of 1889-2013. Most of the events can be explained by extreme daily rainfalls (≥50mm) occurring in at least one rain gauge. However, in several cases, there was no record of extreme precipitation at rain gauges during the debris flow/flood event year, suggesting extremely localised rainstorms at the mountain summits. We concluded that the localisation, intensity and duration of rainstorms; antecedent moisture conditions; and amount of available sediments all influenced the initiation, spatial distribution and characteristics of hydro-geomorphic events. The most frequent synoptic situations responsible for the extreme rainfalls (1946-2015) were related to the meridional atmospheric circulation pattern. Our results enhance current knowledge of the occurrences and triggers of debris flows/floods in the Central European mountains in transition between temperate oceanic and continental climatic conditions and may prompt further research of these phenomena in the Eastern Sudetes in general.

Late Quaternary developments of Mediterranean oaks in the Atlantic domain of the Iberian Peninsula: The case of the Cantabrian region (N Spain)

Abstract A synthesis of the occurrence of the evergreen oak (Quercus ilex-type) in the Cantabrian region (northern Spain) is presented on the basis of integrated charcoal and pollen analyses. Archaeological charcoal comes largely from sites along the littoral and pre-littoral territories of the Basque Country, Cantabria and Asturias dated from 45 to 3.7 Kyr cal BP, and culturally ranging from Mousterian to Iron Age. Pollen information is produced from a few archaeological sites but mainly from peats and lake sediments. Q. ilex-type is observed as early as at 45-30 Kyr cal BP, with sporadic occurrences in vegetation contexts dominated by Pinus sylvestris-type, which was widely exploited by Mousterian and Aurignacian inhabitants. Afterwards, during the Upper Palaeolithic, there is an important decline, and Q. ilex-type is hardly present between 29 and 15 Kyr cal BP, with open environments dominated by heathland shrubs. From Late Magdalenian onwards, Q. ilex-type expanded again, remaining in the landscape of the Cantabrian region throughout the Holocene, although subordinated in deciduous oak forests under the influence of oceanic climate conditions. Q. ilex-type had a more favourable position than deciduous Quercus across the Cantabrian southern slopes and northwest of the adjacent Iberian Cordillera, where oceanic influences have become attenuated by summer drought and continentality.

Spatial and temporal variability of the frost‐free season in Central Europe and its circulation background

ABSTRACTThe aim of the study was to investigate the temporal and spatial variability of last spring and first autumn frost events as well as the length of the frost‐free season (FFS) in Central Europe in relation to atmospheric circulation. Studies were conducted for the period 1951–2010 using gridded, daily minimum air temperature data obtained from the E‐OBS dataset at 0.25° spatial resolution. To assess the possible impact of air temperature variability on plants, late spring frost events and severe frost events were also examined with respect to the beginning of the thermal growing season. The role of atmospheric circulation was described using Grosswetterlagen circulation types and NAO index, and finally estimated using empirical orthogonal function analysis (EOF). The results confirm a significant increase in the length of the FFS, up to 10 days per decade in the western parts of Europe. This is mostly a result of earlier occurrence of last spring frost in the west up to 5 days. The occurrence of first autumn frost shows no significant trend in most of the studied regions. The obtained spatial pattern of the trends reflects oceanic (west) and continental (east) climatic conditions of the study area. Detailed analysis of circulation types favouring the occurrence of frost in Central Europe indicates that anti‐cyclonic situations are mainly responsible. EOF analyses for the springtime confirm that the first mode, which accounts for 56% of total variance, is related to an extensive high pressure system over eastern Ukraine and Belarus, which brings an inflow of cold, continental air masses to Central Europe. The results provide a broaden information on the region climatologically important due to its transitional location, which may be relevant for investigating past and future trends in spring freeze risk for perennial crops, as changes in the frequency of these airflow patterns will result in changes in the risk of frost damage.