ALBERT

Beschreibung: Journal of Hydrometeorology, Volume 20, Issue 3, Page 397-410, March 2019. 〈br/〉

Beschreibung: Sea surface temperature (SST) anomalies in the tropical Atlantic have been associated with precipitation anomalies in West Africa that form a dipole pattern with centers over the Sahel and the Gulf of Guinea. Whilst this was clear before the 1970's, the dipole pattern almost disappeared after that date, as the anti-correlation between rainfall anomalies in the Sahel and Guinea dropped abruptly. Simultaneously, the anti-correlations between Sahel rainfall and tropical Pacific SSTs strengthened. It has been posited that these changes after the 1970's developed as rainfall over West Africa started to co-vary with SSTs in the global tropics. In this co-variability, enhanced summer rainfall over West Africa with a monopole pattern corresponds to warmer SSTs in the tropical Atlantic and Maritime Continent, and colder SSTs in the tropical Pacific and western Indian Oceans. The present paper describes the hitherto unexplored seasonal evolution of this co-variability and the physical mechanisms at work. Sensitivity experiments with two atmospheric general circulation models demonstrate that, after the 1970's, the impacts of SST anomalies in the Indo-Pacific counteract those in the Atlantic in terms of generating rainfall anomalies over the Sahel, and that this superposition of effects is primarily linear. Therefore, at interannual timescales, the change in the patterns of co-variability between West African rainfall and tropical SSTs can explain the non-stationary relationship between the anomalies in these two fields.

Beschreibung: Abstract Ni is an essential cofactor in NiFe‐uptake hydrogenase, an enzyme regulating H2 metabolism in diazotrophic cyanobacteria, the major H2 producers in the surface ocean globally. Here, we investigated the effect of Ni supply on H2 production and N2 fixation by using a model marine cyanobacterial diazotroph, Cyanothece. By mediating total dissolved Ni concentrations from 100 to 0.03 nmol L−1 in a trace metal‐defined culture medium, we demonstrated that Ni deficiency results in H2 accumulation, coupled with decreasing Ni quotas, growth rates, and occasionally relatively low N2 fixation rates. These results indicate that Ni deficiency limits the growth of the Cyanothece to some extent, considerably decreases H2 uptake by hydrogenase and leads to H2 accumulation and N2 fixation variation in the diazotroph. The findings show that Ni availability is a critical factor on controlling H2 production and N2 fixation in marine diazotrophic cyanobacteria. The information of Ni bioavailability for diazotrophic cyanobacteria is thus essential to evaluate the importance of Ni for H2 cycling and N2 fixation in oceanic surface waters.

Beschreibung: ABSTRACT [1]  We present a numerical model that shows the transgressing upper shoreline of wave-dominated estuaries (bayhead deltas), which commonly contain populous urban and industrial centers, stabilize and their rate of retreat decreases at tributary junctions. The decreased rate of retreat across a tributary junction is caused by a decrease in total accommodation while sediment supply remains conserved. Our model predicts that bayhead deltas from smaller systems will be located closer to tributary confluences than their larger counterparts. An examination of modern bayhead deltas in Albemarle Sound, US Atlantic Coast reveals that bayhead deltas from smaller tributaries are located closer to tributary confluences than bayhead deltas associated with larger tributaries, supporting our model prediction. Our results highlight the importance of antecedent topography created during falling sea levels on shaping the nature of transgression during the ensuing sea-level rise. In particular, tributary junctions act as pinning points during transgression.

Beschreibung: Sea-level anomalies are intra-seasonal increases in water level forced by meteorological and oceanographic processes unrelated to storms. The effects of sea-level anomalies on beach morphology are unknown, but important to constrain because these events have been recognized over large stretches of continental margins. Here, we present beach erosion measurements along Onslow Beach, a barrier island on the U.S. East Coast, in response to a year with frequent sea-level anomalies and no major storms. The anomalies enabled extensive erosion, which was similar and in most places greater than the erosion that occurred during a year with a hurricane. These results highlight the importance of sea-level anomalies in facilitating coastal erosion and advocate for their inclusion in beach-erosion models and management plans. Sea-level anomalies amplify the erosive effects of accelerated sea-level rise and changes in storminess associated with global climate change.

Beschreibung: Marine megafauna, including seabirds, are critically affected by fisheries bycatch. However, bycatch risk may differ on temporal and spatial scales due to the uneven distribution and effort of fleets operating different fishing gear, and to focal species distribution and foraging behaviour. Scopoli's shearwater Calonectris diomedea is a long-lived seabird that experiences high bycatch rates in longline fisheries and strong population-level impacts due to this type of anthropogenic mortality. Analyzing a long-term data set on individual monitoring, we compared adult survival (by means of multi-event capture-recapture models) among three close predator-free Mediterranean colonies of the species. Unexpectedly for a long-lived organism, adult survival varied among colonies. We explored potential causes of this differential survival, by: (1) measuring egg volume as a proxy of food availability and parental condition; (2) building a specific longline bycatch risk map for the species; and (3) assessing the distribution patterns of breeding birds from the three study colonies via GPS tracking. Egg volume was very similar between colonies over time, suggesting that environmental variability related to habitat foraging suitability was not the main cause of differential survival. On the other hand, differences in foraging movements among individuals from the three colonies expose them to differential mortality risk, which likely influenced the observed differences in adult survival. The overlap of information obtained by the generation of specific bycatch risk maps, the quantification of population demographic parameters and the foraging spatial analysis should inform managers about differential sensitivity to the anthropogenic impact at mesoscale level and guide decisions depending on the spatial configuration of local populations. The approach would apply and should be considered in any species where foraging distribution is colony-specific and mortality risk varies spatially. This article is protected by copyright. All rights reserved.

Beschreibung: Ecosystems at the land–sea interface are vulnerable to rising sea level. Intertidal habitats must maintain their surface elevations with respect to sea level to persist via vertical growth or landward retreat, but projected rates of sea-level rise may exceed the accretion rates of many biogenic habitats. While considerable attention is focused on climate change over centennial timescales, relative sea level also fluctuates dramatically (10–30 cm) over month-to-year timescales due to interacting oceanic and atmospheric processes. To assess the response of oyster-reef ( Crassostrea virginica ) growth to interannual variations in mean sea level (MSL) and improve long-term forecasts of reef response to rising seas, we monitored the morphology of constructed and natural intertidal reefs over 5 years using terrestrial lidar. Timing of reef scans created distinct periods of high and low relative water level for decade-old reefs ( n  = 3) constructed in 1997 and 2000, young reefs ( n  = 11) constructed in 2011 and one natural reef (approximately 100 years old). Changes in surface elevation were related to MSL trends. Decade-old reefs achieved 2 cm/year growth, which occurred along higher elevations when MSL increased. Young reefs experienced peak growth (6.7 cm/year) at a lower elevation that coincided with a drop in MSL. The natural reef exhibited considerable loss during the low MSL of the first time step but grew substantially during higher MSL through the second time step, with growth peaking (4.3 cm/year) at MSL, reoccupying the elevations previously lost. Oyster reefs appear to be in dynamic equilibrium with short-term (month-to-year) fluctuations in sea level, evidencing notable resilience to future changes to sea level that surpasses other coastal biogenic habitat types. These growth patterns support the presence of a previously defined optimal growth zone that shifts correspondingly with changes in MSL, which can help guide oyster-reef conservation and restoration. To assess the response of oyster-reef ( Crassostrea virginica ) growth to interannual variations in mean sea level (MSL) and improve long-term forecasts of reef response to rising seas, we monitored the morphology of constructed and natural intertidal reefs over 5 years using terrestrial lidar. Timing of reef scans created distinct periods of high and low relative water level for each generation of reefs, and changes in surface elevation followed trends in MSL during the two sampling periods. Oyster reefs appear to be in dynamic equilibrium with short-term (month-to-year) fluctuations in sea level, evidencing notable resilience to future changes to sea level that surpasses other coastal biogenic habitats.

Beschreibung: ABSTRACT It is well known how mountains play a crucial role in the climate system and have very particular climate features compared to other regions. Sierra de Guadarrama is a part of the Iberian Peninsula Central System (Spain), a mountain range located in the center of an extensive plateau, dominated by a continental Mediterranean climate but under a strong Atlantic influence. This range provides fresh water to the different settlements in its vicinity, providing enough water resources to several millions of inhabitants, crop fields, industries and the city of Madrid, the capital of Spain. Nevertheless, there is no work studying the role of the synoptic scale in relation to the precipitation in this mountain range. To tackle this problem, this work calculates water vapour flux patterns (WVFPs) using total column water vapour flux as a predictor field due to the close relation between this parameter and the precipitation in mountainous areas. A clustering analysis on the first three principal components of the predictor field was performed and seven differentiated WVFPs were found using a cost function considering local precipitation data for optimum number of cluster determination. Then, an analysis is made for each component in terms of synoptic relation with other fields and well-known broader teleconnection patterns. Finally, an analysis in terms of their contribution to total precipitation, mean rain intensity and probability of precipitation is made. This work is expected to bring new light on the knowledge of precipitation climatology over this crucial and still not very well-known area, and it is a solid step for future precipitation modelling tools validation that combined with reliable measurements will allow to produce realistic precipitation assessments and forecasts in order to improve the hydrological management of this complex area.

Beschreibung: The purpose of our study was to evaluate the protective effect of melatonin in a rat model of caerulein-induced acute pancreatitis. For the induction of experimental acute pancreatitis, four subcutaneous injections of caerulein (20 µg kg –1 body weight) were given to Wistar rats at 2-h intervals. Melatonin was injected intraperitoneally (25 mg kg –1 body weight) 30 min before each caerulein injection. After 12 h, rats were sacrificed by decapitation. Blood and pancreas samples were collected and processed for serological and histopathological studies, respectively. Lipase, α-amylase, corticosterone, total antioxidant power and cytokines interleukin (IL)-1β, IL-4 and tumour necrosis factor (TNF)-α were determined using commercial kits. ANOVA and Tukey tests ( P  〈 0.05) were performed for the statistical analysis of the results. Results showed that the administration of melatonin reduced histological damage induced by caerulein treatment as well as the hyperamylasemia and hyperlipidemia. Corticosterone and antioxidant total power were also reverted to basal activities. Furthermore, melatonin pre-treatment reduced pro-inflammatory cytokines IL-1β and TNF-α and increased the serum levels of anti-inflammatory cytokine IL-4. In conclusion, the findings suggest that the protective effect of melatonin in caerulein-induced acute pancreatitis is mediated by the anti-inflammatory ability of this indolamine. Thus, melatonin may have a protective effect against acute pancreatitis. Copyright © 2013 John Wiley & Sons, Ltd.

Beschreibung: ABSTRACT Proxies, such as changes in beach profiles and shoreline positions, are commonly used in management and research for estimating changes in subaerial beach volume; however, the accuracy of these proxies across increasing time scales and complex morphologies is unclear. Volume changes associated with along-beach morphologic variability may not be captured well by changes in profiles, while volume changes associated with across-beach morphologic variability may not be captured well by measuring shoreline change. This study assesses the impacts of morphologic variations, associated with beach cusps and nourishment material, on volume change estimates from profiles and shoreline change at 0.5 to 3.5 year time periods. Results indicate that profiles spaced ≥ 150 m apart and the shoreline-change proxy will likely estimate volume change inaccurately over periods ≤ 1 year at beaches that are consistently eroding or accreting and contain cusps. However, over longer time periods (1-3.5 years), estimates of volume change from both proxies improved at those types of beaches. Volume changes at the edges of nourishment areas are not captured well by profiles. When the nourishment material is graded to a ramped morphology, which minimizes across-beach morphologic variability, the shoreline-change proxy does accurately estimate volume changes. Both proxies estimate volume changes inaccurately at beaches where volume changes oscillate between erosion and accretion on both short and long time scales because the magnitude of small-scale changes in volume from the formation and erosion of morphologic features, such as cusps and berms, will always be similar to the longer-term net volume change. This study suggests that decadal records of shoreline change, which are commonly developed using aerial photography, can be used to help identify the best proxy for estimating volume change; however, recent anthropogenic modifications that impact patterns of beach sedimentation, including nourishment, terminal groins, and inlet-channel dredging, makes decadal records less useful. This article is protected by copyright. All rights reserved.