Search results for "hydrography"

Growth-increment characteristics and isotopic (delta O-18) temperature record of sub- thermocline Aequipecten opercularis (Mollusca: Bivalvia): evide…

2021

Abstract The shell δ18O of young modern Aequipecten opercularis from the southern North Sea provides an essentially faithful record of seasonal variation in seafloor temperature. In this well-mixed setting, A. opercularis shell δ18O also serves as a proxy for seasonal variation in surface temperature. Individuals from less agitated (e.g. deeper) settings in a warm climate would not be expected to record the full seasonal range in surface temperature because of thermal stratification in summer. Such circumstances have been invoked to explain cool isotopic summer temperatures from early Pliocene A. opercularis of eastern England. Support for a sub-thermocline setting derives from high-amplitu…

Ocean Circulation Model Applications for the Estuary-Coastal-Open Sea Continuum

2021

Coastal zones are among the most variable environments. As such, they require adaptive water management to ensure the balance of economic and social interests with environmental concerns. High quality marine data of hydrographic conditions e.g., sea level, temperature, salinity, and currents are needed to provide a sound foundation for the decision making process. Operational models with sufficiently high forecasting quality and resolution can be used for a further extension of the marine service toward the coastal-estuary areas. The Limfjord is a large and shallow water body in Northern Jutland, connecting the North Sea in the West and the Kattegat in the East. It is currently not covered …

8.2 ka event North Sea hydrography determined by bivalve shell stable isotope geochemistry.

2019

AbstractThe abrupt 8.2 ka cold event has been widely described from Greenland and North Atlantic records. However, its expression in shelf seas is poorly documented, and the temporal resolution of most marine records is inadequate to precisely determine the chronology of major events. A robust hydrographical reconstruction can provide an insight on climatic reaction times to perturbations to the Atlantic Meridional Overturning Circulation. Here we present an annually-resolved temperature and water column stratification reconstruction based on stable isotope geochemistry of Arctica islandica shells from the Fladen Ground (northern North Sea) temporally coherent with Greenland ice core record…

Artificial Reefs in North-West Sicily: Comparisons and Conclusions

2000

The most notable features of the biotic colonization and fishing yield of artificial reefs are a straightforward response to local environmental conditions. When applying this assumption to the artificial reefs of north-west Sicily, the features that distinguish the reefs from each other are largely consistent with the major hydrographic characteristics of the Gulf of Castellammare, the Bay of Carini and the Gulf of Palermo. The differences in environmental conditions in the three biotopes have made it possible to compare the colonization of artificial reefs in unpolluted oligotrophic water (Bay of Carini), eutrophic water (Gulf of Palermo) and water with heavy siltation rates (Alcamo Marin…

The impact of the Little ice age on coccolithophores in the central Mediterranea Sea

2010

The Little Ice Age (LIA) is the last episode of a series of Holocene climatic anomalies. There is still little knowledge on the response of the marine environment to the pronounced cooling of the LIA and to the transition towards the 20th century global warming. Here we present decadal-scale coccolithophore data from four short cores recovered from the central Mediterranean Sea (northern Sicily Channel and Tyrrhenian Sea), which on the basis of <sup>210</sup>Pb activity span the last 200–350 years. The lowermost part of the record of one of the cores from the Sicily Channel, Station 407, which extends down to 1650 AD, is characterized by drastic changes in productivity. Specific…

Short-duration rainfalls in Sicily

1990

The Italian Hydrographic Service publishes yearly maximum rainfall depths with 1-, 3-, 6-, 12-, and 24-hr duration, recorded by recording rain gauges. It also publishes selected short-duration (t<1 hr) rainfall amounts. It is impossible to carry out a statistical analysis of the short-duration rainfalls for each recording rain gauge because the published data correspond to different record durations and to different recording rain gauges from year to year. Therefore, there is a practical need to derive empirical relationships between the 1-, 3-, 6-, 12-, and 24-hr duration amounts and shorter duration (t<1 hr) rainfall amounts. Such a relationship has been proposed by Bell and has been veri…

Are calanco landforms similar to river basins?

2017

In the past badlands have been often considered as ideal field laboratories for studying landscape evolution because of their geometrical similarity to larger fluvial systems. For a given hydrological process, no scientific proof exists that badlands can be considered a model of river basin prototypes. In this paper the measurements carried out on 45 Sicilian calanchi, a type of badlands that appears as a small-scale hydrographic unit, are used to establish their morphological similarity with river systems whose data are available in the literature. At first the geomorphological similarity is studied by identifying the dimensionless groups, which can assume the same value or a scaled one in…

2021

Bulk stable nitrogen isotope values of the carbonate-bound organic matrix in bivalve shells (δ15NCBOM) are increasingly used to assess past food web dynamics, track anthropogenic nitrogen pollution and reconstruct hydrographic changes. However, it remains unresolved if the δ15NCBOM values are also affected by directed ontogenetic trends which can bias ecological and environmental interpretations. This very aspect is tested here with modern and fossil specimens of the long-lived ocean quahog, Arctica islandica, collected from different sites and water depths in the NE Atlantic Ocean. As demonstrated, δ15NCBOM values from the long chronologies show a general decrease through lifetime by −0.00…

Changes in Latvian river discharge regime at the turn of the century

2012

The study deals with turn-of-the-century changes in the total annual river runoff distribution and high and low flows in Latvia, covering river basins within four hydrological districts which vary according to size and physiographical conditions. Mathematical statistical methods were applied in the analysis of river discharge data series for two study periods of 1951–2009 and 1881–2009. The present results confirm the basic statement concerning the Baltic countries that major significant changes in river runoff during the last two decades have occurred between spring (decrease) and winter (increase) seasons. Mostly insignificant changes in summer runoff and significant/insignificant changes…

From Slope Morphometry to Morphogenetic Processes: An Integrated Approach of Field Survey, Geographic Information System Morphometric Analysis and St…

2015

Calanchi (singular: calanco) represent a typical example of badlands in the Italian peninsula, which rapidly evolve on clayey terrains such as the widespread Pliocene–Pleistocene marine clays. The present study aimed at investigating the role of the slope morphometry on the typology and distribution of morphogenetic processes in a calanchi area located in southern Italy. The research included detailed geomorphological surveying as well as morphometric and statistical analyses. The study area was first subdivided into individual hydrographic units (HUs), for which field survey allowed to identify the dominant denudation processes, their intensity and the distribution of the associated landfo…