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Recent observations have heightened concerns that the reduced density of coastal water is leading to a decrease in the frequency of basin water renewal in Norwegian sill fjords. There are indications that coastal water is becoming lighter due to climate change. The renewal of fjord basin water constitutes the primary source of oxygenation in these fjords, and many sill fjords naturally undergo stagnation periods lasting up to several years. In this paper, we have mapped alterations in coastal water using time series data from hydrographic measurements along the coastline, utilizing them as input for a simplified two-layer fjord model. We demonstrate that the temperature has risen, salinity has decreased, and consequently, the density of coastal water has declined since approximately 1990. At a depth of 10 m, the rise in temperature and the reduction in salinity made similar contributions to the decrease in density. However, at depths of 50 and 100 m, the increasing temperature emerged as the primary factor. The density exhibited a more substantial decrease in the upper layers compared to the lower layers. Consequently, not only was the water less dense, but the stability of the water column had also increased. The estimated temperature in the fjord basins increased after 1990 in 98 out of 101 evaluated fjords, with an average increase of 0.6 °C. The altered coastal stratification had an impact on the estimated work against the buoyant forces in the fjord basins. In 78 out of the 101 fjords, the work against buoyant forces by diapycnal mixing increased. In most of the fjord basins where the work against buoyant forces increased, the rise was insufficient to compensate for the decreasing density at the coast. Consequently, basin water renewal occurred less frequently in 65 out of the 101 fjord basins along the Norwegian coast. • Coastal monitoring in Norway show altered coastal climate since 1930. • The Norwegian coastal water has decreased in density. • The stratification along the Norwegian coast is intensified. • Both coastal water and fjord basin got warmer after 1990. • Water exchange in fjord basins occure less frequent than before. [ABSTRACT FROM AUTHOR]

From the 2013 ECSA conference ‘Estuaries and Coastal Areas in Times of Intense Change’ a theme emerged that has ended up being the focus of this Special Issue of Estuarine Coastal and Shelf Science, namely ‘Changes to processes in estuaries and coastal waters due to intense multiple pressures’. Many parts of the world are continuing to experience unprecedented rates of economic growth, and those responsible for managing coastal and estuarine areas must respond accordingly. At the same time, global climate change and sea level rise are also continuing, placing new or more intense pressures on coastal areas that must be dealt with in ways that are as far as possible managed as a result of good scientific understanding. There are other pressures too, which depend on the system concerned. This article provides an overview of the papers contained within the Special Issue and provides a discussion of how these fit within the main theme of intense multiple stressors, considering how a balance can be achieved between the needs of various different stakeholders and interest groups, and the sustainability of the system concerned. We categorise the papers in four main groupings: (1) stressors related to sea level rise; (2) stressors related to changes in fresh water inputs; (3) stressors related to anthropogenic pollution; and (4) the use of indicators as a means of assessing the effects of stressors, and reflect on the fact that despite the diversity of different challenges and geographical regions involved many of the approaches and discussions contained within the Special Issue have strong similarities, leading to a set of overarching principles that should be considered when making recommendations on management strategies. [ABSTRACT FROM AUTHOR]