Background Topography Affects the Degree of Three‐Dimensionality of Tidal Sand Waves

Offshore tidal sand waves on the sandy bed of shallow continental shelf seas are more three-dimensional (3D) in some places than others, where 3D refers to a pattern that shows variations in three spatial directions. Such sand waves have crestlines that meander, split or merge. The degree of three-dimensionality seems to vary especially when large-scale bedforms, such as tidal sand banks, are present underneath the sand waves. Understanding this behavior is important for offshore activities, such as offshore windfarm construction or the maintenance of navigation channels. In this study, the degree of three-dimensionality of sand waves at five sites in the North Sea is quantified with a new measure. Results show that tidal sand waves on top of tidal sand banks are more two-dimensional (2D) than those on bank slopes or in open areas. These differences in sand wave pattern are supported by numerical simulations performed with a new long-term sand wave model. The primary cause of these differences is attributed to the deflection of tidal flow over a sand bank, which causes sand wave crests to be more aligned with the bank at its top than at its slopes. It is subsequently made plausible that the different patterns result from the competition between two known mechanisms. These mechanisms are nonlinear interactions between sand waves themselves (SW-SW interactions) and nonlinear interactions between sand banks and sand waves (SB-SW interactions). On bank tops, SB-SW interactions favor a 2D pattern, while SW-SW interactions, which elsewhere produce a 3D pattern, are less effective

Phase-related patterns of tidal sand waves and benthic organisms: field observations and idealised modelling

Observations from the field show that the spatial distribution of benthic organisms is strongly correlated to the morphological structure of tidal sand waves. In particular the troughs of sand waves are typified by a large benthic community, in contrast to the crest. In this paper, we present an idealised process-based model to study these patterns of biota and sand waves. Our model results agree with the observations that these phase-related patterns can arise on the seabed. Moreover, we show that local topography disturbances may lead to spatial patterns of both sand waves and biomass

Review article: Towards a context-driven research:a state-of-the-art review of resilience research on climate change

Since the 1970s, Holling’s socio-ecological systems (SES) approach has been a most predominant theoretical force in resilience research in the context of the climate crisis. From Holling’s approach, however, two contrasting scientific approaches to resilience have developed, namely, naturalism and constructivism. While naturalist resilience research takes SES as complex systems marked by non14 linearity and evolutionary changes, constructivist resilience research focuses on the embeddedness of SES in heterogenous contexts. In naturalist resilience research resilience is defined as a system property, while in constructivist resilience research resilience is politically loaded and historically contingent. The aim of this paper is to review and structure current developments in resilience research in the field of climate change studies, in terms of the approaches, definitions, models and commitments that are typical for naturalism and constructivism; identify the key tension between 20 naturalist and constructivist resilience research in terms of the widely discussed issue of adaptation and transformation, and discuss its implications for sustainable development; and propose a research agenda of topics distilled from the adaptation-transformation tension between naturalist and constructivist resilience research.<br/