Earth Observations for Monitoring Marine Coastal Hazards and Their Drivers

Abstract

Coastal zones have large social, economic and environmental values. They are more densely populated than the hinterland and concentrate large economic assets, critical infrastructures and human activities such as tourism, fisheries, navigation. Furthermore, coastal oceans are home to a wealth of living marine resources and very productive ecosystems. Yet, coastal zones are exposed to various natural and anthropogenic hazards. To reduce the risks associated with marine hazards, sustained coastal zone monitoring programs, forecasting and early warning systems are increasingly needed. Earth observations (EO), and in particular satellite remote sensing, provide invaluable information: satellite-borne sensors allow an effective monitoring of the quasi-global ocean, with synoptic views of large areas, good spatial and temporal resolution, and sustained time-series covering several years to decades. However, satellite observations do not always meet the precision required by users, in particular in dynamic coastal zones, characterized by shorter-scale variability. A variety of sensors are used to directly monitor the coastal zone and their observations can also be integrated into numerical models to provide a full 4D monitoring of the ocean and forecasts. Here, we review how EO, and more particularly satellite observations, can monitor coastal hazards and their drivers. These include coastal flooding, shoreline changes, maritime security, marine pollution, water quality, and marine ecology shifts on the one hand, and several physical characteristics (bathymetry, topography, vertical land motion) of coastal zones, meteorological and oceanic (metocean) variables that can act as forcing factors for coastal hazards on the other hand.

Early Warning from Space for a Few Key Tipping Points in Physical, Biological, and Social-Ecological Systems

“…With regard to the topic of tipping points in marine ecosystems, the future belongs to studies linking these variables to ecological communities and to applications for management, such as the coral reef heat risk alert maps (see Melet et al 2020) and to improved algorithms related to early warning for tipping points, for example, changes in variance and autocorrelation in multiple variables (Carpenter and Brock 2006;Lindegren et al 2012). New types of biological global-scale models based on EO are being implemented to anticipate as early as possible regime shifts in the pelagic ocean.…”

“…Public services with applications to tipping points are being developed. For example, EO SST data are incorporated into algorithms that provide near-real-time global maps of coral bleaching thermal stress risk (http://coral reefw atch.noaa.gov) (see also Melet et al 2020). These are just a few examples.…”

“…These phenomena do not occur in all systems, and multidecadal time series are necessary to correctly assess the natural variability of the system and its changes near a tipping point. Despite these limitations, early warning is a very promising field, which can become a major element of disaster risk reduction (Melet et al 2020) and deserves more research to become entirely applicable.…”

Marine terraces of the last interglacial period along the Pacific coast of South America (1° N–40° S)

“…Tectonically active coasts are highly dynamic geomorphic environments and they host densely-populated centers and associated infrastructure (Melet et al, 2020). Coastal areas have been episodically affected by the effects of sea-level changes at glacial timescales, drastically modifying the landscape and leaving behind fossil geomorphic markers, such as former paleo-shorelines, abrasion platforms, and marine terraces (Lajoie, 1986).…”

Guest Editorial: International Space Science Institute (ISSI) Workshop on Geohazards and Risks Studied from Earth Observations

“…Due to their social, economic and environmental values to human society, coastal zones experience high stresses and suffer from higher vulnerability to different natural and anthropogenic hazards such as storm surges, marine heat waves, coastal flooding, sea level rise, erosion and shoreline retreat, acidification and destruction of ecosystems. In that context, Melet et al (2020) investigate what are the benefits of EOs to monitor coastal hazards and their drivers via the development of monitoring programs and early warning forecasting systems. One of the most massive natural hazards that also causes tremendous destruction in coastal areas is tsunamis.…”