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Coastal floods, driven by extreme sea levels, are one of the most dangerous natural hazards. The people at highest risk are those living in low-lying coastal areas exposed to tropical-cyclone-forced storm surges. Here we apply a novel modelling framework to estimate past and/or present and future storm-surge-level and extreme-sea-level probabilities along the coastlines of southern China, Vietnam, Cambodia, Thailand, and Malaysia. A regional hydrodynamic model is configured to simulate 10 000 years of synthetic tropical cyclone activity, representative of a past/present (1980–2017) and high-emission-scenario future (2015–2050) period. Results show that extreme storm surges, and therefore total water levels, will increase substantially in the coming decades, driven by an increase in the frequency of intense tropical cyclones. Storm surges along the southern Chinese and northern and southern Vietnamese coastlines increase by up to 1 m, significantly larger than expected changes in mean sea-level rise over the same period. The length of coastline that is presently exposed to storm surge levels of 2.5 m or greater will more than double by 2050. Sections of Cambodian, Thai, and Malaysian coastlines are projected to experience storm surges (at higher return periods) in the future, not previously seen, due to a southward shift in tropical cyclone tracks. Given these findings, coastal flood management and adaptation in these areas should be reviewed for their resilience against future extreme sea levels.

Ocean Currents: Physical Drivers in a Changing World opens with a general introduction to the character, measurement, and simulation of ocean currents, leading to a physical and dynamical framework for understanding the wide variety of flows encountered in the oceans. The book comprises chapters covering distinct aspects of contrasting ocean currents: broad and slow, deep and shallow, narrow and swift, large scale and small scale, low latitudes and high latitudes, and moving in horizontal and vertical planes. Through this approach the authors cover a wide range of applications, from local to global, with considerable geographical context. Provides analyses of ocean observations and numerical model simulations, highlighting the pathways and drift associated with ocean currents, around the World Ocean, linked to online exercises for instructors and students that extend this perspective Presents applications to natural phenomena, showing how ocean currents shape marine ecosystems, helping researchers understand the distribution and adaptation of life in the oceans Addresses societal challenges, specifically how ocean currents disperse pollutants (e.g. plastic) from coastal sources and how the global ocean circulation is central to our changing climate, helping students and researchers develop an interdisciplinary approach to global environmental change

Oceanic influences on shelf seas are mediated by flow along and across continental slopes, with consequences for regional hydrography and ecosystems. Here we present evidence for the variable North Atlantic influence on European shelf seas over the last 4 decades using ocean analysis and reanalysis products, as well as an eddy-resolving ocean model hindcast. To first order, flows oriented along isobaths at the continental slope are related to the poleward increase in density in the adjacent deep ocean that supports a geostrophic inflow towards the slope. In the North Atlantic, this density gradient and associated inflow have undergone substantial, sometimes abrupt, changes in recent decades. Inflow in the range 10–15 Sv is identified with eastward transport in temperature classes at 30∘ W in the latitude range 45–60∘ N. Associated with major subpolar warming around 1997, a cool and fresh branch of the Atlantic inflow was substantially reduced, while a warm and more saline inflow branch strengthened, with respective changes of the order of 5 Sv. Total inflow fell from ∼ 15 Sv pre-1997 to ∼ 10 Sv post-1997. In the model hindcast, particle tracking is used to trace the origins of poleward flows along the continental slope to the west of Ireland and Scotland before and after 1997. Backtracking particles up to 4 years, a range of subtropical and subpolar pathways is identified from a statistical perspective. In broad terms, cold, fresh waters of subpolar provenance were replaced by warm, saline waters of subtropical provenance. These changes have major implications for the downstream shelf regions that are strongly influenced by Atlantic inflow, in particular the northern North Sea, where “subtropicalization” of ecosystems has already been observed since the late 1990s.

Hurricane activity has been higher since 1995 than in the 1970s and 1980s. This rise in activity has been linked to a warming Atlantic. In this study, we consider variability of the volume of water warmer than 26.5 ºC, considered widely to be the temperature threshold crucial to hurricane development. We find the depth of the 26.5 ºC isotherm better correlated with seasonal hurricane counts than SST in the early part of the Atlantic hurricane season in some regions. The volume of water transformed by surface heat fluxes to temperatures above 26.5 ºC is directly calculated using the Water Mass Transformation framework. This volume is compared with the year-to-year changes in the volume of water of this temperature to see how much of the volume can be explained using this calculation. In some years, there is notable correspondence between transformed and observed volume anomalies, but anomalies in other years must be largely associated with other processes, such as the divergence of horizontal heat transport associated with the AMOC. This technique provides evidence that, in a given year, coordinated physical mechanisms are responsible for the build-up of anomalous ocean heat; not only net surface heat exchange but also the convergence of horizontal heat transport from ocean currents, to provide fuel for larger numbers of intense hurricanes.

The last decades witnessed an increase in Arctic offshore operations, partly driven by rising energy needs and partly due to easing of sea ice conditions and improved accessibility of shipping routes. The study examines changes in sea ice and ocean conditions in the Arctic with their implications for off-shore safety. The objective of the research is to develop a basis for forecasting technologies for maritime operations. We assess loads on off-shore structures from sea ice and ocean in centennial climate future projections and implications for the accessibility and future Arctic shipping. As a test case, we calculate loads on a tubular structure of 100-m wide and 20-m tall, similar to installations in the Beaufort Sea in the 1980s. With sea ice retreating, loads are predicted to increase from ~0.1 × 106 N (MN) at present to ~50–200 MN in the 2090s, primarily due to wave loads. This study asserts the need for new approaches in forecasting to make marine operations in the Arctic safer.

Observational rain gauge/satellite and reanalysis datasets since the 1950s are evaluated for trends in mean and extreme rainfall in and around Mainland Southeast Asia (MSEA). Rain gauge data indicate strong increases exceeding 50% in both annual mean precipitation and various extreme precipitation indices over Vietnam and the northwestern part of the peninsula since 1979. The remote influence of ENSO may partially explain the recent precipitation trend toward a more intense regional hydrological cycle, in response to predominant La Niña states over recent decades. Increasing precipitation in MSEA is also associated with increased monsoon intensity in southeast Asia and a northward shift of the monsoon activity center toward MSEA over 1979–2018. Warming-driven evaporation increases were obtained over the adjacent seas typically feeding precipitation over MSEA associated with a shift toward predominantly positive phases of the two major natural climate variability modes of the tropical Indian Ocean, namely the Indian Ocean Dipole and the Indian Ocean Basin Mode. A moisture budget analysis using ERA5 re-analysis data showed increasing oceanic moisture transports along the typical winter and summer moisture pathways toward the MSEA. However, results show that during summer the major part of increased moisture from the oceanic moisture sources ends up as precipitation over the oceanic regions adjacent to MSEA with ERA5 not being able to produce the observed positive trends in summer continental precipitation. On the other hand, ERA5 reveals pronounced increases in winter precipitation over the MSEA, in accordance with rain-gauge data, associated with strongly increasing transport of moisture originated from the western tropical Pacific and the South China Sea.