Marine heatwaves

Clearly communicating baselines for assessing ocean warming is essential for understanding extreme events and how they will affect marine ecosystems and livelihoods in the future.

High-temperature, high-acidity and low-oxygen extremes may pose a particular threat to marine ecosystems, requiring a major effort to understand them and the ability of marine life to respond to them.

Marine heatwave assessments based on three different sea-surface-temperature products show significant spread in occurrence, duration and long-term trend in both coastal and open ocean settings in Asia and the Indo-Pacific, possibly due to differences in sensors, procedures, and sea ice treatments.

Marine heatwaves in the shallow coastal zone of the Baltic Sea have become more frequent and longer, leading to a reduction in oxygen concentration at levels considered dangerous to marine ecosystems, according to evaluations of in situ data and different reanalysis products.

Marine heat waves in the Brazil Malvinas Confluence region are associated with high eddy kinetic energy, primarily linked to mesoscale flows, whereas marine cool spells are associated with low eddy kinetic energy and both mesoscale and mean current regimes, according to an analysis of observation-based data.

Sea ice retreat in the shallow marginal seas of the Arctic Ocean during the mid-summer maximum of downward radiative flux has led to unprecedented marine heatwaves that have become much more likely as a result of global warming, according to analyses of observations and model simulations.

Future climate change can trigger air-sea feedbacks in the Northeast Pacific, further raising the intensity and spatial extent of summer marine heatwaves beyond the long-term warming, according to model simulations using a novel storyline approach.

Tropical cyclones that interact with marine heatwaves increase their intensity by 35.4% in the western North Pacific and North Atlantic basin as a result of increased latent heat flux and higher precipitation, according to an analysis of tropical cyclone data between 1982 and 2019.

Frontal activity and chlorophyll concentrations have increased in high latitude hotspots of ocean warming but have decreased in equatorial and subtropical gyre hotspots, suggest changes in satellite remotely sensed sea surface temperature and chlorophyl concentration between 2003 and 2020.

Cold rings associated with the Eastern Australian Current can push warm water onto the shelf off Sydney, leading to persistent coastal marine heatwaves, according to analyses of satellite data, in situ observations and reanalyses.

The authors identify four main types of vertical structures of marine heatwaves, with different impact depths and spatio-temporal distributions, that are influenced by multiscale ocean dynamical processes.

This study examines the effect of four marine heatwaves in the Northeast Pacific on the distributions of 14 top predators, revealing a wide-array of predator responses both among and within heatwaves. Predator responses were highly predictable, demonstrating capacity for early warning systems of heatwave impacts, similar to weather forecasts.

Coastal marine heatwaves off Eastern Australia that extend throughout the water column are linked to intrusion of the Eastern Australian Current, whereas those with no surface signature are related to downwelling favourable winds, according to a 28-year in-situ record of daily ocean temperatures.

Frequency, intensity and duration of subsurface marine heatwaves can be predicted at seasonal timescales and with greater skill than surface events, suggest analyses with an operational seasonal prediction system.

Marine heatwave events in the Northeast Pacific were more intense, lasted longer and occurred more frequently during positive phases of the Pacific Decadal Oscillation over the past 40 years, according to analyses of observations and climate model simulations.

New paper by Bian and colleagues shows that oceanic mesoscale eddies act as a dominant driver of #marine #heatwave life cycles over most parts of the global #ocean.

The authors investigate marine heatwaves on the ocean bottom in the shallow waters surrounding North America. Relative to their surface counterparts, bottom marine heatwaves are often more intense, more persistent, and can occur independently.

The increase in marine heat wave days in the Northeast Pacific ocean over the past few decades is linked to Arctic warming and sea ice decline, according to analyses of satellite-derived and reanalysis data along with idealized coupled climate model experiments.

Here, the authors use an advanced data-mining method to show how “extreme modes” of large-scale climate variability, such as El Niño, can lead to devastating marine heatwaves.

Increases in high-impact marine heatwaves over the past few decades are found to be due to recent acceleration in long-term ocean surface warming, stressing the need of careful attribution of climate change impact on extreme events.

Increased extreme high sea level events and concurrence of marine heatwaves are observed along the Indian Ocean coast of Indonesia in the past decade due to the combined impact of anthropogenic warming and natural decadal climate variability.

Small-scale fishers exhibit more active adaptive and transformative responses in areas with higher exposure levels to climate change hazards, according to a global systematic review approach of social-ecological systems.

Long term coastal surface and sub-surface monitoring reveals that warm temperature extremes have intensified and cold extremes nearly vanished in the last decades, increasing baseline water temperature on the southwest coast of Finland.

Compound extreme events in two or more oceanic ecosystem stressors are increasingly considered as a major concern for marine life. Here the authors present a first global analysis on compound marine heatwave and ocean acidity extreme events, identifying hotspots, drivers, and projecting future changes.

Ocean CO₂ uptake at mid-latitudes counteracts CO₂ release in the tropics, but we know little about the effects of marine heatwaves that modulate this process. Here, the authors use joint analysis of satellite measurements, in situ observation, reconstructions derived from machine learning algorithms, numerical model of the global ocean, and find that areas where PMHWs most frequently occur coincide with the regions that are the most critical for the oceanic carbon cycle.

A multi-year marine heat wave in the northeast Pacific warming pool, as the one that occurred from 2019 to 2021, would almost certainly not have occurred in the absence of anthropogenic global warming, according to a climate model-based attribution study.

Giant kelp forests in the Northeast Pacific Ocean are inadequately represented in marine protected areas, which increases their vulnerability to marine heatwaves, according to a 35-year satellite image time series.

Record-high ocean temperatures, combined with a confluence of extreme climate and weather patterns, are pushing the world into uncharted waters. Researchers must help communities to plan how best to reduce the risks.

Of 248 marine heatwaves between 1993 and 2019 in North American and European seas, the effects on fish biomass were often minimal, and the heatwaves were not consistently associated with tropicalization or deborealization.

Surveys of reef change are combined with a unique 20-year time series of land–sea human impacts and the results show that integrated land–sea management could help achieve coastal ocean conservation goals and provide coral reefs with the best opportunity to persist in our changing climate.

Increasing temperatures in the seas around China have a range of physical, biogeochemical and biological impacts. This Review outlines historical and projected changes in these seas and the implications of these changes for marine ecosystems.

This Perspective discusses potential effects of ocean warming on human nutrition provision from coral reef fish, ranging from altered species compositions of fish populations through to changed fish nutrient profiles resulting from altered metabolism, microbiome composition and trophic interactions.

Climate forecast systems are used to develop and evaluate global predictions of marine heatwaves (MHWs), highlighting the feasibility of predicting MHWs and providing a foundation for operational MHW forecasts to support climate adaptation and resilience.

Understanding the impact of future marine heatwaves on coastal ecosystems, which account for most of global fishery catches, is limited due to low-resolution models. Use of high-resolution models shows increases in intensity, and the number of days, of marine heatwaves, endangering resident species.