Posts Tagged marine heatwave

Sep 5 2019

New Marine Heatwave Emerges off West Coast, Resembles “the Blob”

Researchers are monitoring a new marine heatwave off the West Coast for effects on the marine ecosystem.

Sea surface temperature anomaly maps show temperatures above normal in orange and red.

 

About five years ago “the Blob” of warm ocean water disrupted the West Coast marine ecosystem and depressed salmon returns. Now, a new expanse of unusually warm water has quickly grown in much the same way, in the same area, to almost the same size.

The warm expanse building off the West Coast stretches roughly from Alaska south to California. It ranks as the second largest marine heatwave in terms of area in the northern Pacific Ocean in the last 40 years, after “the Blob.”

“It’s on a trajectory to be as strong as the prior event,” said Andrew Leising, a research scientist at NOAA Fisheries’ Southwest Fisheries Science Center in La Jolla, California. He developed a system for tracking and measuring heatwaves in the Pacific Ocean using satellite data. “Already, on its own, it is one of the most significant events that we’ve seen.”

Cold water welling up from ocean depths along the coast has so far held the warm expanse offshore, he said. However, the upwelling, driven by coastal winds, usually wanes in the fall. The heatwave could then move onshore and affect coastal temperatures, he said. This already appears to have happened along the coast of Washington.

The new marine heatwave off the West Coast stands out in this map of sea surface temperature anomalies, with darker red denoting temperatures farther above average. The highest temperatures shown are more than 5 degrees Fahrenheit above average. Image from NOAA Coral Reef Watch, which corrects effectively for cloud cover.

NOAA Fisheries is focusing additional monitoring on the new heatwave, designated the Northeast Pacific Marine Heatwave of 2019. NOAA Fisheries’ Southwest and Northwest Fisheries Science Centers will provide fisheries managers and others with information on how the unusually warm conditions could affect the marine ecosystem and fish stocks.

“We learned with ‘the Blob’ and similar events worldwide that what used to be unexpected is becoming more common,” said Cisco Werner, NOAA Fisheries Director of Scientific Programs and Chief Science Advisor. “We will continue to inform the public about how the heatwave is evolving, and what we might anticipate based on experience.”

The new heatwave resembles the early stages of “the Blob.” This previous marine heat wave peaked through 2014 and 2015 with temperatures close to seven degrees Fahrenheit above average.

Blob Could Dissipate Quickly

Like “the Blob,” the new heatwave emerged over the past few months. A ridge of high pressure dampened the winds that otherwise mix and cool the ocean’s surface. The heatwave remains relatively new and is primarily affecting the upper layers of the ocean, it could break up rapidly.

“It looks bad, but it could also go away pretty quickly if the unusually persistent weather patterns that caused it change,” said Nate Mantua, a research scientist at the Southwest Fisheries Science Center.

Current forecasts show the heat wave moderating but continuing for months.

A key question is whether the new heatwave will last long enough to affect the marine ecosystem. Biologists say that its large size means it probably already has. For example, warmer conditions during “the Blob” left lesser-quality food available to young salmon entering the ocean. It also shifted predator distributions in ways that contributed to low returns of salmon.

Shifts in the marine food web during the evolution of the 2014-2015 marine heatwave called, “the Blob,” forced sea lion mothers to forage further from their rookeries in the Channel Islands off Southern California. Hungry pups set out on their own, but many became stranded on area beaches. 

Other impacts linked to the earlier heatwave include:

  • The largest harmful algal bloom recorded on the West Coast, which shut down crabbing and clamming for months.
  • Thousands of young California sea lions stranding on beaches.
  • Multiple declared fishery disasters.

NOAA Fisheries scientists recently convened a special meeting to discuss the emerging heatwave and how to anticipate and track its effects. They are now reviewing impacts documented during the “the Blob” to compare them against the effects of the emerging heatwave.

“Given the magnitude of what we saw last time, we want to know if this evolves on a similar path,” said Chris Harvey, a research scientist at the Northwest Fisheries Science Center.

Monitoring Framework in Place

NOAA Fisheries’ two West Coast laboratories collaborate on the California Current Integrated Ecosystem Assessment. This is a joint effort to track and interpret environmental change off the West Coast. That provides a framework to monitor shifting conditions, Harvey said.

One challenge will be applying lessons learned from the last heat wave to anticipate and mitigate potential impacts of the new one. For example, the warm water of “the Blob” led humpback and other whales to feed closer to shore. Record numbers became entangled in lines from crab traps and other fishing gear.

In response, fishermen, managers, and others have formed working groups in California, Oregon, and Washington. They hope to find ways of reducing the risk of entanglements.

The marine heatwave that has formed off the West Coast of North America is currently close to the warmest area in the Pacific Ocean. Map shows sea surface temperature anomalies, with darker orange representing temperatures farther above average. Image from NOAA National Environmental Satellite, Data, and Information Service.

 

Real-time research on environmental changes will give managers the details they need to respond, said Kristen Koch, Director of the Southwest Fisheries Science Center. “This is a time when we all need to know how our marine ecosystem is changing, and what that means for those of us who live along the West Coast.”

The new northeast Pacific heatwave reflects current weather patterns. This includes a band of high pressure stretching north to the Bering Sea and Alaska, which have been unusually warm in recent years, said Nick Bond, a research meteorologist with the Joint Institute for the study of the Atmosphere and Ocean in Seattle, a collaboration between NOAA and the University of Washington.

“There are definitely concerning implications for the ecosystem,” said Bond, who is credited with naming “the Blob.” “It’s all a matter of how long it lasts and how deep it goes.”

Original post: https://www.fisheries.noaa.gov/feature-story/new-marine-heatwave-emerges-west-coast-resembles-blob

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Jun 3 2018

Marine heatwaves are getting hotter, lasting longer and doing more damage

Marine heatwaves occur everywhere in the ocean. Credit: Eric Oliver/Dalhousie University

On land, heatwaves can be deadly for humans and wildlife and can devastate crops and forests.

Unusually warm periods can also occur in the ocean. These can last for weeks or months, killing off kelp forests and corals, and producing other significant impacts on marine ecosystems, fishing and aquaculture industries.

Yet until recently, the formation, distribution and frequency of marine heatwaves had received little research attention.

Long-term change

Climate change is warming ocean waters and causing shifts in the distribution and abundance of seaweeds, corals, fish and other marine species. For example, tropical fish species are now commonly found in Sydney Harbour.

But these changes in ocean temperatures are not steady or even, and scientists have lacked the tools to define, synthesize and understand the global patterns of marine heatwaves and their biological impacts.

At a meeting in early 2015, we convened a group of scientists with expertise in atmospheric climatology, oceanography and ecology to form a marine heatwaves working group to develop a definition for the phenomenon: A prolonged period of unusually warm water at a particular location for that time of the year. Importantly, marine heatwaves can occur at any time of the year, summer or winter.

With the definition in hand, we were finally able to analyze historical data to determine patterns in their occurrence.

Analysis of marine heatwave trends

Over the past century, marine heatwaves have become longer and more frequent around the world. The number of marine heatwave days increased by 54 per cent from 1925 to 2016, with an accelerating trend since 1982.

We collated more than 100 years of sea surface temperature data around the world from ship-based measurements, shore station records and satellite observations, and looked for changes in how often marine heatwaves occurred and how long they lasted.

We found that from 1925 to 1954 and 1987 to 2016, the frequency of heatwaves increased 34 per cent and their duration grew by 17 per cent.

These long-term trends can be explained by ongoing increases in ocean temperatures. Given the likelihood of continued ocean surface warming throughout the 21st century, we can expect to see more marine heatwaves globally in the future, with implications for marine biodiversity.

‘The Blob’ effect

Numbers and statistics are informative, but here’s what that means underwater.

 

Yearly count of marine heatwave days from 1900 to 2016, as a global average. Credit: Eric Oliver/Dalhousie University

A marine ecosystem that had 30 days of extreme heat in the early 20th century might now experience 45 days of extreme heat. That extra exposure can have detrimental effects on the health of the ecosystem and the economic benefits, such as fisheries and aquaculture, derived from it.

A number of recent marine heatwaves have done just that.

In 2011, a marine heatwave off western Australia killed off a kelp forest and replaced it with turf seaweed. The ecosystem shift remained even after water temperatures returned to normal, signalling a long-lasting or maybe even permanent change.

That same event led to widespread loss of seagrass meadows from the iconic Shark Bay area, with consequences for biodiversity including increased bacterial blooms, declines in blue crabs, scallops and the health of green turtles, and reductions in the long-term carbon storage of these important habitats.

Similarly, a marine heatwave in the Gulf of Maine disrupted the lucrative lobster fishery in 2012. The warm water in late spring allowed lobsters to move inshore earlier in the year than usual, which led to early landings, and an unexpected and significant price drop.

More recently, a persistent area of warm water in the North Pacific, nicknamed “The Blob”, stayed put for years (2014-2016), and caused fishery closures, mass strandings of marine mammals and harmful algal bloom outbreaks along the coast. It even changed large-scale weather patterns in the Pacific Northwest.

As global ocean temperatures continue to rise and marine heatwaves become more widespread, the marine ecosystems many rely upon for food, livelihoods and recreation will become increasingly less stable and predictable.

The climate change link

Anthropogenic, that is human-caused, climate change is linked to some of these recent marine heatwaves.

For example, human emissions of greenhouse gases made the 2016 marine heatwave in tropical Australia, which led to massive bleaching of the Great Barrier Reef, 53 times more likely to occur.

Even more dramatically, the 2015-16 marine heatwave in the Tasman Sea that persisted for more than eight months and disrupted Tasmanian fisheries and aquaculture industries was over 300 times more likely, thanks to anthropogenic climate change.

For scientists, the next step is to quantify future changes under different warming scenarios. How much more often will they occur? How much warmer will they be? And how much longer will they last?

Ultimately, scientists should develop forecasts for policy makers, managers and industry that could predict the future impacts of marine heatwaves for weeks or months ahead. Having that information would help fishery managers know when to open or close a fishery, aquaculture businesses to plan harvest dates and conservation managers to implement additional monitoring efforts.

Forecasts can help manage the risks, but in the end, we still need urgent action to curb greenhouse gas emissions and limit global warming. If not, marine ecosystems are set for an ever-increasing hammering from extreme ocean heat.

More information on this and related studies can be found on www.marineheatwaves.org.

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