Regional Associations Respond to Marine Heat Waves

Marine heat waves — persistent and unusual warm temperatures — have once again been in the news this summer and fall, as a mass of warmer-than usual water stretched roughly from Alaska south to California. Observing systems provide long-term data and context for understanding and detecting changes like this in the marine and Great Lakes environments. 

The West Coast research and observing community has been monitoring this warm-water mass closely to predict ecological and economic impacts. The effects on the coastal ocean have varied; at times, the heat was offshore but at other times, high temperatures were found in coastal waters, underscoring the importance of nearshore observations. Resource managers continue to be concerned about this phenomenon and the cascading effects it could have.

The international observing community has recorded marine heat waves in all the world’s oceans, and they have doubled in frequency since 1982. 

In the U.S., the tools we have in place through the Integrated Ocean Observing System (IOOS) — including satellites, buoys, underwater gliders, advanced models and shoreline sensors — play a crucial role in detecting these phenomena when they occur, tracking them over time and providing an early warning alert to resource managers so they can act to protect vital economic resources and fisheries. Long-term data sets that we hold also provide an understanding of ocean changes over time — including showing how current conditions compare to historical averages and detecting anomalies.

Almost all regions are experiencing change.

In Alaska, the Bering Sea has experienced marine heat waves the last two winters. Temperatures in the Gulf of Maine have increased faster than 90 percent of the temperatures in the rest of the world’s oceans and in the Pacific and Caribbean, persistent high sea surface temperatures are contributing to coral bleaching.

By holding a historical record of environmental data and collecting current data and sharing it in real-time or near real-time, our Regional Associations prove their worth again and again — helping society predict and more quickly react to the cascade of other changes likely to occur as oceans continue to warm: more frequent blooms of toxic algae, more acidic oceans, declines in fisheries and more.

What is a Marine Heat Wave?

Marine heat waves (MHW) are prolonged periods of unusually warm water temperatures that can have devastating effects on ecosystems, including species mortalities, changes in the structure and communities within the ecosystem and lowered productivity of fisheries. Marine heat waves have been observed in all oceans over the last decade. 


Heat Waves Have Repercussions

The first time a marine heat wave made national news was one dubbed “The Blob” in 2014-2015. That mass of warm water was the biggest marine heat wave recorded and stretched from California to Alaska. During The Blob, a record outbreak of toxic algae shut down the West Coast Dungeness crab fisheries worth millions of dollars. There were also seabird die-offs, a record numbers of whales entangled in fishing lines, crashing salmon returns and starving California sea lion pups washing up on beaches.

The Blob also had widespread economic and environmental repercussions that we continue to see to this day. 

  • It is the suspected culprit in the massive decline in Pacific cod — 70 percent over two years, which added up to a $100 million annual loss in the fishery;
  • Washington state suspended Chinook salmon fishing last summer;
  • Overall, fish, bird and whale numbers have yet to recover 

While the surface signature of the Blob receded, warmer than average temperatures are still seen at depth and effects have lingered in Alaska and within estuaries like Puget Sound where waters recirculate due to mixing over bathymetric sills.

Marine heat waves can lead to coral bleaching on the reefs of the Caribbean and Pacific Islands.  Loss of Hawaii’s coral could have major economic impacts: One study estimates that Hawaii’s coral reefs provide a $360 million benefit to the state’s economy. Another study commissioned by NOAA showed that estimated total economic value that the American people hold for the coral reefs of the main Hawaiian Islands is $33.57 billion.  

IOOS Regional Associations in Action

In Alaska

Northern latitudes are experiencing the most extreme fluctuations in ocean temperatures.  The Bering Sea in particular is warming rapidly.   For the past two winters, the Bering Sea has experienced marine heat waves that extend throughout the entire water column.  This summer, sea surface temperatures along the Alaskan coast were 4–11 degrees warmer than average. In 2018 and 2019, late winter ice coverage of the Bering Sea was far lower than any winter in the past 170 years, and the duration of ice-free water has now increased to three to four months per year in the Chukchi and Beaufort Seas. 

Data from the Distributed Biological Observatory collaborative shows that the important base of the food chain has been moving north over time while NOAA’s fishery scientists have observed the virtual disappearance of Arctic cod, replaced by Pacific Cod in the northern Bering Sea. Other changes include unusually high numbers of fatalities of seabirds, gray whales and ice seals. The abnormally warm waters are thought to contribute to earlier and more widespread harmful algal blooms.

The Alaska Ocean Observing System (AOOS) maintains observations to validate models for forecasts, including deployment of new assets such as ecosystem moorings, wave buoys, shore-based radars, ecosystem gliders and has developed enhanced sensors, multi-purpose observing platforms and nearshore satellite products.  Citizen science and Indigenous knowledge are key to documenting and understand change.  


Along the West Coast

The west coast Regional Associations — Northwest Association of Networked Ocean Observing Systems (NANOOS)Central and Northern Coastal Ocean Observing System (CeNCOOS) and the Southern California Coastal Ocean Observing System (SCCOOS) work together and with NOAA and other partners to detect and track large-scale oceanographic phenomena like the marine heat waves forming in the Pacific. The Associations provide the nearshore information that complements satellite data collected by NOAA and NASA. They also provide a variety of information products that integrate federal and non-federal data — including climatology tools — that show how current conditions compare with long-term data sets to track variation in the temperatures.  


Buoys like this one on the Oregon coast provide a detailed record of ocean conditions along the nearshore. NANOOS has also developed a “Climatology” app to help users visualize how conditions vary from the long-term average. This plot from the app shows that nearshore observations of sea surface temperatures (black/cyan line) off Oregon were more than two standard deviations above the mean of the 15-year record.  





Regional Associations provide access to satellite and in-water sea surface temperature data to discover marine heat waves and show how current temperatures compare to past conditions. The three Associations operate continuous glider transects off the coast that complement satellite data by providing subsurface observations of heat content.  Such information is important to understanding potential impacts of marine heat waves on fisheries and the proliferation of harmful algal blooms. Here you see track lines of some of these gliders; the data are used to highlight temperature anomalies over the whole depth range — sea-surface to deep. 

Tools such as the California Harmful Algal Bloom Risk Mapping System (C-HARM), developed and supported by SCCOOS, predicts the probability of domoic acid from outbreaks of the toxic algae Pseudo-nitzschia, that may result from warming waters.  Marine heat waves and ocean acidification may be leading to more frequent blooms of toxic algae, which make this capability to assess and track risk extremely important.  Image courtesy of UCSC, SCSD 

For more information: 

Coral Bleaching: Pacific and Caribbean Islands

Warm water can cause coral bleaching and has been tracked in both the Caribbean and Pacific Islands. Measurements from the Pacific Islands Ocean Observing System (PacIOOS) nearshore sensors off the south shore of Oʻahu taken between May and August 2019 showed water temperatures at — or exceeding — the upper level of their recent historical limits, corroborating data seen by NOAA satellites. The PacIOOS data portal also hosts NOAA Coral Reef Watch satellite data, including Sea Surface Temperature Anomalies can be found on PacIOOS Voyager

In Puerto Rico, the CARICOOS buoys record spikes in water temperatures in the nearshore area.  These buoys complement the satellite data collected by NOAA and NASA by providing actual nearshore temperatures.

Along the East Coast

As noted above, the Gulf of Maine is heating up faster than 90 percent of the world’s ocean. The Northeastern Regional Association of Coastal Ocean Observing Systems (NERACOOS) developed the Ocean Climate Display that is used regularly by fishermen, managers, scientists and others to see how current conditions compare to historical and average conditions. The tool helps them understand current and past water temperature data and how it impacts their catch or the fisheries stock.

The Mid-Atlantic Regional Association Coastal Ocean Observing System (MARACOOS) has developed a 10-year mean for the sea surface temperatures from data downloaded directly from the MODIS satellite that is ingested as a datalayer into the MARACOOS data portal. The offshore wind lease areas are shown and the yellow-orange colors indicate the flow of the Gulf Stream as it turns offshore.  

The Southeast Coastal Ocean Observing Regional Association (SECOORA) works with partners at Skidaway Institute of Oceanography, NOAA’s Pacific Marine Environmental Lab and the Grey’s Reef Marine Sanctuary to monitor the long-term change in ocean acidity and its impact on fish habitat.

In the Great Lakes & Gulf of Mexico

All of the Great Lake have warmed at least 1½ degrees since 1995, led by Lake Ontario, which has warmed by more than 2 degrees. The Great Lakes Observing System (GLOS) has buoys that provide water temperature data at the surface and at depth.  And, in the Gulf of Mexico, the Gulf of Mexico Coastal Ocean Observing System (GCOOS)  hosts long-term data sets, supports autonomous underwater vehicle missions, develops tools to combat harmfal algal blooms and more.