What's New Archive

The ocean is the flywheel that propels the climate system, storing huge amounts of heat and carbon in a vast reservoir that covers 70 percent of Earth’s surface. Measuring changes in that heat content over time has been a subject of intense scientific research, with analyses growing more precise as observing systems expand and the duration of measurements grows. In a new article published in the journal Nature Climate Change, Gregory Johnson and John Lyman with PMEL's Large Scale Ocean Physics group analyzed four prominent ocean temperature datasets and found that over the past 52 years, the number of ocean regions showing long-term warming trends dwarfs the regions showing cooling trends.

“Ocean warming is tightly linked to increases in atmospheric greenhouse gases concentrations, so global ocean temperature trends are an important yardstick for measuring climate change,” said Johnson. “We noticed that as the time-series of upper ocean heat content we were analyzing grew over the years, more of the ocean area was covered by a statistically significant warming trend.”

Johnson and Lyman decided to step back and look at how temperature trends changed when estimated over varying time periods. To investigate those questions, the pair generated annual maps of ocean heat content anomalies in the upper 700 meters of ocean from 1993 to 2019 by combining sea-level data from satellite altimeters with ocean temperature data. They also analyzed annual maps of ocean temperature data from the upper 700 meters from 1968 to 2019 from three other research groups: NOAA’s National Center for Environmental Information, the Japan Meteorological Agency, and the Chinese Academy of Science’s Institute of Atmospheric Physics. 

For the 27-year period 1993 to 2019, they found 53 percent of the global ocean exhibited statistically significant warming trends versus 3 percent of the ocean showing significant cooling trends. For the 52-year period from 1968 to 2019, the imbalance grew markedly: 72 to 79 percent of the ocean area showed warming, while only 1 to 3 percent exhibited cooling. When trends were estimated over shorter 5-year periods, the areas and imbalances were much smaller, with 24% warming and 17% cooling. 

While the ocean has soaked up the overwhelming majority of greenhouse warming, it hasn’t come without a cost. Warmer water occupies more space than cooler water, and about 42 percent of sea level rise documented since 1993 is due to thermal expansion caused by global warming. Rising ocean temperatures are also associated with increased marine heatwaves, which in turn can devastate coral reefs, dislocate or disrupt distributions of important fish species, and increase vertical ocean stratification, which reduces nutrients in surface water, and decreases dissolved oxygen at depth, both of which affect ecosystems, fisheries, and possibly even ocean carbon storage. Rising ocean temperatures can also influence changes in the climate and promote rapid intensification of tropical cyclones. 

Read the full article on NOAA Research. 

Three saildrones left Alameda, California in May and have arrived at Unimak Pass in Alaska’s remote Aleutian Islands. The ocean drones have sailed nearly 2,700 miles at a walking pace, about 2.5 miles per hour (2 knots), which is just about the distance from Seattle to Miami. Once they navigate through the pass, the saildrones will enter the Bering Sea. This is where they will conduct a two month-long acoustic survey of walleye pollock to collect some critically needed data to support management of the nation’s largest commercial fishery for Alaska pollock. They are expected to reach their first survey station in about a week and will cover roughly the same area normally covered by standard research vessels.

The data the drones collect will help to fill in the gap for fisheries stock assessment scientists who monitor the changes in pollock populations to advise fisheries management. The sonar measurements made by the ocean drones will provide valuable insights on pollock abundance and distribution in 2020. 

The mission is led by NOAA's Alaska Fisheries Science Center with scientists at the Pacific Marine Environmental Laboratory processing the oceanographic and meteorological data in real time. Data will be made available to weather forecasts center worldwide via the World Meteorological Organization's Global Telecommunication System (GTS) so that these observations can be incorporated into weather predictions. PMEL, AFSC and Saildrone have collaborated on several missions in the Arctic since 2015 to develop the vehicle’s capabilities and refine the sensors.

New NOAA and partner research comparing ocean acidification around North America shows that the most vulnerable coastal waters are along the northern part of the east and west coasts. While previous research has looked at specific regions, the new study appearing in Nature Communications, is the first in-depth comparison of ocean acidification in all North American coastal ocean waters. 

“Ocean acidification is everywhere, but this synthesis basically shows that, depending on the location, it can manifest very differently,” said Wei-Jun Cai, lead author and a professor at the University of Delaware School of Marine Science and Policy. 

Ocean acidification, a global process in which the ocean absorbs carbon dioxide from the atmosphere, is occurring faster than at any time in the past 50 million years. The global rise in ocean acidity is fueled by human-created greenhouse gases. An estimated 25 percent of those emissions are absorbed by the ocean.

In the ocean waters off the United States east coast, the northbound Gulf Stream current brings warm waters from the tropics while the southbound Labrador Current brings cold waters from the Arctic and subarctic regions. The colder ocean temperatures along the northern part of the east coast take up more carbon dioxide from the atmosphere than do warmer waters along the southern east coast and Gulf of Mexico. This uptake of carbon dioxide accelerates ocean acidification, which can hamper the ability of shellfish, corals and other valuable marine species to build their shells and thrive.

On the west coast, ocean acidification is affecting the waters of the California Current, which extends from the United States - Canadian border to Baja California. The California Current is characterized by strong, cold currents, and wind-driven upwelling events. Upwelling brings colder, carbon-dioxide-rich subsurface waters to the ocean’s surface to replace surface water that has been pushed away by winds.

“The water from the subsurface has low pH and high carbon dioxide, which causes stress to the biological system,” said co-author Richard Feely of NOAA’s Pacific Marine Environmental Laboratory (PMEL). “So the combination of the uptake of anthropogenic carbon dioxide from the atmosphere and the upwelling of CO2-rich low-pH water from below leads to enhanced acidification in this region.”

The research team from NOAA, the University of Delaware, and scientists from Canada, Mexico, the United Kingdom, China and Taiwan based the new findings on data gathered during several research cruises between 2007 and 2018. A number of those cruises were led or supported by NOAA’s Pacific Marine Environmental Lab, Atlantic Oceanographic and Meteorological Lab and the Ocean Acidification Program. Other PMEL authors include Simone Alin, Jessica Cross, Brendan Carter (UW/JISAO) and Adrienne Sutton.

Read the full news release from the University of Delaware.

Read the paper in Nature Communications (an open access journal): Controls on surface water carbonate chemistry along the North American ocean margins

The main tsunami hazard for Washington State originates from a potential earthquake at the Cascadia Subduction Zone, which is stretched along the U.S. Pacific coasts offshore Washington, Oregon and Northern California. The main impact during such a tsunami event would be the ocean-side communities on the open coast. However, Washington State’s main population centers are located along Puget Sound, a long narrow inlet over 100 miles away from open coast and from potential Cascadia earthquake.  

Recent tsunami mapping and tsunami hazard modeling efforts of the National Tsunami Hazard Mitigation Program have demonstrated that a Cascadia tsunami impact could be significant even for the coasts deep inside Puget Sound. Due to this need, the NOAA Center for Tsunami Research (NCTR) at PMEL developed high resolution tsunami inundation forecast models for Bellingham and Tacoma, Washington. These high-resolution community models are needed to improve the accuracy of the tsunami forecasts at NOAA’s Tsunami Warning Centers. Since 2012, NCTR has developed over 75 high-resolution inundation forecast models for the most vulnerable U.S. coastal communities and that number continues to grow. 

While the tsunami wave amplitudes in Bellingham and Tacoma are expected to be lower in comparison with the outer coast communities during a Cascadia tsunami, the population density and potential local tsunami-genic faults within Puget Sound make these two cities high tsunami risk. Seattle would also see some impact but was not found to be as high risk from tsunami inundation as Tacoma or Bellingham.