Ocean temperatures were the warmest in recorded history in 2019, according to a study published in February's Advances in Atmospheric Sciences.
Using newly available data, scientists ranked ocean temperatures since 1950 to a depth of 2,000 meters and also found the "past five years are the top five warmest years in the ocean historically with modern instruments, and the past 10 years are also the top 10 years on record."
In addition, 2019 was the second-hottest year for air temperatures on record—second only to 2016, according to the National Oceanic and Atmospheric Administration.
"Global temperatures in 2019 were 2 degrees Fahrenheit (1.1 degrees Celsius) warmer than the late 19th century," the agency reported. As with ocean temperatures, the last five years have been the warmest five years on record.
With more than 90 percent of the excess heat from human-emitted greenhouse gases stored in the world's oceans, measuring ocean heat content is one of the best ways to quantify the rate of global warming, scientists who conducted the study suggest.
Amy Snover, director of the University of Washington's Climate Impacts Group said the impacts of a warmer ocean are already being seen off the coast of Washington, as in the rest of the world. "What's interesting is seeing the oceans are warming, not just at the surface—that's been measured for a while. But seeing ocean warming that is penetrating into the ocean is also pretty sobering," she said of the study.
The analysis found that many of the major marine heat waves in recent years have been located near strong ocean heating regions, including the North Pacific, where a heat wave known as The Blob wreaked havoc all along the West Coast from 2014 to 2016. It caused vital parts of the marine food web to crash, which resulted in multiple declared fishery disasters and a massive algal bloom that shut down crabbing and clamming for months. In 2019, the North Pacific's second largest heat wave since 1981 threatened to rival The Blob until it dissipated somewhat.
Heating was distributed throughout the world's oceans, the study said. Higher ocean temperatures reduce dissolved oxygen in the ocean, which significantly affects sea life, the study said. It also increases evaporation, which nourishes heavy rains and promotes flooding and more extreme weather, it said.
According to a new publication, titled "Shifting Snowlines and Shorelines" put out by UW's Climate Impacts Group this month, sea surface temperatures off Washington's coast increased between 0.9 and 1.8 degrees Fahrenheit from 1990 to 2012. "It is virtually certain that ocean warming will continue throughout the 21st century, with the upper ocean expected to absorb 5-7 times more heat than was taken up since 1970," the publication stated.
It also said that by the end of the century under a high greenhouse gas emissions scenario, marine heat waves could occur 50 times more frequently, with 10 times the intensity as they were before 1900.
Snover said the Climate Impacts Group does not have specific numbers for the increasing frequency or intensity of marine heat waves in the North Pacific, but noted that as far as the group's research goes, "we expect those things to happen more often off our coast," she said, adding that under all scenarios, the oceans are expected to continue to warm and marine heat waves are expected to worsen.
The Advances in Atmospheric Sciences article also stated that ocean warming will continue even if air temperatures can be kept at or below 2 degrees Celsius (3.6 degrees Fahrenheit)—as recommended under the Paris Agreement. "However, the rates and magnitudes of ocean warming and the associated risks will be smaller with lower GHG emissions," the article concluded. "Hence, the rate of increase can be reduced by appropriate human actions that lead to rapid reductions in GHG emissions, thereby reducing the risks to humans and other life on Earth."
Ocean warming is also the cause of ocean acidification—a different but also damaging impact that is changing the chemistry of the world's oceans due to the carbon absorption. Snover said hydrogen ion concentrations have increased in Washington's coastal waters by about 26 percent since 1760.
While not a lot of research has evaluated direct impacts of acidification on salmon, two lab studies have shown that the increased acidity slows growth rates in pink salmon, and impairs the sense of smell for coho salmon, hampering their ability to react to predators.
Snover noted that ocean acidification has a negative affect on krill, a major food source for salmon.
The warming and acidifying ocean is just one of many topics in the new Climate Impacts Group publication, which summarizes the September 2019 Intergovernmental Panel on Climate Change's special report on the ocean and cryosphere, and examines impacts in Washington state.
The cryosphere comprises frozen portions of the earth that are at or below the land and ocean, including snow, glaciers, ice sheets, sea and river ice and frozen ground. "Ten percent of the Earth's land area is covered by glaciers or ice sheets, which, together with permanent snow, contain about 69 percent of the Earth's freshwater," the publication states.
In Washington, glaciers in the North Cascades decreased 56 percent between 1900 and 2009; spring snowpack has declined on average by about 30 percent from 1955 to 2016; and that snowpack is melting earlier in the spring—by up to 20 days in the snow-dominated watersheds of Puget Sound, according to the publication.
Snover noted that in the Columbia Basin, North Cascade glaciers help maintain streamflows in the summer, which is the system's low-flow period. "Salmon are most vulnerable to the low flows and warm temperatures," she said. And while the snowpack has always been variable from year to year, a long-term decline has numerous implications for recreation, snow-dependent wildlife, and the environment.
"The snowpack is our natural reservoir of water that transfers from the wet winter months to the dry summer months," she said, concluding, "People—and animals and fish—are adapted to a certain amount and timing of water availability." With a warming climate, the Pacific Northwest can expect more summers like 2015, when drought and low water conditions mimicked future conditions under global warming.
The article concluded, "With everyone on Earth connected to the ocean or cryosphere, we all stand to lose from continued warming. This means that we will all benefit from immediate action to prevent further warming and to prepare for the impacts of a climate-changed world. The choice is ours. The time is now."
Snover said the Climate Impacts Group has been working for almost 25 years to both encourage reductions in greenhouse gases, and to motivate and support preparing for a changing climate.
"There are two sides of the coin. There's preventing the problem from getting worse, or reducing emissions, and preparing for impacts that we set in motion," she said. "We have said that for these 25 years—you can't split the coin in half. They both need to be dealt with. I think what's changed is that people are beginning to recognize these changes are going to occur much sooner than they had thought. These are serious, and they're in the time frame we ought to be preparing for them."