Top: Burke Hales (Photo: Don Frank).
Bottom: George Waldbusser (Photo: Oregon Sea Grant
Editor’s Note: This issue of The Climate CIRCulator spotlights not one, but two researchers in the same profile. To see why, read on.
Waldbusser and Hales Join Up to Study
You could think of Oregon State University scientists George Waldbusser and Burke Hales as the Lennon and McCartney of climate science. Like the two Beatles icons, their collaboration works precisely because of their differences. They bring a synergy of talents to their research that allows for unique insights.
Hales is a chemist, Waldbusser a biologist. For the past five years their divergent interests have united around studying ocean acidification and its effects on marine organisms. Together, the two have coauthored three papers, with another four currently in the works. (Their most recent paper is reviewed in this issue of the CIRCulator
; see “The Role of Saturation in Seashell Formation.”)
Ocean acidification is the common name for what happens when carbon dioxide from fossil fuels dissolves in seawater, lowering the water’s pH, with deleterious results for shell-forming creatures. To date, most acidification research has revolved around the broader ocean. But scientists have discovered that many estuaries — including those along the Pacific Northwest coast — act as “hotspots” where the effects of acidification are intensified. (See the June/July 2014 CIRCulator
.) Waldbusser and Hales’ work has focused largely on these estuaries. Because of the ecological and economic importance of estuaries, Hales says it’s high time we start paying attention to them.
“We really can’t think of ocean acidification in terms of a quiescent blue ocean with a slow-moving baseline response,” says Hales, who has studied the carbonate chemistry of estuaries for over two decades. “Most of the places where sensitive organisms live are in estuaries, not in the open ocean.”
“The way I think about it is, you have these big global changes,” he says. “And then you have all these other factors happening in the estuaries. The one doesn’t preclude the other.”
One estuary that caught the researchers’ eyes is Oregon’s Netarts Bay. There in 2007, workers at the Whiskey Creek Shellfish Hatchery noticed that their Pacific oyster larvae were dying en masse. Hales and Waldbusser later would pin the deaths on ocean acidification.
At Whiskey Creek, Hales and Waldbusser worked closely with each other and the hatchery to develop a monitoring and treatment program for the bay water used for raising larvae. The system was lovingly named the “Burkelator” after Hales. From the hatchery, further collaborations would develop.
Hales and Waldbusser’s current work includes:
- Developing stress models to characterize how larvae respond to acidification
- Examining the carbonate chemistry inside and outside seagrass beds and how that might help or hurt oysters and clams
- Additional water quality examinations at multiple oyster hatcheries in the region
- Developing a mechanistic understanding of larval bivalve responses to acidification.
Hales says his collaboration with Waldbusser has worked in large part because Waldbusser has an extensive background in biochemistry. For his part, Waldbusser says Hales has learned to think like a biologist. This has allowed the two to seamlessly converge both biological and chemical aspects of their work.
“For an experimental biologist, George has a chemist’s rigor,” says Hales. “He’s been able to carry out biological measurements that look like chemical measurements.”
Waldbusser puts it this way: “Our expertise and backgrounds are very complementary. We get along pretty well, too.”
A model based on ocean and atmosphere interactions (Photo: NOAA) [Click on image for enlarged view]
Climate scientists — including those of us at OCCRI — use global climate models to understand the range of possible futures. Dozens of research groups produce hundreds of simulations, which may differ in their greenhouse-gas emission scenarios as well as their starting conditions for each simulation.
Global Climate Modeling
New Accounting Method
For Sources of Uncertainty
Thus, interpretation can be challenging. Translating these simulations into estimates of change - including the range or distribution of specific changes (e.g., 1°-5°C) - is especially difficult, complicated further when some modeling groups provide one simulation while others provide 10.
Now, researchers Paul Northrop and Richard Chandler of the University College of London address this problem by offering a consistent framework that includes all available simulations and sorts out the role for each source of difference: emissions scenario, choice of climate model, and initial conditions. They apply their framework for temperature change both globally and across 22 regions, including western North America.
The researchers found that variability is linked more strongly to the choice of global climate model than to different emissions scenarios earlier in the current century (2020-49). But scenario variations dominate later in the century (2069-89). They also found that variations across runs for the same model are important early in the century, but variations across runs are not important late in the century, nor in the global mean.
For precipitation changes in western North America, they found that variations across runs are the most important factor earlier in the century, followed closely by scenarios. Toward the end of the century, this order reverses, but variations across runs are still important. Variations associated with GCMs are fairly unimportant both early and late in the century.
Current snow water equivalent, National Water and Climate Center (USDA/NRCS
) [Click on map for enlarged view]
You’ve probably noticed there isn’t much snow in the Cascades this winter. The reason is temperature.
Mountain Snowpack 2015
Warm, Rainy Cascades Winter
Means Scarce Summer Water
Winters in the Pacific Northwest are typically wet. This winter has been no exception. Precipitation has been above normal for Oregon, Washington and Idaho since the start of the water year on October 1.
Temperatures, too, have been above normal. So despite the high precipitation, snowpack in Oregon and Washington’s Cascade Mountains are at a near-record low for this time of year. In fact, mid-January snow-water equivalent in the Oregon Cascades was less than a quarter of normal, according to the National Resources Conservation Service. In Washington, the snow-water equivalent was only slightly higher, reported the service, the federal agency responsible for monitoring precipitation and snowpack in the Pacific Northwest. It’s a similar story elsewhere in the region.
Except for skiers and snowboarders, why should anyone care if precipitation falls as rain and not snow? The answer is summer water availability. Across the West, many communities rely on snowpack as a kind of natural reservoir. Less snow spells a smaller reserve when it’s needed most during the hot, dry summer.
For a glimpse of what next summer might look like, we need look no farther than last year’s records when low snowpack plagued most of the Northwest. Southern Oregon, for example, experienced severe drought conditions.
Avoiding last year’s fate is still possible. An active late-winter/early-spring pattern could bring big snows to the mountains. But it’s looking like that might not happen. The temperature outlook from the National Oceanic and Atmospheric Administration’s Climate Prediction Center for the remainder of this winter shows increased odds of above-average temperatures in Oregon and Washington.
Here’s hoping for some late-season snow.
Oyster bucket (Photo: Michael Monroe, Oregon Sea Grant)
From the corals of Australia’s Great Barrier Reef to the shellfish hatcheries of the Pacific Northwest, ocean acidification’s effects on shell-forming organisms are now well documented. However, ocean acidification research has tended to focus on just one aspect of the phenomenon’s chemistry: pH.
The Role of Saturation in Seashell Formation
Now, a new study suggests pH alone isn’t telling the whole story.
The study by Oregon State University researchers George Waldbusser, Burke Hales, Chris Langdon, and Brian Haley looks at the responses of Pacific oysters and Mediterranean mussel larvae under varying conditions of acidification. The team’s results suggest that past researchers’ penchant for pH has led to another important chemical measure being ignored: the saturation state.
Essentially, the saturation state is a way to quantify how much material — various forms of calcium carbonate ions — is available in seawater for organisms to build shells. The saturation state is closely linked to pH and alkalinity. (Low pH generally spells a lower saturation state with less calcium carbonate.) And both pH and the saturation state are closely linked to how much carbon dioxide has dissolved in the water.
This close link, or coupling, could be why past research had ascribed so much importance to low pH. Perhaps, the OSU researchers conjecture, previous investigations might have attributed to low pH the effects of the saturation state? If this error has been made, it’s easy enough to see why.
In the real world, ocean acidification occurs when carbon dioxide from fossil fuels dissolves in seawater. This lowers the water’s pH levels, rendering the water less basic and more “acidic.” Consequently, shell-forming creatures — be they mollusks or corals — have trouble forming their shells.
The reason for the organisms’ difficulties has long been blamed on dropping pH, with past research concluding that low pH waters make it difficult for some organisms to regulate their internal chemistry. (Effectively, the organisms themselves were becoming less basic and more acidic.) But the new study says that’s only a piece of it.
To discover what roles pH, the saturation state, and dissolved CO2 each play, the researchers set about decoupling the three factors experimentally. They did this by fiddling with the alkalinity of their seawater. Once decoupled, the researchers then subjected their larvae to differing levels of the three factors. Their data suggest that the saturation state was a significantly larger determinant of health and mortality for their larvae than pH or CO2. (Low pH was still a factor, but only at extremely low levels.)
The reason, the researchers conjecture, is that the tiny shell-makers were basically scrambling to build their shells before they ran out of energy. (Pacific oyster larvae, for instance, have a mere 48-hour window to form their initial shells — essential for growing swimming and feeding appendages — before the energy stored in the eggs runs out.) Consequently, if the saturation state is low enough, the energy needed to build shells before it’s too late becomes very high, and the larvae either fail to develop or become stunted.
Iria Gimenez, a student of Waldbusser and Hales, is now in the process of expanding this research into a working stress model of how oyster larvae are impacted by the variable conditions in coastal waters throughout the larval period in response to dissolved CO2, pH, and the saturation state.
Waldbusser, G.G., B. Hales, C.J. Langdon, B.A. Haley, P. Schrader, E.L. Brunner, M.W. Gray, C.A. Miller & I. Gimenez (2014). Saturation-state sensitivity of marine bivalve larvae to ocean acidification, Nature Climate Change, doi:10.1038/nclimate2479
Klamath National Wildlife Refuge during the 2001 drought (Photo: USGS
A new paper published in the Journal of Climate suggests that the risk of decade-long droughts, like the Dust Bowl in the 20th century, may be greater than previously estimated.
Are “Dust Bowls” More Likely under Climate Change?
The greatest risk is in the Southwest United States, where the likelihood of these droughts occurring once every 50 years is possibly greater than 80 percent with increasing greenhouse gases. The risk of “megadroughts” — those that last for multiple decades — also increase in the Southwest from nearly zero up to 50 percent by the late 21st century.
In this study, records of past drought from instrumental observations and paleoclimate records, such as tree rings that may go back thousands of years, are combined with projections of future precipitation from 27 global climate models from the Coupled Model Intercomparison Project (phase 5). This method, the authors argue, provides a more robust estimate of drought by considering both internal drivers of drought, along with influences from future greenhouse gas emissions.
The silver lining, at least for the Pacific Northwest, is that megadroughts are much less likely, increasing from nearly zero under present-day conditions to 20 percent by the end of the century under the worst greenhouse gas scenario. The study even suggests that the risk of decadal drought in the Pacific Northwest, with a 50 percent to 60 percent chance of occurring today, actually decreases to 20 percent to 30 percent under increasing greenhouse gases.
These findings should be taken with caution, though, since unlike other regions, precipitation in our region is not expected to change markedly. The greater risk for the Northwest is the transition of precipitation from snow to rain in the mountains as temperatures rise. Similar to 2014 (and the way 2015 is shaping up), this change will likely increase our streamflows during winter when less water is needed, at the cost of spring and summer streamflows when demand is greatest.
Ault, T.R., J.E. Cole, J.T. Overpeck, G.T. Pederson, & D.M. Meko (2014) Assessing the Risk of Persistent Drought Using Climate Model Simulations and Paleoclimate Data. J. Climate
As the El Nino-induced pattern shifts eastward, rainfall anomalies are expected to intensify on the West Coast of North America.
As the planet warms, some patterns of natural climate variability - notably El Niño - may also change.
Modulating Climate Change in North America
A team of climate scientists in China and California wanted to disentangle the role of El Niño from all the other factors in climate change. So they posed the following question: “How much of the pattern of climate change would be the same if the sea-surface temperature pattern remained the same?”
The team, led by Zhen-Qiang Zhou of the Ocean University of China, used climate models representing the ocean and the atmosphere to explore the impact of global warming on El Niño-induced patterns of temperature and precipitation across the Pacific Ocean and North America. For the study, the researchers used a “composite” El Niño, the average winter sea-surface temperatures during four El Niño events in the Northern Hemisphere (1972-1973, 1982-1983, 1997-1998 and 2009-2010). They were interested in possible changes in atmospheric “teleconnections,” or statistical correlations, between North American climate and El Niño (the more technical term is El Niño-Southern Oscillation or ENSO).
The researchers found that, indeed, teleconnections may shift. ENSO-induced changes in eastern Pacific tropical thunderstorms — along with warmer northern Pacific sea-surface temperatures — affect precipitation on the U.S. West Coast, making it more variable and more intense. Land-surface temperature, too, was more variable and intense moving eastward across the United States, a result of migration of the Pacific North American Pattern.
The models used in their study have better spatial resolution and exhibit better distribution of El Niño sea-surface warming than other models using only mean global sea-surface warming. Also, isolating atmospheric factors shows larger anomalies for the “forced” versus “internal” Pacific North American Pattern mode. Finally, greater magnitude in changes in sea-surface temperature and El Niño teleconnections producing an eastward shift in U.S. temperatures will persist in the future, likely independent of climate-change effects on El Niño variability and behavior.
A caveat: By holding the El Niño sea-surface temperature pattern identical for present and future climate simulations, the study sidesteps major uncertainties in El Niño properties (such as amplitude and sea-surface temperature).
Zhou, Z.-Q., S.-P. Xie, X.-T. Zheng, Q. Liu, & H. Wang (2014). Global Warming–Induced Changes in El Niño Teleconnections over the North Pacific and North America, J. Climate
, 9050–9064. doi: doi.org/10.1175/JCLI-D-14-00254.1
The Climate CIRCulator is brought to you by The Pacific Northwest Climate Impacts Research Consortium (CIRC). CIRC delivers science, information, and tools to decision makers responsible for the management of resources and services in a changing climate. Our team consists of experts from Oregon State University, the University of Oregon, the University of Idaho, and the University of Washington. CIRC is funded by the National Oceanic and Atmospheric Administration (NOAA) and housed in the Oregon Climate Change Research Institute (OCCRI) at Oregon State University. The OCCRI brochure can be downloaded here.