Ecology, Climate Change and Related News

Conservation Science for a Healthy Planet

Tag Archive: drought

  1. Snowpack Near Record Lows Spells Trouble for Western Water Supplies

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    • Scientists say snow seasons like the U.S. West is experiencing now will become more common as global temperatures rise, and economic costs will go up, as well.
  2. Study predicts a significantly drier world if global warming reaches 2ºC

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    • Limiting warming to under 1.5ºC would dramatically reduce the fraction of the Earth’s surface that undergoes such changes.

    January 1, 2018 University of East Anglia Read full ScienceDaily article here

    New research predicts a significantly drier world if global warming reaches 2ºC. Over a quarter of the world’s land could become significantly drier and the change would cause an increased threat of drought and wildfires.

    The change would cause an increased threat of drought and wildfires.

    But limiting global warming to under 1.5C would dramatically reduce the fraction of the Earth’s surface that undergoes such changes. Areas which would most benefit from keeping warming below 1.5ºC include Central America, Southern Europe, Southern Australia, parts of South East Asia, and Southern Africa.

    …Dr Chang-Eui Park….one of the authors of the study, said: “Aridification is a serious threat because it can critically impact areas such as agriculture, water quality, and biodiversity. It can also lead to more droughts and wildfires — similar to those seen raging across California.

    “Another way of thinking of the emergence of aridification is a shift to continuous moderate drought conditions, on top of which future year-to-year variability can cause more severe drought.

    Chang-Eui Park, et al. Keeping global warming within 1.5 °C constrains emergence of aridification. Nature Climate Change 8, 70–74 (2018). doi:10.1038/s41558-017-0034-4

  3. Winter rains make SF Bay less salty, knocking back some invaders

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    • Dry and wet periods drive rapid shifts in community assembly in an estuarine ecosystem.
    • Chang’s team also found that a couple native species did better in wet years too. This suggests with the right strategy, managers could use the situation to help native species instead.

    December 7, 2017  Smithsonian Read full ScienceDaily article here

    For many Californians, last year’s wet winter triggered a case of whiplash. After five years of drought, rain from October 2016 to February 2017 broke more than a century of records. In San Francisco Bay, biologists discovered a hidden side effect: All that freshwater rain can turn the tables on some of the bay’s invasive species….

    …During dry years, when bay waters remained salty, one invader dominated above all others: the invasive tunicate Ciona robusta. A translucent, vase-shaped filter feeder from Asia, Ciona has invaded five continents, including North America’s West Coast. It has a reputation for crowding out other species, thanks to its rapid growth, and similar Ciona species have thrown a wrench into shellfish aquaculture.

    But when the wetter winters of 2006 and 2011 hit, Ciona and other solitary tunicates like it were unable to cope with the massive influxes of freshwater. In their place, mat-like colonial tunicates and encrusting bryozoans took over….

    Andrew L. Chang, Christopher W. Brown, Jeffrey A. Crooks, Gregory M. Ruiz. Dry and wet periods drive rapid shifts in community assembly in an estuarine ecosystem. Global Change Biology, 2017; DOI: 10.1111/gcb.13972

  4. 2017’s Ridiculously Resilient Ridge & the North American Winter Dipole

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    • Persistent western ridge and eastern trough next 2+ weeks–warm in the west, cool in the east– linked to western tropical Pacific ocean warming
    • Tropical warmth (in the West Pacific) and coolness (in the East Pacific) are both linked to different patterns of North Pacific winter ridging, and may offer an early warning of seasons with an elevated risk of dry conditions in California.
    • “Warm West/Cool East” extremes have become more common in recent years
    • this increase in contrasting dipole extremes appears to be caused primarily by the increased rate of warming in the western U.S. relative to the eastern U.S

    Daniel Swain December 4 2017 Read full WeatherWest blog here

    Origins of the [Ridiculously Resilient Ridge or] “Triple R” and California’s severe drought

    In 2013, a curious feature began to emerge on the weather maps: a region of unusually high atmospheric pressure (known as a “ridge” in meteorological circles) was consistently pushing the Pacific jet stream to the north of California, resulting in very dry conditions. At the time, I (somewhat jokingly) termed this anomalous high pressure zone the “Ridiculously Resilient Ridge” due to its implausible longevity, assuming that it would most likely recede by the subsequent blog post. Instead, the “Triple R” held strong straight through the entire winter—and then recurred, in slightly modified form, throughout the winters of 2014-2015 and 2015-2016.

     

    The multi-year persistence of this anomalous atmospheric ridge was nothing short of extraordinary. The co-occurrence of record low precipitation and record high temperatures associated with the Triple R ultimately yielded California’s most severe multi-year drought on record…..

    Warm West/Cool East” extremes have become more common in recent years

    Our recent work (led by Deepti Singh) answers this question affirmatively: there has indeed been an increase in the number of days each winter characterized by simultaneously very warm temperatures across the American West and very cold temperatures across the East….

    …this increase in contrasting dipole extremes appears to be caused primarily by the increased rate of warming in the western U.S. relative to the eastern U.S…

    Tropical Pacific may offer early warning of “Triple R”-like patterns

    We found that there do indeed appear to be strong relationships between Pacific Ocean temperatures and persistent West Coast ridges conducive to dry conditions in California. Especially prominent are the links to western tropical Pacific Ocean warmth. These connections appear several months in advance, which not only suggests a causal linkage but also hints that it may be possible to predict the occurrence of “Triple R”-like ridges several months in advance….

    What about “The Blob?” Well, we did find a strong statistical linkage between warm ocean conditions in the North Pacific and West Coast ridging—similar to that which occurred during the recent drought. In this case, though, the “chicken or egg” issue rears its head once again: while a time-lagged relationship between autumn ocean temperature and winter ridging did exist in observations, only an contemporaneous relationship existed in climate model simulations….

    Some conclusions, and thoughts about the present winter

    Ocean temperatures have been cool in the eastern tropical Pacific and warm in the western tropical Pacific since early autumn. (NOAA via tropicaltidbits.com)

    Ultimately, we confirm that unusual ocean temperatures are linked to seasonally-persistent West Coast winter ridging similar to the Triple R. Tropical warmth (in the West Pacific) and coolness (in the East Pacific) are both linked to different patterns of North Pacific winter ridging, and may offer an early warning of seasons with an elevated risk of dry conditions in California.

    Interestingly, tropical Pacific Ocean temperatures during autumn 2017 were warm in the west and cool in the east amidst a modest (and ongoing) La Niña event—a combination that suggests a substantially elevated likelihood of West Coast ridging this winter. To date, Southern California has experienced one of its driest starts to the Water Year on record, and strikingly persistent West Coast ridging is now expected to last at least two weeks. It will certainly be interesting to see how this winter plays out in the context of these new research findings.

  5. El Niño Might Speed Up Climate Change

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    • Scientists have evidence that El Niño boosts CO2 levels, and they are pinning down how
    • As a carbon booster, El Niño could hasten rising temperatures, bringing the world to dangerous thresholds sooner than thought. It could also enhance feedbacks between climate and vegetation that could reduce plants’ ability to absorb CO2 in non-Niño years as well. If bad droughts or wildfires kill many trees, for example, forests and their carbon sequestering potential may take centuries to recover, if ever.

    By Tim Vernimmen on December 1, 2017 Read full Scientific American article here

     Every two to seven years, abnormally warm water in the Pacific Ocean causes an atmospheric disturbance called El Niño. It often makes extreme weather worse in various places around the world: greater floods, tougher droughts, more wildfires. Now scientists have new evidence indicating El Niño conditions might also add extra carbon dioxide to the atmosphere as well as lessen the ability of trees to absorb the greenhouse gas…
    ….A recent article in Science about satellite measurements made during El Niño by NASA’s Orbiting Carbon Observatory-2 showed most of the extra CO2 originated in the tropics. It also suggested each tropical region contributed a similar amount of CO2 as in other strong El Niño years, each in its own way. In South America’s Amazon, for example, slower-growing plants absorbed less CO2, whereas in Africa, plants and soils released more of the gas….
  6. Groundwater recharge in the American west under climate change

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    November 16, 2017 University of Arizona  read full ScienceDaily article here

    Groundwater recharge in the Western US will change as the climate warms — the dry southern regions will have less and the northern regions will have more, according to new research. The new study covers the entire US West, from the High Plains states to the Pacific coast, and provides the first detailed look at how groundwater recharge may change as the climate changes. Groundwater is an important source of freshwater, particularly in the West.

    Groundwater…. is often used to make up for the lack of surface water during droughts, the authors note. In many areas of the West, groundwater pumping currently exceeds the amount of groundwater recharge.

    “The portions of the West that are already stretched in terms of water resources — Arizona, New Mexico, the High Plains of Texas, the southern Central Valley — for those places that are already having problems, climate change is going to tighten the screws,” Meixner said….

    R. Niraula, T. Meixner, F. Dominguez, N. Bhattarai, M. Rodell, H. Ajami, D. Gochis, C. Castro. How Might Recharge Change Under Projected Climate Change in the Western U.S.? Geophysical Research Letters, 2017; 44 (20): 10,407 DOI: 10.1002/2017GL075421

  7. Declining baby songbirds need forests to survive drought

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    • Birds in larger mature forest areas, on the other hand, were better able to withstand the dry conditions since these areas offer more shade and resources. Forest cover helps maintain climatic conditions, including moist soil, which is an important factor for wood thrush food availability

    October 19, 2017 Virginia Tech  read full ScienceDaily article here

    According to a new study by biologists at Virginia Tech and the Smithsonian Migratory Bird Center, the offspring of a certain songbird, the wood thrush, are more likely to survive drought in larger forest plots that offer plenty of shade and resources…

    Wood thrush are common to the United States, but populations have declined by more than 60 percent since the 1960s. In addition, many species of songbirds, such as blue jays, robins, and cardinals, as well as wood thrush, face the highest risk of dying within the first five days of leaving their nests.

    …Birds in larger mature forest areas, on the other hand, were better able to withstand the dry conditions since these areas offer more shade and resources. Forest cover helps maintain climatic conditions, including moist soil, which is an important factor for wood thrush food availability. These conditions ultimately make areas more resilient to drought.

    The research highlights the role that forest cover can play in buffering animals from stressful environmental conditions — in this case, promoting survival of young birds during drought conditions,” said Amanda Rodewald, professor and director of conservation science at the Cornell Lab of Ornithology, who was not involved with the research. “This finding is yet another that underscores the importance of maintaining forested landscape mosaics in strategies to conserve biodiversity.”….

    For ideal survival, then, Vernasco says fledglings do well with a “mosaic” of habitats made up of forests that differ in age and thus vegetation structure.

    Ben J. Vernasco, T. Scott Sillett, Peter P. Marra, T. Brandt Ryder. Environmental predictors of nestling condition, postfledging movement, and postfledging survival in a migratory songbird, the Wood Thrush (Hylocichla mustelina). The Auk, 2017; 135 (1): 15 DOI: 10.1642/AUK-17-105.1

  8. ‘Horizontal hurricanes’ – atmospheric rivers pose extreme storm risk but also drought-busting opportunity for California; plans for new 2-3 week forecast and ranking system similar to hurricanes

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    • Severe atmospheric rivers in California could mean 23 days of rain and wind  causing floods and landslides to the tune of $300 billion in property damage per past USGS modeling
    • Atmopheric rivers — while carrying the potential for more damage — will also help California maintain typical rainfall levels amid a drying climate.
    • plan to begin publishing regular 14-day to 21-day outlooks on atmospheric rivers as soon as this winter along with new rating system for intensity on a scale of 1 to 5, similar to hurricanes.

    By Kurtis Alexander September 27, 2017 read full SF Chronicle article here

    …California is facing its own threat of bigger and more destructive storms. Mounting research, much of it done in the wake of the near-record rains that pulled California out of a five-year drought this past winter, shows that seasonal soakers may not come as often as they used to, but could pack more punch when they do arrive.

    ….The massive weather systems that rise out of the Pacific Ocean, now popularly called atmospheric rivers, can drop as much water as Hurricane Irma dumped on Florida this month — billions of gallons that submerged cities and towns.

    …U.S. Geological Survey ran a simulation of what a sequence of severe atmospheric rivers might look like in California…. 23 days of rain and wind that caused floods and landslides to the tune of $300 billion in property damage….big drenchers earlier this year…caused mass flooding in San Jose and other cities and triggered a near-catastrophe at Lake Oroville when a pair of dam spillways failed.

    …A group of Southern California scientists, some of whom are partnering with Sonoma County, plan to begin publishing regular 14-day to 21-day outlooks on atmospheric rivers as soon as this winter. Current forecasts typically don’t anticipate the events more than a week out.

    …Marty Ralph, director of the Center for Western Weather and Water Extremes at UC San Diego’s Scripps Institution of Oceanography, is also working to develop a rating system for the storms.  The blasts will be evaluated for intensity on a scale of 1 to 5, similar to hurricanes. A test run of the ratings last winter pegged the strong atmospheric river in February, which contributed to the damage at Oroville Dam, as a category 5 eventResearch published in the journal Geophysical Research Letters in August, which Ralph participated in, indicates that atmospheric rivers are carrying increasing amounts of water.

    …Sometimes called horizontal hurricanes, atmospheric rivers are exactly what they sound like: airborne channels of water that develop over the Pacific Ocean and are pushed along by strong winds toward the West Coast during the winter….providing as much as 50 percent of the state’s annual rainfall in a matter of days — dumpings that are critical to water supplies but, at times, bring on disaster…

    Another study [published in September] in the journal Scientific Reports, suggests that the swelling intensity of atmospheric rivers — while carrying the potential for more damage — will also help California maintain typical rainfall levels amid a drying climate….

    During the height of the drought, California went as long as a year without seeing a single atmospheric river. But the state was hit by more than 30 of the systems last winter, according to Scripps researchers. That explains why the season was one of the wettest on record….

    Alexander Gershunov, Tamara Shulgina, F. Martin Ralph, David A. Lavers, Jonathan J. Rutz. Assessing the climate-scale variability of atmospheric rivers affecting western North America. Geophysical Research Letters. Volume 44, Issue 15 16 August 2017. Pages 7900–7908 DOI: 10.1002/2017GL074175

  9. Extreme precipitation frequency in CA expected to increase but decrease in other Mediterranean climate regions

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    • Frequencies of extreme precipitation are projected to increase over Northern Hemisphere- especially Califormia- where projected warming is strongest.
    • California’s more nuanced hydrological future reflects a precarious balance between the expanding subtropical high from the south and the south-eastward extending Aleutian low from the north-west– bolstering more extreme precipitation events.
    • More drought expected over Mediterranean basin due to decreased winter precipitation.

    Suraj D. Polade, Alexander Gershunov, Daniel R. Cayan, Michael D. Dettinger & David W. Pierce. Precipitation in a warming world: Assessing projected hydro-climate changes in California and other Mediterranean climate regions. Scientific Reports 7, Article number: 10783 (2017) doi:10.1038/s41598-017-11285-y

    ABSTRACT: In most Mediterranean climate (MedClim) regions around the world, global climate models (GCMs) consistently project drier futures. In California, however, projections of changes in annual precipitation are inconsistent. Analysis of daily precipitation in 30 GCMs reveals patterns in projected hydrometeorology over each of the five MedClm regions globally and helps disentangle their causes. MedClim regions, except California, are expected to dry via decreased frequency of winter precipitation. Frequencies of extreme precipitation, however, are projected to increase over the two MedClim regions of the Northern Hemisphere where projected warming is strongest. The increase in heavy and extreme precipitation is particularly robust over California, where it is only partially offset by projected decreases in low-medium intensity precipitation. Over the Mediterranean Basin, however, losses from decreasing frequency of low-medium-intensity precipitation are projected to dominate gains from intensifying projected extreme precipitation. MedClim regions are projected to become more sub-tropical, i.e. made dryer via pole-ward expanding subtropical subsidence. California’s more nuanced hydrological future reflects a precarious balance between the expanding subtropical high from the south and the south-eastward extending Aleutian low from the north-west. These dynamical mechanisms and thermodynamic moistening of the warming atmosphere result in increased horizontal water vapor transport, bolstering extreme precipitation events.

  10. Has Climate Change Intensified 2017’s Western Wildfires?

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    A firefighter battles the Ponderosa Fire east of Oroville, California, in late August.
    A firefighter battles the Ponderosa Fire east of Oroville, California, in late August. Noah Berger / Reuters

    Robinson Meyer

    This wasn’t supposed to be a bad year for Western wildfires.Last winter, a weak La Niña bloomed across the Pacific. It sent flume after flume of rain to North America and irrigated half the continent. Water penetrated deep into the soil of Western forests, and mammoth snowdrifts stacked up across the Sierra Nevadas. California’s drought ended in the washout.

    Yet fires are now raging across the West. More than two dozen named fires currently burn across Washington and Oregon. More than one million acres have burned in Montana, an area larger than Rhode Island, in the Treasure State’s third-worst fire season on record. And the largest brushfire in the history of Los Angeles currently threatens hundreds of homes in Burbank.

    Canada may be experiencing an even worse year for wildfires: 2.86 million acres have burned in British Columbia, the largest area ever recorded in the province.

    So what happened? How did a wet Western winter lead to a sky-choking summer?

    The answer lies in the summer’s record-breaking heat, say wildfire experts. Days of near-100-degree-Fahrenheit temperatures cooked the Mountain West in early July, and a scorching heat wave lingered over the Pacific Northwest in early August.….

    In other words, the weeks of heat that baked the West in July and August were enough to wipe away some of the fire-dampening effect of the winter storms…

    …“According to climate models, by the end of this century, the western United States is still projected to warm by about another 3.5 degrees Celsius,” he told me. “And when we remember that the relationship between temperature and fire is exponential … we’re really talking about a very different western United States in 50 years.”…