InDialogue with Eelco Rohling and Sean Fleming: Earth’s changing bodies of water

Earth’s bodies of water have gone through considerable changes over time—can these changes tell us anything about climate change—and the future?

Earth’s History and the Oceans

Eelco J. Rohling

Earth’s bodies of water have gone through considerable changes over time—over a lot of time. We have clear geological signs that rivers and lakes have been around for at least 4,400 million years. It never ceases to amaze me that, within 140 million years of its red-hot formation, Earth’s surface had cooled down sufficiently for it to hold fluid water. Then, starting from about 4,000 million years ago, oceans of some shape and form have been around.

Within those ancient bodies of water, life evolved. The earliest signs of life date back to 3,700 million years ago. Then followed a long wait until the first complex life-forms appeared, at around 650 to 700 million years ago. Carbonate coral and shell-reefs became important in shallow waters from about 550 million years ago; many reef systems were formed ever since. And then another major transition took place as late as 125 to 150 million years ago, when carbonate-shelled micro-organisms evolved that rapidly occupied open-ocean surface waters across the world. These organisms are responsible for the formation of geological deposits like the striking white (chalk) cliffs of Dover. Their appearance heralded the start of a fully modern style of operation of the carbon cycle, which includes also atmospheric greenhouse gas concentrations.

Throughout the long history of Earth and its oceans, the carbon cycle and climate changes have been intimately linked. Water is a fantastic substance for absorbing vast quantities of carbon dioxide, and the presence of major bodies of water therefore puts a strong check on greenhouse gas (especially carbon dioxide) concentrations in the atmosphere. Life in the oceans in turn affects the carbon cycle because it involves interaction between dissolved carbon dioxide and both organic matter and carbonate skeletal parts that get (partially) buried and preserved as sediments.

Many ocean sediments eventually get transported into Earth’s hot mantle in subduction zones (think of the Pacific ‘ring of fire,’ where oceanic crust is thrust underneath continental crust). Heating and chemical reactions cause vapour and gas releases, which vent out via volcanoes.  This drives up carbon dioxide levels in the atmosphere and in the oceans. The oceanic part goes directly back into the oceanic carbon cycle. The atmospheric part gets involved in rock weathering on land. This consumes carbon dioxide and releases breakdown products (ions) that flow via rivers back to the oceans, where they help new carbonate formation.

It seems a perfect circle, but it isn’t. There are periods of tiny net carbon dioxide losses or gains. You would not be able to measure these from year to year, but over the multi-million-year timescales of Earth history, they add up to large atmospheric carbon dioxide variations. When this goes up, it gets warmer and weathering increases, which then slowly draws down more carbon dioxide (and vice versa). This way, Earth, with the oceans in a central role, regulates the atmospheric carbon dioxide levels under natural circumstances. It still allows for long, warm periods like the time of the dinosaurs, and excessively cold periods like ice ages or—worse—the exceptional Snowball Earth periods of about 700 million years ago. But overall, the intricately inter-linked long-term carbon cycle processes have held Earth within a ‘habitable’ climate range. Everything changed all the time (and sometimes a lot), but the pace of change was always very slow.

Enter humanity, and our fossil-fuel addiction. We have increased atmospheric carbon dioxide levels in an important manner since the start of the industrial revolution, and especially in the last 60 years. We’re not pushing the actual levels beyond the envelope of where they have been in the natural past—not by a long shot, because we’ve gone from 275 to 410 parts per million, while natural variations have been much greater than that. That’s not the worry. The worry is how fast we’re doing it. We’re doing it easily some 30 to 100 times faster than natural processes have ever done it before (even supervolcanoes cannot get close). Even if all natural removal mechanisms were fired up to 100% their known capacity, then they could offset only about one tenth of our annual emissions.

It is clear, then, that we must drastically reduce our emissions. In addition, it is clear that we must rapidly develop and implement major human-assisted processes of carbon drawdown; that is, we must help nature with the clean-up job. This is important first to deal with ongoing residual emissions that are unavoidable (for example, from cement industry or petrochemical manufacturing), and second to draw down a large part of our past emissions. Both new and existing carbon drawdown approaches are desperately needed at large scales to be able to do this. The sheer amount of carbon removal to be done is enormous.

What can we learn from Ocean and Earth history? That we’re ourselves responsible for the current climate change, and that it’s up to us to deal with it. Mother Nature by itself can and will clean up our greenhouse gases, but don’t wait up for it—it will take her several hundred thousands of years even when working flat-out. We urgently need to lend her a helping hand if we want improvement on societally relevant timescales. Doing so will, incidentally, be a major driver for innovation, development, job creation, and growth potential. What an opportunity!

Eelco J. Rohling is author of The Oceans. He is professor of ocean and climate change in the Research School of Earth Sciences at the Australian National University and at the University of Southampton’s National Oceanography Centre Southampton.

 

Global Warming and our Rivers

Sean W. Fleming

A common misconception about climate change and its impacts on environmental and social systems, like our rivers and water resources, is that it’s something that will only happen at some point in the future.  In reality, climate change is happening now.  Not only does climate vary both naturally due to processes like El Niño, and in response to local-scale human activities like urban heat islands, but global anthropogenic greenhouse gas warming has also been going on for generations – and these signals can be directly detected in actual observational datasets! 

FlemingIn fact, doing so is a crucially important part of understanding the reality and broader impacts of climate change.  When people talk about climate change, they often talk about climate models: math and software that simulate the global climate system.  And because climate models are exactly that – detailed representations of climate, but not of everything climate affects – to understand the impacts on water resources, the predictions of those climate models are taken by hydrologists and other scientists and engineers and run through still other models, such as simulations of watershed hydrology, water quality, habitat quantity and quality, or reservoir operations.  All these models are amazing technical feats, and they’re fantastic for isolating the impacts of human-caused global climate change from other sources of environmental variability.  But by necessity, they contain a lot of simplifications.  Rivers are immensely complex systems that integrate the effects of just about everything in their watersheds, from weather and climate, to forests and icefields, to land use changes like forestry and urban sprawl.  It turns out they’re also full of unexpected surprises. 

So, while the physics-based virtual realities of process simulation models are great tests of what we know about the world and are our best bet for making predictions based on that knowledge, they can only contain what we know, not what we don’t know.  In contrast, drawing sophisticated data analytics algorithms from statistics, digital signal processing, information theory, and artificial intelligence, and applying them to actual measurements of climate and the things it affects, provides a valuable “ground truth” – giving direct empirical evidence for the impacts of climate change on rivers, and often revealing previously unknown patterns that the next generation of models must then seek to explain and, ultimately, predict.

My favorite example is how mountain glaciers control water resource responses to climate change.  My doctoral studies began in 2001 with a glacier science expedition to the high peaks of the Yukon-Alaska-British Columbia border region.  Hearing summer melt water run deep in the crevasses of Trapridge Glacier and watching white-water streams gushing from its terminus, I decided to focus my research on statistical and machine learning studies of decades-long historical streamflow data in glacial watersheds.  The goal was to understand how these gigantic ice cubes modify the downstream expressions of climate change – specifically, by comparing climate variability and change responses in several glacier-fed rivers to a control population of nearby rivers that didn’t have glaciers in their headwaters. 

We made a few discoveries.  One revelation was that recent global warming affected the net downstream flow of glacial rivers in a completely different way from non-glacial watersheds: glacial rivers grew larger while non-glacial rivers shrank.   It was solid evidence of the present reality of climate change, but at the same time, specific patterns like this were poorly represented, if at all, in environmental models.  With further refinement by many scientists worldwide, this knowledge has since become part of a standard model of how water resources downstream of mountain glaciers – which lie at the heart of the continental “water towers” of the Rockies, Andes, Alps, and Himalayas, in turn feeding the headwaters of the Columbia, Amazon, Danube, Brahmaputra, and Yangtze rivers, among others – are affected by climate change.

Sean W. Fleming is author of Where the River Flows. He has two decades of experience in the private, public, and nonprofit sectors in the United States, Canada, England, and Mexico, ranging from oil exploration to operational river forecasting to glacier science. He holds faculty positions in the geophysical sciences at the University of British Columbia and Oregon State University.

Sean Fleming: The Necessity of Water

Changes across the globe are placing unprecedented pressure on our water resources. Today, according to a United Nations report, more than one billion people do not have access to clean water, and 1.4 billion live in river basins where water use exceeds recharge rates. Another two billion or so water users will be added to the world’s population by midcentury. This population growth, together with expansion of agricultural and industrial production as poorer nations develop, is expected to increase global water demand by a stunning 55% by 2050.

Not only do these factors increase water demand, they also signify greater global exposure to water-related hazards, including pollution and flood risk, as more people settle on floodplains, for instance, and more municipal, industrial, and agricultural effluent is discharged into the environment. At the same time, there is a strong scientific consensus that the net increase in atmospheric greenhouse gas concentrations is large enough to detectably alter global climate. This can be attributed to activities like massive fossil fuel combustion, industrial livestock production, and widespread deforestation. Current projections suggest that the main hydrological effect for most basins will be to amplify the water cycle, which may increase runoff in many regions but reduce supplies in others. More importantly, it may widely increase the intensity of both the yearly rainy and dry seasons, further increasing flood and drought risks. And river channelization, damming, contamination, and upstream water withdrawals have so degraded aquatic habitat that many freshwater biological populations have collapsed, some species have been entirely extirpated from parts of their home ranges, and others are at risk of extinction altogether. We are facing a dark constellation of regional water resource disasters, growing and coalescing into what appears to be an emerging global catastrophe of human welfare and the environment.

To mitigate the impacts of these changes, we need to invest deeply in a coordinated, broad-based, and large-scale drive to create new science and technology that addresses the needs and aspirations of the current and future global populations in a healthy and sustainable way. Only time will tell which specific directions these innovations will take, but there are a few obvious paths. This includes:

  • Lower-energy, lower-cost, and cleaner desalinization technologies to sustainably extract fresh water from deep aquifers and the ocean
  • Further technology- and policy-driven improvements in the efficiency of water use and, in particular, water distribution systems
  • Public health steps to curb population growth in ways that are new and ambitious, yet fully respectful of individual rights and freedoms
  • And perhaps most importantly of all, improved environmental monitoring and prediction technologies, so we know what’s happening with our water resources today and what to plan for in the future.

There is justification for having faith that we can get real traction on water scarcity. The development of more water-efficient technologies for homes, farms, and factories is an obvious example. Indeed, water use in the United States has leveled off near 1970 rates in spite of both population and economic growth. Granted, unsustainable water practices during regional droughts, such as groundwater mining in California, revealed a chink in the armor. Furthermore, stabilization of water demand seems restricted, at best, to a handful of rich nations. Nevertheless, the overall statistic must be acknowledged as the stunning success, cause for optimism, and clear template for emulation that it is—a shining citadel on the hill, as it were.

Improvements in water quality are another example. Admittedly, over much of the world, rapid agricultural and industrial expansion are making water quality worse, not better. Shortages of potable water due to fecal contamination remains a huge issue globally; in fact, another UN report indicates that inadequate access to clean water kills more people through the associated disease alone than are killed by guns in war. And emerging contaminants, like pharmaceuticals and plastic breakdown products, are an increasingly worrisome threat. Yet improved awareness, legislation, and technology have yielded tremendous gains. The days of rivers ablaze— this happened to the Cuyahoga River in Ohio, which was so polluted with flammable contaminants that in 1969 it actually caught fire—seem to be over. Overall, water quality across the industrialized regions of the developed world is largely much better now than it was, say, forty or fifty years ago.

Another broad reason for optimism is the seeming paradox of water conflict. Ismail Serageldin, a former World Bank vice president, famously warned that the wars of the twenty-first century will be fought over water. It turns out, though, that water resource conflict and cooperation are surprisingly nuanced. While squabbles abound, actual shooting wars solely over water, even in regions that are both arid and troubled, are virtually nonexistent. And cooperation might be at least as common as conflict.

But with exploding global demand, this all might change.

As water resource pressures mount, our efforts to manage these changes must grow commensurately. And at the heart of these efforts must be good hydrologic science, because without that, everything else will merely be a shot in the dark. Advances are required in two directions. First and foremost is improved ability to monitor water, and associated variables like land use and climate. This will be accomplished by growing our networks of ground observation stations, and by expanding the scope, accessibility, and accuracy of airborne and satellite remote sensing data. The second is to further develop our mathematical modeling and prediction technologies for watershed systems. Data analytics, statistical and machine learning-based prediction, and physical process simulation techniques – rivers in silicon, as it were – are how we test our understanding of watersheds and transform observational data and theoretical knowledge into a scientifically defensible and socially responsible basis for informed predictions and sound advice.

Water isn’t optional. Water is necessary for our very existence, for our continued economic development, and for the health of the web of life that supports us. It’s also limited in its availability, and there are no substitutes for it. Whatever path humanity chooses to follow, it will be up to hydrologists to present society with the options available, and the corresponding pros and cons, for the management of our water resources. And to do that, water resource scientists and engineers need to understand watershed systems in detail, and to accurately, precisely, consistently, and quantitatively predict the impacts on those systems from both natural phenomena and human interventions. Viewed from this perspective, it is perhaps not too dramatic to assert that the future of the world will depend, in a small but real way, on a quantum leap forward in our understanding of the physics of rivers.

Sean W. Fleming has two decades of experience in the private, public, and nonprofit sectors in the United States, Canada, England, and Mexico, ranging from oil exploration to operational river forecasting to glacier science. He holds faculty positions in the geophysical sciences at the University of British Columbia and Oregon State University.

Sean Fleming: The Water Year in Review

The top five water-related news stories of 2017—and what to expect for 2018

FlemingThe thing about water is that something’s always happening, and the implications of that fact are growing – fast.  What are the top five water-related news stories of 2017?  Read on to see, along with a little context and some implications for next year and beyond.

Oops!  (The Oroville Dam evacuation)

Possibly the most obvious water story of 2017 happened right after the New Year: nearly 200,000 Californians were evacuated beneath Oroville Dam as it threatened to fail under record flooding, which in turn ended a historic drought that had cost the state billions of dollars.  Previously of little note to most living outside the region, Oroville is in fact the tallest dam in the US.  It’s located on the Feather River, a headwater basin to the Sacramento River that drains the western slopes of the snow-laden Sierra Nevada and Cascades in the wet, northern part of California.  Oroville Dam is a key component the California State Water Project, shifting water into the California Aqueduct to help irrigate the Central Valley, which produces about 25% of the food consumed in the US, and to transport water to southern Californian urban centers.  Critics charge that in spite of its size and status as a cornerstone of the civil works in a heavily populated but largely arid state where water is everything, dam maintenance and upgrading lagged far behind, setting the stage for problems.  Record rains in February provided the trigger, and the main spillway failed – which might in turn have undermined the dam as a whole, sending the entirety of massive Lake Oroville downstream all at once in a wave of destruction and death.  Disaster was averted, but the costs were tremendous and the risks were real.  For thoughts on improving America’s river infrastructure, see my recent Scientific American post.

Water goes bang on the India-China border

The most exciting, yet perhaps most under-reported water story of 2017 took place on the India-China border.  A military buildup and tense standoff over disputed ownership of a Himalayan frontier area shared by China, Nepal, Bhutan, and India this summer may have cooled off, but India charges that China followed up by using water as a weapon – withholding key data that India needs to manage lethal monsoon flooding on transboundary rivers.  Violent international conflict solely over water is extremely rare because it usually doesn’t work strategically, though it does happen from time to time.  For instance, in 1965, when Syria was building an upstream diversion of a tributary to the River Jordan that would deeply reduce Israel’s water supply – a catastrophe for a desert nation – Israel responded with air strikes against the facility.  And water has been used as a weapon in wars that were being fought for other reasons: Chiang Kai-shek’s Nationalist government in China opened the dikes on the Yellow River in 1938 in an effort to hold back the invading Imperial Japanese army. The action was only partially successful and had a disastrous humanitarian cost.  The soaring mountain ranges wrapping around the Tibetan Plateau – including the Hindu Kush, Karakoram, and Himalayas, spanning China, India, Pakistan, and  several other countries – host one of the world’s largest remaining icefields and are the source of the Indus, Yangtze, Yellow, Ganges, Brahmaputra, and Mekong Rivers among others, and thus help provide water to a full quarter of the global human population.  Perhaps nowhere else on Earth is it more important for nations to cooperate over water.

Two inter-state water lawsuits go to the US Supreme Court

The volume was turned up in the country’s water wars, with SCOTUS announcing this fall it will hear both Texas’s lawsuit against New Mexico over Rio Grande water rights, and Florida’s lawsuit against Georgia over the Apalachicola.  Rivers and aquifers don’t respect borders.  The geophysics of where water comes from and how and where it flows is complex, fascinating, and full of surprises, such as flash floods, alternating drought and flood sequences, and abrupt and catastrophic changes in river channel location.  And those are just the natural aspects – the engineering and management part can be just as complicated for some basins, and a high ratio of demand to supply, as we have in the increasingly heavily populated deserts of the Southwest for instance, exacerbates these issues.  Originating from snowy headwaters in the mountains of southern Colorado and northern New Mexico, the Rio Grande flows south through increasingly arid country and then turns southeastward, forming the US-Mexico border until emptying in the Gulf of Mexico.  Water projects abound on the Rio Grande, and each influences the other in some way.  For example, the San Juan-Chama project diverts water from the Colorado River into the Rio Grande, municipal groundwater pumping in Albuquerque interacts with Rio Grande flows through subterranean geologic pathways, and a series of dams withdraws water from the river for agriculture, reducing what’s left for downstream users.  Water law is complicated.  Texas says New Mexico is taking more than its fair share of Rio Grande water; New Mexico says it isn’t.  The potential for disagreement over water will only continue to grow in the Southwest, though there are success stories as well: after some earlier missteps, Las Vegas has invented one of the most advanced and successful water conservation programs around, reportedly reducing its water consumption by almost a quarter over a ten-year period while its population grew by half a million.

Saying goodbye to the Paris Agreement on climate change

Why is climate change important to rivers?  Lots of natural processes and human activities affect how high rivers run and how much water arrives at your tap, and climate variables like precipitation and temperature rank high among these influences.  While the new administration’s withdrawal from the Paris Agreement in 2017 was obviously a setback for action on climate change, it was also a democratic response to widespread sentiment.  And this fact suggests that explaining climate change may be turning into the greatest science communication failure in history.  As scientists, we clearly need to adjust course – but in what direction?  Consider a recent article by a multi-disciplinary team in the respected research journal, Global Environmental Change.  Applying complex network theory (kind of a mathematical formalization of the seven degrees of Kevin Bacon) to social media feeds about climate change, they demonstrated the dominance of so-called echo chambers, and that constructive progress is made only when groups with opposing views actually talk with each other.  Consider also that populism – which is by nature skeptical around the competence and integrity of designated experts – has been growing over the last decade on both the left and right, as evidenced by the mayoralties of Rob Ford in Toronto and Boris Johnson in London, the Tea Party and Occupy movements, Brexit, and Bernie and The Donald.  If there is a silver lining to withdrawal from the Paris accords, it’s that it may teach us valuable lessons around communicating about climate change: reach out to people who don’t believe us yet, treat them with respect, and focus on just explaining our science.

Houston, we have a problem

Hurricane Harvey hit Houston hard.  In late August, the fourth largest city in the US, with over 4 million residents counting Harris County, was at the epicenter of what some are saying will be the costliest natural disaster in US history.  Though no hurricane is to be trifled with, why was the flooding so intense in this case?  To be sure, the rainfall generated by this particular storm was unusually heavy.  But risk is, by definition, what you get when you take the probability that something bad will happen (like record rainfall under a hurricane) and multiply it by the impact it will have if it does happen (like flooding and the associated economic cost and human suffering).  In the case of Harvey’s visit to Houston, it had a lot to do with local-scale choices that affected the second part of that equation.  In fact, parts of the greater Houston metropolitan area have seen a spate of floods over the last few years, and they weren’t all associated with huge storms.  The region has experienced an explosion of population growth and urban sprawl.  Lots of residences were built in low-lying, flood-prone areas, which is the single best of way of increasing flood risk.  And urbanization – the conversion of wild or agricultural land to rooftops, parking lots, and roadways – is another powerful flood risk factor.  Soils and wetlands hold on to rainwater for a while, and then gently release it to natural drainage systems like aquifers and rivers.  If you pave and build over these things, their ability to attenuate flooding is removed.  While these effects are particularly noticeable in Houston, and especially so when the city gets hit by a major hurricane, they’re ubiquitous; increased flooding in the UK over the last decade has been attributed to exactly the same causes.

What will 2018 have in store for us?  If we can be sure about one thing, it’s to expect the unexpected.  But the larger trends are clear.  Global water demand will increase 55% in the next few decades, urbanization will spread, tens of millions more will congregate in floodplain-located megacities, the climate will subtly but profoundly shift overhead, and cooperation and conflict over water will vie for supremacy.  We can, in short, expect that water stories will make the news with increasing frequency and force.

Sean W. Fleming has two decades of experience in the private, public, and nonprofit sectors in the United States, Canada, England, and Mexico, ranging from oil exploration to operational river forecasting to glacier science. He holds faculty positions in the geophysical sciences at the University of British Columbia and Oregon State University. He is the author of Where the River Flows: Scientific Reflections on Earth’s Waterways.