Stories tagged sea level rise

Apr
04
2011

We often hear about gravity being different on other planets--the Moon is an oft-cited example of how weaker gravity makes you weigh less. But did you know that gravity actually varies on our own planet?

There's this thing called a geoid. It sounds like something out of a sci-fi story, but it's quite real. The geoid is a map of the Earth's gravitational field. And since gravity impacts things like sea level and currents, it's important to understand how it varies.
Welcome home: I think that's South America on the left there...
Welcome home: I think that's South America on the left there...Courtesy ESA/HPF/DLR

Luckily, those crafty Europeans came up with the GOCE (Gravity field and steady-state Ocean Circulation Explorer) satellite, which has painted the clearest picture yet of the geoid. With its variations exaggerated, it makes the Earth look like a giant potato. The variations come from unevenness in earth's mass and shape. Its wobbly surface represents what shape the oceans would take without current, wind, or tide to move them. The satellite also studies ocean circulation and the movement of ice.

This information is particularly important to understanding sea level rise. Scientists predict that, on average, sea level will rise 3 feet overall by 2100. But those three feet will be distributed differently throughout the world, and studying that distribution is pretty complicated. There's the impact of the geoid and of gravity from large ice sheets, but winds and water circulation, water temperature, salinity, meltwater from ice sheets, rainwater runoff, and land changes all leave their marks.
Home sweet tuber: Aww
Home sweet tuber: AwwCourtesy Lumbar

Some of these changes redistribute water (ex. geoid), others add to the volume of seawater (ex. temperature increases), and still others modify the land's height relative to the water (ex. land changes, such as sedimentation and oil extraction). Some changes leave a lasting impact (ex. meltwater from glaciers), while others can vary by the hour or the season (winds).

By developing this most-accurate-to-date geoid and ocean circulation model, researchers have created a picture of sea level at its natural state and modeled some of the processes that alter that state, so that we have a reference point for understanding many of the less-defined factors in sea level rise. And that, my friends, will help us better anticipate and plan for the changes ahead.

Plus it's just kinda cool to see how the Earth is really shaped, huh?

Feb
14
2011

We've probably been debating the virtues of urban areas since humans gathered in the first cities thousands of years ago. But one question we probably haven't explored much is how we can prepare our cities for climate change.

Climate and sea level have changed slowly throughout humanity's history, and we've been able to adapt. Until quite recently, humans either didn't build settlements in risky areas, or the ones they built (say on floodplains or near a sea shore) were temporary and easily moved or abandoned.

Now that we face accelerating and more extreme changes in the next 100 years, we also have some very permanent structures (and infrastructures) in the riskiest of places. Over 100 million people live in areas likely to be underwater by 2100. And even landlubbers face the challenges of more frequent extreme weather events--heavier rainfalls, droughts, etc.

St. Paul, MN: I bet there are thousands of ideas brewing in these buildings every day (especially the one on the lower left side).
St. Paul, MN: I bet there are thousands of ideas brewing in these buildings every day (especially the one on the lower left side).Courtesy John Polo

Luckily, engineers are already beginning to plan for these changes as they retrofit and build new buildings and infrastructure. Often, these engineers are ahead of city building codes and have trouble persuading property owners to invest in addressing threats that lie in the future. But isn't it better safe than sorry? Maybe we could build cities so strong that climate change barely bothers us.

And even luckier perhaps is that cities are hotbeds of innovation and creativity. We could see the efforts of these engineers as just another example of urban virtues. More people mean more ideas and more resources devoted to the cause. And in our rapidly changing world, we need that teamwork more than ever.

According to a recent study, the rate of groundwater depletion more than doubled since 1960. Groundwater provides most of the water we use in our homes and fields, including drinking water. It's estimated that groundwater depletion accounts for about 25 percent of sea level rise each year because most of the removed water evaporates and falls into the ocean. To compound matters, hard surfaces such as concrete prevent rainwater from replenishing underground reservoirs and aquifers.

About 70 percent of the world's freshwater is frozen in land-based ice sheets and glaciers, which are also melting into the ocean. So, cisterns? Desalination plants? How do you think we'll get freshwater when the frozen stuff is all that's left?

Jul
14
2010

"Here's what I've lately decided: I'm the little kid in "The Sixth Sense" who sees the dead people. I'm getting really sick of being this Cassandra. I mean, it's kind of miserable."
Peter Ward, Author of "The Flooded Earth"

Salon.com recently interviewed Peter Ward about the future of American cities as sea levels rise. The interview was not just depressing--some of Ward's comments were downright terrifying. Regarding the possibility of ending ocean currents, he commented that with one exception, every past mass extinction was caused by volcanic global warming events. He notes:

"Ocean currents slow down. You lose your wind, everything…. Everything goes stagnant, and a stagnant ocean becomes an oxygen-free ocean, and an oxygen-free ocean breeds very bad microbes."

But perhaps the most disturbing implication in the interview was that in order to be heard, scientists have to weaken their own arguments, which in turn weakens governmental response and public perception of the danger.

"No one wants to be branded as some sort of flaming political agenda-ist. These estimates aren't going down, because the amount of CO2 going into the atmosphere keeps going up. And in fact we keep shooting over the worst level projections that people were saying two or three years ago."

So what can we do? This kind of catastrophic discussion makes my weekly reusable bag use at Rainbow seem like chewing gum in a leaking dam, or maybe that first cap BP put on the well. It may make a tiny difference, but it won't avoid disaster.

After all the reading I've done the last few weeks about climate change, I've begun to think the first step is confronting the evidence as a nation (good luck, right?). The hardest part then is identifying and committing to mitigation/response plans--I say that because we are already deeply impacting our environment in ways that we can't reverse. But I also think that as Ward says, "…wherever there's challenges, there are opportunities." If we're going to make changes on a broad scale, we have to find a way to be optimistic about these very depressing facts.

In preparation for the Future Earth exhibit (more soon!), we've been working with the Center for Coastal Margin Observation and Prediction (CMOP). You can read more about their research and outreach efforts on Science Buzz or on their website. The tagline on their website, "Understanding variability to anticipate change," is just the kind of proactive attitude we need as we face rising sea levels.

"I have a fundamental belief that science and education are essential to prepare our society to anticipate and steer changes."
Antonio Baptista, CMOP Director

Where do you find hope for our future? Please reply in the comments!