Science Current Events | Science News | Brightsurf.com
 

Rising oceans -- too late to turn the tide?

July 18, 2011

Melting ice sheets contributed much more to rising sea levels than thermal expansion of warming ocean waters during the Last Interglacial Period, a UA-led team of researchers has found

Thermal expansion of seawater contributed only slightly to rising sea levels compared to melting ice sheets during the Last Interglacial Period, a University of Arizona-led team of researchers has found.

The study combined paleoclimate records with computer simulations of atmosphere-ocean interactions and the team's co-authored paper is accepted for publication in Geophysical Research Letters.

As the world's climate becomes warmer due to increased greenhouse gases in the atmosphere, sea levels are expected to rise by up to three feet by the end of this century.

But the question remains: How much of that will be due to ice sheets melting as opposed to the oceans' 332 billion cubic miles of water increasing in volume as they warm up?

For the study, UA team members analyzed paleoceanic records of global distribution of sea surface temperatures of the warmest 5,000-year period during the Last Interglacial, a warm period that lasted from 130,000 to 120,000 years ago.

The researchers then compared the data to results of computer-based climate models simulating ocean temperatures during a 200-year snapshot as if taken 125,000 years ago and calculating the contributions from thermal expansion of sea water.

The team found that thermal expansion could have contributed no more than 40 centimeters - less than 1.5 feet - to the rising sea levels during that time, which exceeded today's level up to eight meters or 26 feet.

At the same time, the paleoclimate data revealed average ocean temperatures that were only about 0.7 degrees Celsius, or 1.3 degrees Fahrenheit, above those of today.

"This means that even small amounts of warming may have committed us to more ice sheet melting than we previously thought. The temperature during that time of high sea levels wasn't that much warmer than it is today," said Nicholas McKay, a doctoral student at the UA's department of geosciences and the paper's lead author.

McKay pointed out that even if ocean levels rose to similar heights as during the Last Interglacial, they would do so at a rate of up to three feet per century.

"Even though the oceans are absorbing a good deal of the total global warming, the atmosphere is warming faster than the oceans," McKay added. "Moreover, ocean warming is lagging behind the warming of the atmosphere. The melting of large polar ice sheets lags even farther behind."

"As a result, even if we stopped greenhouse gas emissions right now, the Earth would keep warming, the oceans would keep warming, the ice sheets would keep shrinking, and sea levels would keep rising for a long time," he explained.

They are absorbing most of that heat, but they lag behind. Especially the large ice sheets are not in equilibrium with global climate," McKay added. "

Jonathan Overpeck, co-director of the UA's Institute of the Environment and a professor with joint appointments in the department of geosciences and atmospheric sciences, said: "This study marks the strongest case yet made that humans - by warming the atmosphere and oceans - are pushing the Earth's climate toward the threshold where we will likely be committed to four to six or even more meters of sea level rise in coming centuries."

Overpeck, who is McKay's doctoral advisor and a co-author of the study, added: "Unless we dramatically curb global warming, we are in for centuries of sea level rise at a rate of up to three feet per century, with the bulk of the water coming from the melting of the great polar ice sheets - both the Greenland and Antarctic Ice Sheets."

According to the authors, the new results imply that 4.1 to 5.8 meters, or 13.5 to 19 feet, of sea level rise during the Last Interglacial period was derived from the Antarctic Ice Sheet, "reemphasizing the concern that both the Antarctic and Greenland Ice Sheets may be more sensitive to warming temperatures than widely thought."

"The central question we asked was, 'What are the warmest 5,000 years we can find for all these records, and what was the corresponding sea level rise during that time?'" McKay said.

Evidence for elevated sea levels is scattered all around the globe, he added. On Barbados and the Bahamas, for example, notches cut by waves into the rock six or more meters above the present shoreline have been dated to being 125,000 years old.

"Based on previous studies, we know that the sea level during the Last Interglacial was up to 8.5 meters higher than today," McKay explained.

"We already knew that the vast majority came from the melting of the large ice sheets in Greenland and Antarctica, but how much could the expansion of seawater have added to that?"

Given that sea surface temperatures were about 0.7 degrees warmer than today, the team calculated that even if the warmer temperatures reached all the way down to 2,000 meters depth - more than 6,500 feet, which is highly unlikely - expansion would have accounted for no more than 40 centimeters, less than a foot and a half.

"That means almost all of the substantial sea level rise in the Last Interglacial must have come from the large ice sheets, with only a small contribution from melted mountain glaciers and small ice caps," McKay said.

According to co-author Bette Otto-Bliesner, senior scientist at the National Center for Atmospheric Research (NCAR) in Boulder, Colo., getting the same estimate of the role ocean expansion played on sea level rise increases confidence in the data and the climate models.

"The models allow us to attribute changes we observe in the paleoclimate record to the physical mechanisms that caused those changes," Otto-Bliesner said. "This helps tremendously in being able to distinguish mere correlations from cause-and-effect relationships."

The authors cautioned that past evidence is not a prediction of the future, mostly because global temperatures during the Last Interglacial were driven by changes in the Earth's orbit around the sun. However, current global warming is driven by increasing greenhouse gas concentrations.

The seasonal differences between the northern and the southern hemispheres were more pronounced during the Last Interglacial than they will be in the future.

"We expect something quite different for the future because we're not changing things seasonally, we're warming the globe in all seasons," McKay said.

"The question is, when we think about warming on a global scale and contemplate letting the climate system change to a new warmer state, what would we expect for the ice sheets and sea levels based on the paleoclimate record? The Last Interglacial is the most recent time when sea levels were much higher and it's a time for which we have lots of data," McKay added.

"The message is that the last time glaciers and ice sheets melted, sea levels rose by more than eight meters. Much of the world's population lives relatively close to sea level. This is going to have huge impacts, especially on poor countries," he added.

"If you live a meter above sea level, it's irrelevant what causes the rise. Whether sea levels are rising for natural reasons or for anthropogenic reasons, you're still going to be under water sooner or later."

###

Reference:

McKay, N., J. T. Overpeck, and B. Otto-Bliesner (2011). The role of ocean thermal expansion in Last Interglacial sea level rise. Geophys. Res. Lett., doi:10.1029/2011GL048280, in press. A version of the accepted paper is available online at the Geophysical Research Letters site: http://www.agu.org/journals/gl/papersinpress.shtml

University of Arizona


Related Sea Level Current Events and Sea Level News Articles


Early use of 'hurricane hunter' data improves hurricane intensity predictions
Data collected via airplane when a hurricane is developing can improve hurricane intensity predictions by up to 15 percent, according to Penn State researchers who have been working with the National Oceanic and Atmospheric Administration and the National Hurricane Center to put the new technique into practice.

Will more snow over Antarctica offset rising seas? Don't count on it
Many factors related to warming will conspire to raise the planet's oceans over coming decades -- thermal expansion of the world's oceans, melting of snow and ice worldwide, and the collapse of massive ice sheets.

Scientists predict extensive ice loss from huge Antarctic glacier
Current rates of climate change could trigger instability in a major Antarctic glacier, ultimately leading to more than 2m of sea-level rise.

Evidence of repeated rapid retreat of the East Antarctic ice sheet
Research published in the journal Nature on May 19, 2016 has revealed that vast regions of the Totten Glacier in East Antarctica are fundamentally unstable and have contributed significantly to rising sea levels several times in the past.

New evidence that humans settled in southeastern US far earlier than previously believed
The discovery of stone tools found in a Florida river show that humans settled the southeastern United States far earlier than previously believed--perhaps by as much as 1,500 years, according to a team of scientists that includes a University of Michigan paleontologist.

Scientists track Greenland's ice melt with seismic waves
Researchers from MIT, Princeton University, and elsewhere have developed a new technique to monitor the seasonal changes in Greenland's ice sheet, using seismic vibrations generated by crashing ocean waves.

How much does groundwater contribute to sea level rise?
Groundwater extraction and other land water contribute about three times less to sea level rise than previous estimates, according to a new study published in the journal Nature Climate Change.

Microbes make tubular microtunnels on earth and perhaps on mars
Tubular microtunnels believed to be the trace fossils formed by microbes inhabiting volcanic rock interiors have only been reported in oceanic and subglacial settings.

What lies beneath West Antarctica?
Three recent publications by early career researchers at three different institutions across the country provide the first look into the biogeochemistry, geophysics and geology of Subglacial Lake Whillans, which lies 800 meters (2,600 feet) beneath the West Antarctic Ice Sheet.

Reducing food waste could help mitigate climate change
About a tenth of overall global greenhouse-gas emissions from agriculture could be traced back to food waste by mid-century, a new study shows. A team from the Potsdam Institute for Climate Impact Research for the first time provides comprehensive food loss projections for countries around the world while also calculating the associated emissions.
More Sea Level Current Events and Sea Level News Articles

Sea Level

Sea Level
by Sea Level (Author)


Track: 1. Rain In Spain 6:47 2. Shake A Leg 3:53 3. Tidal Wave 5:40 4. Country Fool 3:40 5. Nothing Matters But The Fever 7:20 6. Grand Larceny 5:23 7. Scarborough Fair 5:31 8. Just A Good Feeling 3:01

Life at Sea Level

Life at Sea Level
by Seaworthy Publications, Inc.


Life at Sea Level is the latest work of one of America’s finest travel guide authors. For nearly 20 years, Stephen J Pavlidis has been writing books about the Bahamas and the Caribbean islands. He has written 14 guides covering virtually all the geography from south Florida to Trinidad and Tobago, including
many lesser known destinations such as Guatemala and Honduras. That writing was done aboard his 40-foot sailboat, making careful notes, tedious maps and talking to the locals he met ashore.

Most of Steve’s books report facts about the regions and islands he visited. Finally, in Life at Sea Level he tells some of the other stories of the very real things that happened during his island time and of the very real people he knew or historically researched. He tells...

High Tide On Main Street: Rising Sea Level and the Coming Coastal Crisis

High Tide On Main Street: Rising Sea Level and the Coming Coastal Crisis
by John Englander (Author)


NEW 2nd Edition (10-16-13) of best selling book that described a superstorm hitting Atlantic City and New York City -- exactly one week before Sandy. Just one of dozens of scenarios in this amazing book. Find out the other forecasts. Rave reviews from experts and Amazon readers. Fully updated and revised. New Introduction by Governor Christine Todd Whitman. For 6,000 years sea level has changed little. Now it it has started rising again, moving the shoreline too. In clear, easy-to-understand language, this book explains: * The science behind sea level rise, plus the myths and partial truths used to confuse the issue. * The surprising forces that will cause sea level to rise for 1,000 years, as well as the possibility of catastrophic rise this century. * Why the devastating economic...

Scholastic Reader Level 1: The Sea Monster: A Steve and Wessley Reader

Scholastic Reader Level 1: The Sea Monster: A Steve and Wessley Reader
by Jennifer E. Morris (Author)


Steve and Wessley are back in the hilarious follow-up to THE ICE CREAM SHOP!

There is something in the pond. Wessley thinks it's just a stick. But Steve thinks it may be something much scarier....

Readers will love the second outing of hilarious duo Steve and Wessley, two friends who always seem to get into the silliest situations!

The Sea

The Sea
by John Banville (Author)


In this luminous new novel about love, loss, and the unpredictable power of memory, John Banville introduces us to Max Morden, a middle-aged Irishman who has gone back to the seaside town where he spent his summer holidays as a child to cope with the recent loss of his wife. It is also a return to the place where he met the Graces, the well-heeled family with whom he experienced the strange suddenness of both love and death for the first time. What Max comes to understand about the past, and about its indelible effects on him, is at the center of this elegiac, gorgeously written novel — among the finest we have had from this masterful writer.

DK Readers L1: Sea Otters (DK Readers: Level 1)

DK Readers L1: Sea Otters (DK Readers: Level 1)
by DK (Author)


Get a close-up look at the lives of sea otters and watch them eat, play, groom, and dive together. Filled with bold, adorable images of these aquatic creatures in their natural habitat, Sea Otters explores a day in the life of these furry, whiskered marine mammals.Perfect for 3–5 year olds learning to read, Level 1 titles contain short, simple sentences with an emphasis on frequently used words. Stunning photographic images with labels provide visual clues to introduce and reinforce vocabulary.Lexile measure: 410
Fountas and Pinnell Text Level Gradient: ITrusted by parents, teachers, and librarians, and loved by kids, DK's leveled reading series is now revised and updated. With shiny new jackets and brand new nonfiction narrative content on the topics kids love, each book is written...

Twenty Thousand Leagues Under Sea, Level 1, Penguin Readers (2nd Edition) (Penguin Readers: Level 1)

Twenty Thousand Leagues Under Sea, Level 1, Penguin Readers (2nd Edition) (Penguin Readers: Level 1)
by Jules Verne (Author)


Classic / British English This is the story of Captain Nemo and his submarine, the Nautilus. One day, Nemo finds three men in the sea. For months the men live on the Nautilus. They find a town on the sea floor, beautiful coasts and a lot of gold. But they want to go home. Can they escape from Nemo's submarine?

Sea Level

Sea Level
by Nancy Kilgore (Author)


Brigid Peterson is the new minister in the remote seaside town of Sand Hill.  The year is 1980 and her parishioners are wary and even hostile to a woman in the pulpit.  She finds a kindred spirit in her new friend Mary Bradley, an artist who believes in the goddess.  But Mary has fallen hopelessly in love with a local drifter, and Brigid's marriage is beginning to crumble, and when Brigid preaches about the female side of God, the whole town divides over her.  Both women have to dive deeper into their spiritual life to find the way through.

Sea Level is a story about ordinary small town life, the mystical landscape of the Delmarva Peninsula, and the passions that erupt over conflicts of belief.

Last Psalm at Sea Level

Last Psalm at Sea Level
by Meg Day (Author)


Poetry. LGBT Studies. "Lovely does not suffice, nor does lyric. Eloquence is only a grasping in the space of ineffable air. There are few words or phrases that do justice to the soul singing its own revelations. That place is where LAST PSALM AT SEA LEVEL lives, where it is as solid as gold burning itself into light."—Afaa Michael Weaver

Retreat from a Rising Sea: Hard Choices in an Age of Climate Change

Retreat from a Rising Sea: Hard Choices in an Age of Climate Change
by Orrin H. Pilkey (Author), Linda Pilkey-Jarvis (Author), Keith C. Pilkey (Author)


Melting ice sheets and warming oceans are causing the seas to rise. By the end of this century, hundreds of millions of people living at low elevations along coasts will be forced to retreat to higher and safer ground. Because of sea-level rise, major storms will inundate areas farther inland and will lay waste to critical infrastructure, such as water-treatment and energy facilities, creating vast, irreversible pollution by decimating landfills and toxic-waste sites. This big-picture, policy-oriented book explains in gripping terms what rising oceans will do to coastal cities and the drastic actions we must take now to remove vulnerable populations.The authors detail specific threats faced by Miami, New Orleans, New York, and Amsterdam. Aware of the overwhelming social, political, and...

© 2016 BrightSurf.com