Tag Archives: predictability

Rules of Engagement: Ships, Science, and Democracy

The FS Polarstern will leave port tomorrow night for scientific work between Greenland and Spitsbergen near 79 degrees north latitude about 1200 km or 770 miles from the North Pole. It will be hard work, Continue reading

Fish, Fashion, and Climate: Simple Thoughts on Complex Systems

I love pickled herring, but the fashion of eating this delicacy varies with changing cultures and climates. In northern Europe it used to be a standard fare, perhaps still is, but in my native coastal North-Germany it was poor man’s food Continue reading

Rising Seas, Storms, and Flooding

Ocean waters are rising and flooding inland waters in Delaware and elsewhere. Some of this is perfectly regular and normal such as the up and down of the tides. Some of it is irregular and normal such as caused by storms, river discharges, waves, and weather. And some is caused by global warming as we continue to burn coal and oil to power our economies. Lets have a quick look at what all this looks like and try to put this into some perspective, but Sandy’s 5.3 feet surge last monday was second to the 5.5 feet surge that hit Lewes in 1962.

Cedar Street in Lewes flooded on Monday, October 29. (Photo by: Don Bland), as published by Cape Gazette.

The up and down of the tides each day is about 3 feet in Lewes, Delaware. This large change in sea level is so regular, normal, and predictable, that I remove it from all further discussion, because I want to know how extreme an event this week’s storm Sandy was. For this purpose I downloaded all the hourly tide gauge data from Lewes, Delaware from NOAA. The record starts in 1957 and is ongoing. Here is how the record looks for the last 4 weeks including the surge caused by Sandy last monday:

Sandy’s storm surge added 5.3 feet to the regular tide which is second-largest surge in the historical record. The largest surge at Lewes, DE was caused by the 1962 Ash Wednesday Storm that added 5.5 feet to the regular sea level:

So while Sandy was a very large surge, it was neither unprecedented nor a once in a century event. Furthermore, and this is where I come back to global warming, the 5.3 feet 2012 surge of Sandy includes the last 50 years of steady sea level rise which comes to about an inch every 10-15 years or about half a foot in the ~50 years between 1962 and 2012. So, a repeat of the 1962 storm system would cause a 6.0 feet and not the 5.5 feet surge that took place in 1962.

Furthermore, while the real size of the surge depends on where the center of the storm makes land-fall or where you are relative to the storm, the rising seas caused by global warming are much more uniform, that is, they are little different in Boston, New York, Lewes, Norfolk, or even San Francisco:

So, global warming and the rising seas it causes are both real and here to stay. Global warming provides the upward creeping background sea level to which larger tides, waves, and surges add. The combined effect of all these cause the coastal flooding. So 50 years from now, a rare, but perhaps perfectly natural freak storm like Sandy will cause a storm surge of 5.8 instead 5.3 feet on account of global warming. About 1/3 of this added sea level is caused by the oceans expanding as they warm, another 1/3 is caused by melting glaciers and ice sheets in Greenland and Antarctica, and the last 1/3 is caused by other processes. So, what happens on Greenland or China does not stay there, it impacts present and future sea level in Lewes, DE.

Oceanography of Petermann Fjord and Glacier Melting

Trudy Wohlleben just send a group of scientists in Denmark, England, Canada, and the US the latest RADARSAT image of the ice island that formed in Petermann Glacier earlier this week.

RadarSat Image of Petermann Ice Island (PII-2012) and Glacier kindly provided by Trudy Wohlleben, Canadian Ice Service. The location of the hinge line is approximate only.

The current position of the remaining ice shelf of Petermann Glacier is the farthest landward since recorded observations. Dr. Croppinger was the first to provide a map of the glacier Continue reading

Greenland’s Glaciers, Science, Sea-Level, and Teachers

Science Magazine hit climate change hard today. They cover how Greenland’s glaciers and ice sheets change as they interact with the ocean and contribute to sea-level rise feature in 3 related stories. The reality check of these three stories puts a damper on the usual doomsday scenarios of those whose skill is limited to grabbing public attention to move a political agenda. Real science works differently:

May-4, 2012 Science Magazine Cover: A jumble of icebergs forms in front of the heavily crevassed calving front of Jakobshavn Isbræ, one of the fastest outlet glaciers draining the Greenland Ice Sheet. The ~5-kilometer-wide ice front rises ~80 meters out of the water and extends more than 600 meters underwater. Recent research shows that the speeds of Greenland glaciers are increasing. See page 576. [Photo Credit: Ian Joughin, APL/UW]

The solid new research is that of Twila Moon, a graduate student at the University of Washington whose dissertation work relates to the evolution of Greenland’s outlet glaciers over the last 10 years. She uses data from Canadian, German, and Japanese radars flown on satellites. She applies fancy mathematics to the data and feds data and mathematics into modern computer codes. And with all that, she cracks the puzzle on how fast more than 200 of Greenland’s largest glaciers go to town, eh, I mean, to sea. Furthermore, she shows how this flow has changed over the last 10 years.

Twila Moon, graduate student and scientist at the University of Washington and first author of “21st-Century Evolution of Greenland Outlet Glacier velocities” that appeared in Science Magazine on May-4, 2012. [Photo Credit: APL/UW website]

Back in the days of 2008, crude, but simple back-on-the-envelope calculation suggested that Greenland contributes 0.8-2.0 meters to global sea-level rise by 2100. In stark contrast, the 2000-2010 data now reveals, that even the low-end estimate is too high by a factor of 10. A glacier here or there may accelerate at a large rate to give the 0.8-2.0 m, but these rates do not occur at the same time at all glaciers. Ms. Moon’s more comprehensive and careful analyses of accelerating glaciers bring down Greenland’s contributions to sea-level rise to below 0.1 m by 2100, that comes to about 1 mm/year or an inch in 30 years.

A commentary written by Professor Richard Alley relates to the ice-sheets that feed these glaciers. Dr. Alley is famous for his work on Greenland’s ice sheet as he participated in 2-Mile Time Machine, a project that revolutionized the way that we view climate and its variability the last 100,000 years. The title refers to the 2-mile long ice-core from Greenland’s ice-sheet that trapped and stored air and stuff from the last 100,000 years. Dr. Alley is also featured in Andrew Revkin’s dot-earth blog of the New York Times as the Singing Climatologist. His comment on “Modeling Ice-Sheet Flow” references Ms. Moon’s observations as evidence that ice sheets change quickly. It also contains the sentence that “The lack of a firm understanding of ice-sheet-ocean interaction, constrained by reliable ocean data, remains a critical obstacle to understanding future changes.” I could not agree more with this sentiment, these data are darn hard to come by … not as hard as getting to the bottom of the 2-mile time machine, though.

While Ms. Moon addressed changes in Greenland’s glaciers, Dr. Alley addressed the ice-sheets feeding those glaciers, another comment by physical oceanographer Dr. Josh Willis of NASA’s Jet Propulsion Laboratory relates to the sea-level changes caused by accelerating glaciers to make “Regional Sea-Level Projections.” He works mostly on massive computer models which devour massive amounts of data to get climate right. Sometimes this works, sometimes is does not, but he does comment that these earth system models give sea-level projections that are a factor 2 smaller than those derived from statistical relations and semi-empirical models using surface temperature and radiative forcing to extrapolate past trends into the future. The difference probably relates to smaller and more regional processes that involve the physics of ocean circulation and its interaction with ice-shelves off Antarctic and Greenland.

Dr. Josh Willis conducting an oceanographic experiment studying sea temperatures between New Zealand and Hawaii. [Credit: JPL/NASA]

My great oceanography hero, Henry Stommel of Woods Hole oceanographic Institution once wrote in his “View of the Sea,” that “Science is both an individual and a social activity.” I am sure that graduate student Ms. Moon, NASA researcher Dr. Willis, and veteran professor and science communicator Prof. Alley all work hard and lonely at night some nights … and party hard while discussing science and adventures over a beer, dinner, coffee in some city, remote field, or on a ship. The one group of people missing in this picture are … the science teachers, that is, those dedicated, over-worked, and under-paid professionals who encourage, motivate, and helped us to become scientists before we went to college.

The editorial of this week’s Science Magazine is entitled “Empowering Science Teachers.” It compares the social and professional status of pre-college science teachers in Finland and the USA. I will only say in the words of Anne Baffert, chemistry teacher at Salpointe Catholic High School in Tucson, Arizona, that too many science “… teachers work in a command-and-control environment, managed by those who lack any real understanding of how to improve the system.” The editorial suggests on how scientists can improve science teaching, such as “… active involvement in science through structured collaborations with scientists …” Apparently, Finland succeeds while we in the USA are challenged to get our graduate students into a pre-college class room teaching. More stuff for me to munch on here …