Tag Archives: sea level rise

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.

Nares Strait 2012: Tide Gauge Recovered after 9 Years

Andreas Muenchow, Aug.-8, 2012, off Cape Baird

In 2003 we deployed a tide gauge that was recovered today after attempts in 3 different years to do so failed. Discovery Harbor near Fort Conger was the most northern location at 81 42’ North and 64 1’ West of a large moored array placed in 2003. It was at Fort Conger, that Lt. Greeley of the U.S. Army waited in vain for a supply ship that never arrived, but this sad story is for another day and I like to write about happier news: Our 2003 tide gauge lay in wait for 9 years and 1 day precisely. A 2006 attempt to reach this northern location by ship failed on account of heavy ice cover, a 2007 attempt by helicopter succeeded to establish acoustic communications, but failed to recover the sensor package, and a 2009 attempt by ship failed again because of difficult ice conditions.

The odds of a recovery were slim, but 4 hours ago a crew of five found the tide gauge the same way that skilled fishermen of Newfoundland recover lost traps and fish for halibut: with a line of hooks operating small ships smartly. Chief Officer Brian Legge, Seamen Derick Stone and Carl Rose, as well as scientists Ron Lindsay and Jonathon Poole found the proverbial needle (read tide gauge) in the hey stack (read Arctic Ocean). The entrance to Discovery Harbor was guarded by yet another ship-sized piece of Petermann Glacier ice, this one grounded, as well as several large and small sea ice floes, all moving rapidly with the tides and currents. Even navigating the zodiac through this maze to a fixed location was a major accomplishment.

The long-lost tide gauge is a 2 feet cylinder filled with electronics, but 9 years moored to the floor at 20 meter depth turned it into a complex biology habitat attracting wild life much like the artificial reefs created along Delaware by sunken New York City’s discarded subway trains. Mollusks, seaweed, clams, barnacle, algae, and bacterial slime all attached themselves to every surface. Arctic shrimp perhaps feeding on algae or slime were captured along with the gauge. Seaman Derick Stone, who has never seen an Arctic shrimp (neither have I), quickly brushed it away and back into the ocean muttering something about  “Scorpions in the Arctic.” A second specimen was captured alive and returned to the ocean after a brief inspection. It was agreed, that there was no enough meat on this 2-inch long and skinny shrimp

As a sign of respect to the gods of the icy seas a majority of PhDs aboard solemnly swore to give the long lost sensor 3 days of rest before stripping it bare to reveal its guts, check health and status and retrieve recordings. Pranksters aboard this ship, at least one with a PhD, already alerted me to schemes of hostile capture and ransom requests; I suspect ransom to be paid in treasures, valuable certificates, and screech. Little do these pranksters know of web streaming, local area networks, advanced image processing, and other counter-intelligence operations … to be continued.

P.S.: Oh, we also completed section work (temperature, salinity, water samples) in Robeson Channel to the north of Petermann Fjord where a few segments of Petermann Glaciers former ice shelf are both grounded and moving off the coast of Greenland. Presently off Cape Baird to perhaps recover an automated weather station to be placed instead at Joe Island at the southern entrance to Petermann Fjord, weather permitting. We got 40 kts winds from the south, braking waves, as well as balmy air temperatures of 4 degrees Celsius or so.

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 Warming, Melting, and Sliding to Sea

Greenland is warming, Greenland’s warming is melting its ice, and Greenland melting ice is raising global sea level. All true, but it all has happened before during the last 100 years or so. Our technology to extract small signals buried deep in noise from both our backyard and remote Greenland is unprecedented. This skill should not fool us, that the large changes that we see in Greenland and elsewhere have not happened before. They have, but memory is a fickle thing, as “new” is exciting, while “old” is often forgotten and considered unimportant. Those who live in the past are doomed to miss the present, those who ignore the past, are doomed to repeat it. We need to learn from the past, live in the present, and prepare for the future.

Preparing for an expedition to Nares Strait between northern Greenland and Canada in about 5 weeks, I am exploring temperature data from land, satellites, and ocean sensors to get a feel for what has changed. I started with data from weather stations such as the U.S. Air Force Base Thule , Canada’s former spy station Alert, and Denmark’s Station Nord about 700-1000 miles from the North Pole. So, it is cold up there:

Annual cycle of air temperature (bottom panel) from south to north at Thule (red), Grise Fjord (green), Alert (blue), and Cap Morris Jesup. Data years (top panel) for each year day are degrees of freedom. For each place two temperature curves indicate upper and lower limits of the climatological mean temperature for that day at 95\% confidence.

Well, we knew that, but the real question is: Has anything changed? Has Global Warming reached Greenland? The plot above does not tell, but this one does:

Annual averages and trends of air temperature anomalies for the 1987-2010 period for (top to bottom) Station Nord (Greenland), Alert (Canada), Grise Fjord (Canada), and Thule (Greenland). Scales are identical. The trends are fitted to daily, not annual data. The annual averages are shown for display purposes only.

To some it screams: “Warming, melting, Greenland is surging to sea.” [It is, but it did so before.]

There is lots of fancy signal processing that goes into this (see Tamino or a class I teach) to make a firm statement:

The air around northern Greenland and Ellesmere Island has warmed by about 0.11 +/- 0.025 degrees Celsius per year since 1987. North-west Greenland and north-east Canada are warming more than five times faster than the rest of the world.

This must be huge (yes, it is), it must have an effect on the Greenland ice sheet (yes, it does), and this must raise sea level (yes, perhaps 10 cm or 3 inches in 100 years, Moon et al., 2012).

Now where is the catch?

The catch is that my records all start in 1987, because that is the period for which I have actual measurements from all those stations. My satellite record is even shorter: it starts in 2000, but with lots of work can be extended back to 1978. And my ocean record is shorter yet: it starts in 2003. There just are no other hard data available from north-west Greenland.

So, does this mean we are stuck with the gloom and doom of a short record?

No, but we have to leave the comforts of hard, modern data with which to do solid science. People have to stick out their necks a little by making larger scale interferences. Based on the 1987-2010 results shown above, I can now say that trends and year-to-year variations are all similar in Alert, Thule, Kap Morris Jesup, etc., etc., so I will use the 60 year Thule record to make statements that somewhat represent all of Nares Strait. I could also start looking for softer and older data. With soft data I mean sketchy ship logs kept by whalers, tense expedition reports of starving explorers (Lauge Koch, Knud Rasmussen, Peter Freuchen), and imperial expeditions (George Nares, Adolphus Greely).

Further south there are a few ports where government or trading authorities started records early. The current capital of Greenland, Nuuk (formerly Godthab) is such a place. The Nuuk record starts 1881. And what I find is that the current warming in Greenland has happened just as dramatic as it does now in the 1920ies and 1930ies [well, except for the 2010 spike, but that story is still ongoing]:

Data from Nuuk, southern Greenland, where the temperature record goes back to 1881 (monthly data from NASA/GISS). The dashed line indicates 1987.

The trend is statistically significant, about 0.008 +/- 0.03 degrees centigrade per year or about 10 times smaller than what it is for northern Greenland starting in 1987. So the devil of Greenland warming, melting, and sliding to sea is in the details or records that are too short. The Global Warming signal is in there, but how much, we do not know and perhaps cannot know. Furthermore, most of the globe of “Global Warming” is covered by water and the ocean warming we know little about. Recall, my ocean record off northern Greenland only starts in 2003 and ends in 2009 or 2012, if we recover computers, sensors, and data from the bottom of Nares Strait this summer.

Greenland’s data and physics of ice, ocean, and air are exciting and all show dramatic change. To me, this is a big and fun puzzle, but one has to be careful and humble to avoid making silly statements for political purposes that are not supported by data. Do I think Global Warming is happening? Absolutely, yes. Do I think it is man-made? Probably. What do I do about it? I ride my bicycle to and from work every day. And that’s what I do next … bicycle home.

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 …