The Chickahominy Report

News about Earth, Atmosphere, Water, and Life

New study suggests U.S. coasts may see greatest sea-level rise

Eastern Shore National Wildlife Refuge

Coastal wet­lands such as those in Vir­gini­a’s East­ern Shore Nation­al Wildlife Refuge will be dev­as­tat­ed by sea-lev­el rise from melt­ing ice sheets. (Copy­right © 2008 David M. Lawrence)

MECHANICSVILLE, Va. — A study in last week’s edi­tion of the jour­nal Sci­ence sug­gests that sea lev­els may not rise as much as pre­vi­ous­ly pre­dict­ed under like­ly sce­nar­ios of human-caused cli­mate change, but that the ris­ing water lev­els will be dev­as­tat­ing enough as it is.

Even more wor­ry­ing for res­i­dents of the Atlantic and Pacif­ic coasts of the Unit­ed States, the ris­ing lev­els will be 25 per­cent high­er than in most oth­er parts of the world’s oceans.

Most of the sea-lev­el rise will come from the col­lapse of the West Antarc­tic Ice Sheet, which is already show­ing signs of breakup along its fringes. While pre­vi­ous stud­ies had assumed a com­plete col­lapse of the ice sheet, the study by a team of British and Dutch sci­en­tists sug­gests a com­plete col­lapse is unlike­ly.

Much of the land por­tion of the West Antarc­tic Ice Sheet is locked in by ice shelves along the fringes of the con­ti­nent.  As the sea ice melts, the for­mer­ly land­locked ice can slide eas­i­ly into the Wed­dell and Ross seas. A com­plete col­lapse of the ice sheet would trig­ger sea-lev­el ris­es of 5 to 6 meters (16 to 20 feet).

Jonathan Bam­ber (Bris­tol Glacio­log­i­cal Cen­tre, Uni­ver­si­ty of Bris­tol, Bris­tol, UK) and col­leagues from the Delft Uni­ver­si­ty of Tech­nol­o­gy in the Nether­lands and the Uni­ver­si­ty of Durham in the Unit­ed King­dom exam­ined the bedrock beneath the ice sheet to deter­mine how that might affect the amount of ice flow­ing into the sea.

The most vulnerable portions of the West Antarctic Ice Sheet rest on bedrock in basins that are below sea level. (United States Antarctic Program)

The most vul­ner­a­ble por­tions of the West Antarc­tic Ice Sheet rest on bedrock in basins that are below sea lev­el. (Unit­ed States Antarc­tic Pro­gram)

Most of the vul­ner­a­ble ice is locat­ed on bedrock that forms basins that lie below sea lev­el. Where that bedrock slopes down­ward inland, the researchers assumed that the ice will start float­ing on the water that begins to fill those basins, form­ing ice sheets fur­ther inland that will like­wise break up and trig­ger fur­ther col­lapse. On the oth­er hand, Bam­ber and his asso­ciates assumed that ice ground­ed above sea lev­el, or locat­ed on bedrock that ris­es inland, would remain intact. Under this sce­nario, glob­al sea lev­el rise would aver­age only 3.3 meters (11 feet).

The vol­ume of water added to the world’s oceans isn’t the only prob­lem. The shift of mass from Antarc­ti­ca to the oceans would affect region­al vari­a­tions in the the Earth­’s grav­i­ty field, weak­en­ing the grav­i­ty field in the South­ern Hemi­sphere and strength­en­ing it in the North­ern Hemi­sphere. The redis­tri­b­u­tion of mass would like­wise affect the Earth­’s rota­tion.

As a result, water would pile up in the north­ern oceans — espe­cial­ly along the Atlantic and Pacif­ic shores of North Amer­i­ca — as well as in the Indi­an Ocean. In those regions, the sea lev­el rise would be as much as 25 per­cent greater than the glob­al aver­age. In oth­er words, sea lev­els along the shores of the Unit­ed States could rise by 4 meters (14 feet). While the full extent of the ice sheet breakup would take sev­er­al cen­turies, sea lev­els could rise be near­ly 1 meter (3 feet) by the end of this cen­tu­ry.

Much of the Mid-Atlantic coast, with its gen­tly slop­ing beach­es, would not fare so well, even with the rel­a­tive­ly small amount of sea lev­el rise by the end of the cen­tu­ry. By the time the full effect of the ris­ing seas are felt, many major cities along the East Coast will be dev­as­tat­ed.

For exam­ple, much of Hamp­ton Roads, includ­ing large por­tions of Fort Eustis, Hamp­ton, New­port News, and Poqu­o­son — and vir­tu­al­ly all of Fort Mon­roe Mil­i­tary Reser­va­tion, would be inun­dat­ed. To the south, much of Nor­folk, Portsmouth, and Naval Sta­tion Nor­folk would like­wise be inun­dat­ed. As the largest navy base in the world, flood­ing there would have dire con­se­quences on U.S. nation­al secu­ri­ty. Vir­ginia Beach and sur­round­ing areas would like­wise be hard hit, with Vir­ginia Beach’s water­front hotel strip large­ly flood­ed.

Our nation’s cap­i­tal region would also suf­fer. On the Vir­ginia side of the Potomac, Alexan­dri­a’s water­front as well as much of Ronald Rea­gan Wash­ing­ton Nation­al Air­port would be under­wa­ter. Across the riv­er, much of Bolling Air Force Base and Wash­ing­ton Navy Yard would be under water, as would Ana­cos­tia Park, East Potomac Park (includ­ing Hains Point). Por­tions of the Mall — includ­ing the Jef­fer­son and Franklin Delano Roo­sevelt memo­ri­als and the Reflect­ing Pool — endan­gered. The Lin­coln Memo­r­i­al would like­ly sur­vive as a small island. The edge of the Viet­nam Vet­er­an’s Memo­r­i­al may remain above sea lev­el, but waves would like­ly turn the walk­way to the cen­ter of the mon­u­ment into a small pond.

So, no mat­ter whether there is 4 meters of sea lev­el rise or 6 meters, the pop­u­la­tion in parts of the Mid-Atlantic region will suf­fer, and key cul­tur­al and envi­ron­men­tal resources will like­ly be lost unless con­crete action is tak­en to head off the specter of glob­al warm­ing.

— David M. Lawrence

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1 Comment

  1. Nice expla­na­tion of the lat­est sci­ence behind SLR. I report­ed SLR in the Pacif­ic North­west. Tec­ton­ic uprise will com­pen­sate giv­ing them more pro­tec­tion than the coast­lines you report here. Unless con­crete action is tak­en very very soon it’s time for our kids to start a cli­mate rev­o­lu­tion and take mat­ters into their own hands, while there is some­thing still worth tak­ing.