Hurricane Sandy and a series of noreasters have combined with an apparently unprecedented one year jump in sea level to cause a wave of destruction on the U.S. east coast. The one year change of the average sea level of the North Atlantic ocean from fall 2011 to fall 2012 is about 32mm which absolutely dwarfs the computed trend of 1.7 mm/year since 1992. The approximately 32mm jump is the largest in the satellite altimetry record which began in 1992. 32mm is 1 1/4 inches, not a huge absolute rise, but an unprecedented rise in just one year. These data have not yet been verified and published, they are “live” internet data from NOAA, but the numbers are consistent with other data I have reviewed including big jumps in measured sea levels from tide gauge data (which are highly variable depending on wind speed and direction). I read the numbers off the high resolution graph, so the 32mm value is not precise or verified, but I think it’s in the ballpark.
Sea surface height anomaly maps determined by satellite altimetry show that there was a large positive sea level height anomaly off of the east coast on October 26, 2012 before hurricane Sandy hit. Note that this figure is consistent with reports that the U.S. east coast is a hotspot of sea level rise. The northward expansion of the Atlantic warm pool, pushing the Gulf Stream towards Long Island and southern New England, is apparent in the large anomalies offshore, south of New England. These hot spot anomalies of greater than 25 cm ( about 10 inches ) are what made sea level rise a significant factor in the damage to the east coast. The anomalies off of the mid-Atlantic states are about 8 times larger than the average sea level rise of the north Atlantic.
Hurricane Sandy’s surge and swells damaged North Carolina’s outer banks, cutting off roads to Hatteras Island. Ongoing higher than normal tides have increased the damage to the Outer Banks since Sandy hit. Tides a foot or more above normal have hit the east coast from Miami Beach, to Cape Hatteras to New York obstructing efforts to repair damage from Sandy.
A large change in the winter north Atlantic atmospheric circulation pattern from 2010 to 2012 was one factor that drove the jump in sea level. The North Atlantic Oscillation (NAO) shifted from strongly negative in 2010 to strongly positive in 2012. In years with a negative NAO weaker winds drive less water from the south Atlantic into the North Atlantic. In positive NAO years more water is transported into the North Atlantic, raising sea levels. The shift from strong negative to strong positive NAO had a major role in the sea level jump, but further investigations will be needed to understand why the jump was so large. The extreme La Nina of 2010 also played a role.There was so much anomalous rain over the continents in 2010 that global sea levels dropped briefly. There may be other important factors contributing to the jump in sea level.
A recent research report by Stefan Rahmstorf, Grant Foster and Anny Cazenave using satellite altimetry found that global sea level is rising 60% faster than IPCC forecasts. However, detailed analysis of satellite altimetry maps shows hotspots in the western Pacific, southern Indian ocean and western North Atlantic where sea level rise is taking place at a much higher than average rate. The coastline from Cape Hatteras to Cape Cod, where this fall’s intense storm damage occurred is a sea level rise hot spot. Sea level rise made the damage significantly worse.
Sea level measured by satellite altimeter (red with linear trend line; AVISO data from (Centre National d’Etudes Spatiales) and reconstructed from tide gauges (orange, monthly data from Church and White (2011)). Tide gauge data were aligned to give the same mean during 1993–2010 as the altimeter data. The scenarios of the IPCC are again shown in blue (third assessment) and green (fourth assessment); the former have been published starting in the year 1990 and the latter from 2000.Global sea level rise is very uneven. Grant Foster, a co-author of the sea level rise paper explained in his blog that sea level rise is much faster in some locations than others.
Sea level is by no means “level.” Not only are there small changes in the geoid (the gravitational equipotential surface), the sea itself does not conform to the geoid because of winds and currents, tides and storms. These geographical variations are in addition to the constant fluctuations caused by the exchange of water between land, oceans, ice, and atmosphere, and of course the changes wrought by global warming.
AVISO’s most recent map of sea height anomalies shows that the east coast is one of the word’s regions most highly impacted by sea level rise at this moment.
Videos after the burnt orange croissant:
Hurricane Sandy damaged NC-12, the road to Hatteras, but high tides driven by sea level rise and nor-easters put it under water and destroyed it at Mirlo Beach. This video is from November 14, 2012.
This area, called S-Turns by surfers has great waves that have been rapidly eroding the beach front. There appears to be a lack of shoals directly offshore of this area. To the south, there appears to be a shoal offshore. The offshore shoal may be refracting powerful waves from southeasterly tropical storm swells into S-Turns. To the far north at Oregon inlet, dredging and jetties restrict the flow of sand flowing south. Pea Island, which is south of the inlet has been losing beachfront to the rising seas. S-turns is at the southern boundary of the receding Pea Island shoreline. This situation makes S-Turns a hotspot. NCDOT has repeatedly filled in the area at S-Turns, but the ocean continues to attack it. Sea level rise is the underlying factor that is slowly defeating all engineering efforts to maintain the road.
Locals who don’t understand global warming, sea level rise and local coastal processes are proposing to “renourish” the beach, but erosion rates are so high in the Rodanthe area that it would be like burning money to keep warm. A new inlet is forming at the surf spot known as S-turns and we’re not going to be able to stop it.
Here’s the Serendipity House back in 2009, where “Nights in Rodanthe” was filmed. This spot is now in the ocean. The wrecked NC-12 road is west – landward and north of this spot where Serendipity was. Serendipity was moved a few years ago before the waves would have torn it apart.
This used to be one of the most famous surf spots on the east coast. It is now an inlet that the NCDOT is trying desperately to close up.
Americans love their beaches, but they aren’t acting to stop climate change.
All of our beaches are threatened by climate change and sea level rise. Pumping sand from offshore won’t stop the rising tides and it won’t save our beaches. Denying sea level rise as North Carolina’s Republican legislators have done is worthy of ridicule. They have made fools of themselves.
If we are serious about saving our beaches (and our coastal cities like New York City) we need to get serious about stopping greenhouse gas emissions. Sooner or later all of our beaches will look like Mirlo Beach if we don’t slash emissions.
This post comes from a scientist who finds himself to be a Fish Out Of Water. In a related story, see When it comes to SLR, conservatism is (unrealistic) optimism