By Craig Jones
Earlier this year, I was confronted head-on with some of the coastal engineering math I plowed through in college. The swell was topping out over 20 feet at the offshore Monterey Bay NOAA buoy. On top of that, spring tides were bringing the tides over 6 feet at the morning high tide. I saw all of this during my ritual morning check of the waves when I took the coast road to work. As I turned the corner to the lower lying Corcoran Lagoon, the sight was something to behold as the full fury of these waves unleashed on the beach and roadway.
During the summer, and typical winter, there is over 100 yards of beautiful yellow sand beach at Corcoran Lagoon. The first few large 15 feet+ El Niño swells in the Fall made short work of this, leaving only a small beach in front of the road. By the time I turned the corner on that big morning, there was no beach visible, only huge whitewater cascading over the road. As I watched, I saw the 500-lb+ stones that had been placed in front of the roadway to armor it against just such waves, easily lifted 6 feet up the embankment and onto the roadway. The waves at high tide were scooping up these massive armor stones and moving them around like Styrofoam peanuts in the wind! Seeing this made me think back to my engineering classes and calculating the size of armor stones needed for particular waves. I also remember being a skeptic when I came up with numbers like 2 tons. Not a skeptic anymore!
Over 120 million people, in the United States alone, live on the coast. Worldwide about 40 percentof the population lives near the coast (1) which tops out at near 3 billion people! That’s a lot of people that are directly affected by anything going on in our oceans. It’s certainly natural that we should be thinking about things like big El Niños, hurricane seasons, and sea-level rise. The coincident occurrence of any of these events can have disastrous consequences (think Hurricanes Katrina, Sandy, and the present El Niño). At the end of the day, our coasts are in danger and it’s important for use to understand why so we can figure out what to do.
In the past century, the ocean is definitely warming up and from all the best scientific analysis it is going to continue to do so. The figure below shows compiled data from NOAA on the sea surface temperature anomalies and change from the average temperature, by year, for the last 65 years (2). The trend is fairly apparent that we are getting warmer.
So what are the effects of all this warmer water? Heat is energy, and the ocean is an excellent storage vessel for that energy. Short-term climate patterns, such as El Niño, are fundamentally related to heat in the ocean. Doing some hand waving, more heat in the ocean equals a bigger El Niño! Considering that a large El Niño can raise coastal sea levels an additional 3 inches to 1 foot, combined with big storms, it makes sense that the change of temperature in the ocean is something we should pay attention to. Figure 2 shows an example during the 1983 El Niño that water levels in San Francisco Bay were up to 1.5 foot higher due to winds and waves during the bigger storms (3). That’s a lot of extra water getting pushed into the Bay.
Getting away from the hand waving, a study by Lowe and others (4) suggests that there is no definite relationship between climate change and storm intensity. But what does the past data really show? Modeling has shown that the North Atlantic has and will experience significant increases in wave heights (5). The researchers have attributed this change to larger low pressures systems. In other words, bigger storms!
Before this winter, the largest El Niño on record was in 1997. As of February 2015, the present El Niño is on track to be at least equal to, if not greater in intensity than the 1997 El Niño. I can tell you from the Santa Cruz, California, standpoint, we’ve had a string of big swells unlike anything most local surfers have seen. The famous Maverick’s big wave surfing spot saw some of the best waves ever this February as discussed here in Surfing magazine (6). Not mention some epic waves during the Titans of Mavericks contest won by one of our local Santa Cruz surfers, Nic Lamb. Also, the Eddie Aikau big wave contest in Waimea Bay, Hawaii had some of the best and most consistent waves most contestants had ever seen.
Bigger Storms…So What?
We have potentially bigger waves and larger storms occurring in the Pacific due to El Niño and more frequent storms in the Atlantic. More storms mean more storm surge. A storm surge is a rapid rise of the water level, almost tsunami-like, during a large low-pressure storm system (e.g., a hurricane). The storm surge is superimposed on top of the tide, so a big storm surge combined with a high spring tide can substantially increase water levels. The most causalities and damage during hurricanes and cyclones happen because of the storm surge. If you need any ideas about the damage from a storm surge, think Manhattan Island during Sandy or New Orleans during Katrina.
The Geophysical Fluid Dynamics Laboratory is a group within NOAA that investigate various climate change scenarios using models to figure out what the effects of all these changes are. A significant result they’ve seen in their simulations is that by the end of the 21st century, tropical storms (hurricanes and cyclones) will be more intense (7). More intense means a much more destructive force when the storm hits land, essentially we take a disaster and make it bigger.
A Rising Sea
We’ve been talking about waves and water levels during storm events, but underneath it all there’s sea level rise that’s also simulated in these models. To get an idea of the effect, we only need listen to experts talk about lower lying coasts. “If sea level rises another foot,” said Duke University beach expert Orrin Pilkey in an interview (9), “the shoreline in northeastern North Carolina could be pushed back 5 or 6 miles and all of the projections I’ve seen suggest it will be more like 3 feet by 2100.”
There are two primary reasons for the warming-induced sea level rise we are seeing now. First, warm water expands, and when it expands the sea level has to rise. Second, warm water melts ice and the increased amount of water also causes the sea level to rise. The IPCC (10) estimates that global sea level rose an average of 1.7 mm per year over the 20th century. The last years of the 20th century increased to 3.1 ± 0.7 mm per year. That’s nearly double the rate in recent years! The IPCC (10) projects 18–59 cm with an additional 17 cm if rapid changes in ice are included. We’re talking up to 76 cm (nearly 2.5 ft) globally. This is actually lower than other recent credible projections of 78–175 cm (up to 6 ft). Example projections of sea-level rise to 2100 are from IPCC global climate models (pink shaded area) and data analysis methods methods (gray shaded area; 11).
Let’s just say on average it’s a meter (3 feet) of sea level rise. What does that mean? A close colleague of mine and a coastal scientist here in Santa Cruz, Dr. David Revell, summarized it succinctly: “Sea-level rise will increase the risks associated with coastal hazards of flooding and erosion.” While that may not seem alarming, they predict 214 square kilometers (83 square miles) of land eroded by 2100 under sea level rise scenarios in California alone (12). That seems like a lot — and remember California is not considered a low-elevation state relative to sea level.
A summary from NOAA in the figure below on the amount of land already lost along the Atlantic coast in less than 20 years is striking (13). On the website (which you should browse around for more specific information), NOAA talks in terms of “converted to open water”. Not too comforting if you live on the coast, which 40 percent of our population does. If we think about this in terms of accelerating sea-level rise coupled with bigger storms, there are some potentially big consequences here.
What Is Needed?
The severity of impacts from these changes fundamentally depends on the exposure (e.g. elevation) and vulnerability. By impacts we mean events that have the potential to produce widespread damage and can disrupt the functioning of communities (14), even those the size of New York City.
While we acknowledge natural variability in the climate, we can’t discount human-induced climate change.
Events like the 2015 Paris United Nations Conference on Climate Change are bringing countries together to reach agreements on how to reduce climate change. Also, adaptation and mitigation of communities is necessary to reduce the risks of climate change.
One place we desperately need help is in gathering information on the ocean. From ocean temperature to wave heights, it is critical that we develop these long-term datasets so that scientists can really understand the size and frequency of destructive events. Organizations like opensource.com are facilitating all manner of open data and citizen science that can be applied to the ocean (15).
Through better understanding, our communities can implement measures to reduce the damage caused. At the end of the day, this means money and effort are better spent before a disaster instead of continuing with a wait and see attitude, which many communities presently practice.
Dr. Craig Jones is an ocean and environmental engineer, writer, blogger, surfer, and inventor living in Santa Cruz, CA. He is the inventor of The WaveClock hardware and app. His key areas of interest are in ocean and environmental sciences. His primary work focuses on developing and implementing field and modeling studies on transport processes in all aquatic systems from rivers to the open ocean. Craig’s goals are to continue to find unique and efficient solutions to these problems through continued work with a wide variety of colleagues and clients. Check out The WaveClock at www.thewaveclock.com.
1. “What Percentage of the American Population Lives near the Coast?” What Percentage of the American Population Lives near the Coast? NOAA, 7 Feb. 2014. Web. 07 Feb. 2016.
2. NOAA National Centers for Environmental Information, State of the Climate: Global Analysis for Annual 2011, published online January 2012, retrieved on February 7, 2016 fromhttp://www.ncdc.noaa.gov/sotc/global/201113.
3. Dalrymple, Robert A., et al. “Sea-Level Rise for the Coasts of California, Oregon, and Washington: Past, Present, and Future.” National Research, Council. The National Academies Press Washington DC, 2012.
4. Lowe, J.A., P.L. Woodworth, T. Knutson, R.E. McDonald, K.I. McInnes, K. Woth, H. von Storch, J. Wolf, V. Swail, N.B. Berier, S. Gulev, K.J. Horsburgh, A.S. Unnikrishnan, J.R. Hunter, and R. Weisse, 2010, Past and future changes in extreme sea levels and waves, in Understanding Sea-Level Rise and Variability, J.A. Church, P.L. Woodworth, T. Aarup, and W.S. Wilson, eds., Wiley-Blackwell, UK, pp. 326-375.
5. Bertin, Xavier, Elizabeth Prouteau, and Camille Letetrel. “A significant increase in wave height in the North Atlantic Ocean over the 20th century.”Global and Planetary Change 106 (2013): 77-83.
6. “Yesterday At Maverick’s | SURFING Magazine.” SURFING Magazine. N.p., 05 Feb. 2016. Web. 07 Feb. 2016.
7. “GFDL – Geophysical Fluid Dynamics Laboratory.” Geophysical Fluid Dynamics Laboratory. N.p., 30 Sept. 2015. Web. 07 Feb. 2016.
8. Johnna Rizzo, for National Geographic News PUBLISHED Fri Nov 02 02:12:00 EDT 2012. “After Sandy’s New York Deluge, a Flood of Rats?” National Geographic. National Geographic Society, n.d. Web. 07 Feb. 2016.
9. “Climate Change, Sea Level Rise Spurring Beach Erosion.” Climate Change, Sea Level Rise Spurring Beach Erosion. N.p., 27 May 2012. Web. 07 Feb. 2016.
10. IPCC, 2007, Climate Change 2007: The Physical Science Basis, Contribution of Working Group I to the Fourth Assessment Report of the IPCC, S. Solomon, D. Qin, M. Manning, Z. Chen, M. Marquis, K.B. Averyt, M. Tignor and H.L. Miller, eds., Cambridge University Press, Cambridge, 996 pp.
11. Rahmstorf, S., 2007, A semi-empirical approach to projecting future sea-level rise, Science, 315, 368-370.
12. Revell, D.L., R. Battalio, B. Spear, P. Ruggiero, and J. Vandever, 2011, A methodology for predicting future coastal hazards due to sea-level rise on the California Coast, Climatic Change, 109, S251-S276.
13. “Digital Coast. More than Just Data.” Evaluating Land Loss from Sea Level Rise along the Atlantic Coast. N.p., May 2014. Web. 08 Feb. 2016.
14. Field, Christopher B., ed. Managing the risks of extreme events and disasters to advance climate change adaptation: special report of the intergovernmental panel on climate change. Cambridge University Press, 2012.
15. Hibbets, Jason. “Surfing the Open Data Wave.” Opensource.com. N.p., 3 Oct. 2011. Web. 07 Feb. 2016