Shrinking ice caps and an alarming increase in rate of sea level rise cause growing concern about coastal erosion, storm-surge flooding, surface water quality and socio-economic impacts.Scientists may not agree on what is causing the extremely rapid rise in sea level over the last 10 years, but the effects on the world’s coastlines, including Maui’s, is undeniable.
According to Maui Coastal Processes Extension Agent Zoe Norcross-Nu‘u, for every unit of sea level rise, 125 units of beach loss occurs. For example, if the sea rises one foot, Maui will lose 125 feet of sandy shoreline. In the last 100 years, sea level has risen one meter (a little over 3.25 feet), swallowing up 125 meters (over 440 yards, or the length of more than four football fields) of now lost Maui beach.
According to the Intergovernmental Panel of Climate Change, the effects on coastal environments are numerous. Increased beach and coastal erosion, higher storm-surge flooding and changes in surface water quality are just a few of the biophysical impacts. This can result in a loss of tourism, recreation and transportation functions as our cultural resources dissipate.
Norcross-Nu‘u explained that it’s difficult to link global warming specifically with sea level rise, and some scientists deny that it even exists. But with the melt rate faster than our worst-case scenario, and the fact that scientists have underestimated the rate so badly, she said “it just seems so obvious!”
Since March of this year, scientists have been urgently researching what has become an extremely rapid rise in sea level over the last 10 years. A startling amount of ice is slipping from the polar ice caps in Antarctica and Greenland into the sea, tripling the rise, and taking the experts completely by surprise.
According to Dr. Isabella Velicogna, a research scientist with the University of Colorado, the Antarctic ice sheet is losing a significant amount of mass; about 152 cubic kilometers per year, which is equivalent to the amount of water the U. S. uses in three months.
The Gravity Recovery and Climate Experiment (GRACE) has found that the ice caps are shrinking from above and below. “The warmer ocean comes underneath the ice shelves and melts them from the bottom,” said NASA Glaciologist Dr. Jay Zwally. “Warmer air melts them from the top, so they’re thinning, and eventually they get to a point when they go ‘poof.’”
There is an increasing realization within the science community that this “warmer air” is due to global warming. In Greenland, radar scientists Eric Rignot and Paniir Kanagaratnam discovered that ice melting from the Greenland ice sheet, three kilometers thick, has doubled in speed in just the last few years.
Maui is already suffering from beach deterioration, not only due to the rise in sea level, but from human behaviors that have caused major damage to coral reef systems and sand dunes. Notably, due to their close proximity to the shore, the onslaught of developments on Maui has caused a decline in beaches. As water levels rise, sea walls are sometimes erected to protect property as water encroaches. Sea walls, however, can often destroy beaches as they block movement of inland sand that would otherwise replenish the beach.
One way to save the beaches is to replenish the beach with sand from elsewhere, which is expensive and usually requires constant maintenance, according to Norcross-Nu‘u. And Maui’s sand, which has been exported to O‘ahu for the last few decades, is possibly on the verge of extinction in five to seven years, unless exportation is halted, according to the Maui Inland Sand Resource Quantification Study.
In some cases, such as the beach at Kama‘ole III, foot traffic has affected the natural sand dunes so badly that deep ravines have formed over time, allowing the sand to be blown into the grassy park areas. If the foot traffic continues, the beach will disappear sooner than later. Kihei-Wailea Rotarians Bob and Lis Richardson took it upon themselves to replenish the sand and reform the dunes. In this instance the dunes will have the opportunity to shift and replenish naturally.
Another option is to relocate the buildings mauka, so beaches can replenish themselves from inland dunes. The Maui County Planning Commission recently updated Shoreline Setback Rules, which require properties to be built 50 times the annual erosion rate, plus 20 feet away from shore. This new rule, of course, is based on the erosion rate over the last 100 years. With new evidence of a much-accelerated rate, Norcross-Nu‘u said, “these setbacks may not be nearly enough.”
Geoscientist Michael Oppenheimer from Princeton University said that “the greenhouse gases that people are spewing into the atmosphere this century might guarantee enough warming to destroy the West Antarctic and Greenland ice sheets, possibly as quickly as within several centuries.” Simply put, sea level would rise five to 10 meters, at rates not seen since the end of the last ice age. Considering that it has only risen one meter in the last century, and researchers are baffled as to what will happen next, global warming has become a major cause for concern.
All of the current concern about global warming has yet to inspire a current solution. In 1997, the United Nations Framework Convention on Climate Change (UNFCCC) created the Kyoto Protocol, an agreement “to reduce the emissions of carbon dioxide and five other greenhouse gases, or engage in emissions trading if they maintain or increase emissions of these gases.” Of the 163 countries that have signed the treaty, only those who ratify the agreement commit to reduce their emissions. The U.S. has signed, but not ratified the agreement, even though it releases more greenhouse gases than any other nation and accounts for more than 25 percent generated by humans worldwide. According to Norcross-Nu‘u, the treaty is “politically unpopular” because of its great expense, despite its long-term economic benefits.
NASA Earth Science Director James Hansen made the chilling statement that “if we pass a certain point of no return, then we’re going to get large sea level rise, and even though it would take a century or two or three to play out fully, we will have started a process we just can’t stop.”
“We don’t know what all the implications are, but it is clear we need to do something,” said Norcross-Nu‘u. “We are nowhere near curbing our greenhouse gas-producing habits.”