Climate Change and Kauai

SUBHEAD: A look at global warming forecasts and how they will affect Hawaii and specifically Kauai.  

By Juan Wilson on 22 November 2009 for Island Breath -
(http://islandbreath.blogspot.com/2009/11/climate-change-and-kauai.html) 

 
Image above: Rain strata in Kauai as affected by global climate change into the future. Graphic by Juan Wilson from content of presentation by Dr. Thomas Giambelluca.

Yesterday, from 9:00am to 1:00pm at Kauai Community College a symposium was held titled "Global Climate Impacts on Kauai". The day's events were sponsored by the Surfrider Foundation, the University of Hawaii Sea Grant College Program and KCC. Dr. Carl Berg, from Surfrider Foundation Kauai, hosted. The subjects and speakers were:  

Climate Overview: Rainfall and Drought
Dr. Thomas Giambelluca, University of Hawaii Geography Department  

Water: Stream Flow & Groundwater
Dr. Gorden Tribble, US Geological Survey  

Sea Level Rise: Coastal Problems
Dr. Chip Fletcher, University of Hawaii Geography Department  

Ocean Changes: Coral Reefs
Dr. Paul Jokiel, University of Hawaii Institute of Marine Biology This event was streamed live on the internet and is currently archived for view at http://www.ustream.tv/recorded/2610138.  

Rainfall and Drought
The presentation by Dr. Thomas Giambelluca demonstrated that most rain arriving on Kauai is created by moisture carried by the Trade Winds as the air rises on the mountain sides within a strata below a phenomena called the Trade Wind Inversion (TWI), and above a strata with high relative humidity called the Lifting Condensation Level (LCL).

The Trade Wind Inversion (TWI) is not always present. The clouds are thinner when the TWI is present, and there is less rain. A doctoral student at UH has recently demonstrated that in the past, on average the TWI was present about 80% of the time. But in the past 20 years, the TWI has been present 90% of the time, and there has been less rain during that period.

The elevation of the TWI also has an effect on the amount of rainfall we get. When the TWI is higher, there is more rain, when it is lower there is less rain. The LCL elevation is the result of Relative Humidity over the land. If temperature on the land is high, the Relative Humidity will be low and the LCL will be at a higher elevation.

The higher the LCL, the less volume of rainclouds will be over the land. Dr. Giambelluca indicated that the macro changes in global climate will raise the temperature of the Pacific Ocean in the area of Hawaii, but that temperatures over land will rise faster than over the ocean, thus reducing relative humidity over the island of Kauai and raising the elevation of the LCL. If conditions exist for a persistent low TWI and a high LCL, then Kauai wil get less regular rain.  

Stream Flow & Groundwater
Dr. Gorden Tribble spoke about Kauai's fresh water aquifers that provide storage for rainwater and feeds perennial streams. He used data collected by USGS and other sources to demonstrate that a little less rainfall means a lot less recharge of our aquifers (refilling of the water table).

The Lihue Aquifer (Puna Moku) has received only 53% of its normal rain in recent years. This translates to on a 38% recharge rate to its water table. Moreover, the irrigation of large areas of sugarcane is no longer occurring on Kauai. Although sugarcane depleted soil, irrigation increased the return of water to the aquifer (rather than letting it go to runoff into the ocean).

A negative feedback loop could be created if less rainfall reduces forest fauna and consequently increases runoff even further. It is likely that Kauai will have a disproportionally smaller storage of fresh water due to a modest reduction of rain.  

Coastal Problems 
 Dr. Chip Fletcher had data to indicate that ocean levels had risen about 6" during the 20th century. He said that since 1960 about 2500 cubic miles of ice have melted. He presented several scenarios of likely global warming affects through the 21st century. They varied from models that actually showed increased ice pack and lowering seas to the melting of Iceland and Antarctica leading to over 30 meters (100 feet) of ocean rise this century.

However, he concluded that mainstream models of global temperature rise seem to converge on about a one meter rise before 2100AD. Even this "small" rise in sea level will have a dramatic effect on the low lying flat areas of Kauai during storm surges and high-high tides. These areas, of course are where it is convenient for many people to live and where many towns and resorts are located.

Inundations of salty ocean water during a storm surge can destroy crop lands as well as damage infrastructure. This is particularly true in places like Kekaha, Waipuoli, and Hanalei. The rising ocean will erode away sandy beaches. Beach sand is a product of a slow process of grinding down of land with rich calcium deposits. Beaches take longer to create than the speed the oceans will rise.

 Coral Reefs
Dr. Paul Jokiel examined effects on coral reefs. He showed that due to the deep oceans surrounding Hawaii and factors related a lack of upwelling of nutrients from the lower depths, that Kauai is in the middle of an ocean desert. Besides the flora and fauna supported by the coral reefs there is little life in the nearby ocean. Our coral reefs are under attack by several forces. Dr. Jokiel surveyed several related to global warming. 

1) Coral Bleaching
2) Sea level rise
3) Ocean acidification (related to CO2 absorbed by ocean)
4) Changes to El Nino patterns
5) Increased and more violent storms 

As bad as all these things are, he pointed to increasing atmospheric CO2 as being the most important element in our coral's prognosis. He cited evidence that we are now at 380ppm (parts per million) of CO2 in the atmosphere, and that we are on a trajectory to reach 450ppm. That level conforms to a 2º Centigrade rise in the Earth's temperature.

A two degree rise in ocean temperature would be fatal to most coral in Hawaii. To add to the stress on coral reefs is the fate of an algae called crustose coralline that is threatened by climate change and acts as the adhesive that binds coral shells together in reef structures. In a range of 1-2ºC rise in temperature there may still be coral alive, but crustose corralline may be destroyed, thus dissolving the reef structure. This possibility alone is reason for targeting 350ppm as the target for atmospheric CO2.  

My Conclusion
After hearing these presentations, a picture emerged of a future Kauai with a much dryer climate, and little drinking water. A place with hardly any beaches and damaged coastal infrastructure. An island in the middle of an ocean desert with no coral reefs and the life they support. Action to be taken at the largest scale is to fight hard for the target of 350ppm of CO2, even if that means a de-industrialization of the world economy.

We must stop burning fossil fuels or live in hell. Locally we must be prepared to slowly switch over to agriculture in a dryer, warmer climate. We must reestablish fishponds and aquaculture that can supplement the losses we face in the ocean. We must develop further inland and at higher elevations without impinging on the forests we need for survival. We need to slow runoff, and the lowering of our aquifers.

When people complain about there not being jobs on Kauai, it's not for lack of work to be done. It's for a lack of the will to do it or reward it. See also: For a GoogleEarth flyover showing 1 meter sea riase on Kauai http://www.soest.hawaii.edu/coasts/sealevel/index.html