Inaugural Coral Reef Watch

29 10 2015

Dale C. S. Destin |

The Antigua and Barbuda Meteorological Service (ABMS) through its climate section (ABMS CliSec) has started to issue bulletins on coral bleaching in Antigua and Barbuda. This is being done with technical support of the U.S. NOAA Coral Reef Watch and Caribbean Climate Outlook Forum (CariCOF).

We are calling the bulletin – Antigua and Barbuda Coral Reef Watch or ABC Reef Watch. The aim is to provide early warning of coral reef bleaching, to raise awareness of the value of these reefs to our existence and to help in the promotion of their conservation.

We will provide weekly updates (by each Wednesday) until the end of the bleaching season, which may go until December this year. Thereafter, we will provide monthly bulletins (by each first Wednesday), until the next bleaching season – July to November, when weekly updates will resume.

For future updates, you may visit our climate page or please subscribe here.

Without further ado and a sense of pride, we are pleased to present you with our inaugural Antigua and Barbuda Coral (ABC) Reef Watch: http://antiguamet.com/Climate/ABCRW/2015/ABCReefWatch_Vol1_Issue1_Oct_2015.pdf

Please feel free to provide feedback.





Amen! Antigua’s Surface Water Catchments to be Cleaned

26 10 2015

Dale C. S. Destin |

Amen! The Government of Antigua and Barbuda (GOAB) through the Antigua Public Utilities Authority (APUA) has finally decided to do what the masses, for decades, have been calling, if not clamouring for– the cleaning of the country’s surface water catchments.

Potworks Dam - Aug 1, 2015

Potworks Dam – Aug 1, 2015 | Courtesy Karen Corbin, Humane Society

Will cleaning the catchments be enough to ensure our water security, especially in light of climate variability and change? What else could be done to reduce our water insecurity? I will be sharing my thoughts on these subjects over a series of blogs. In this first one, I will focus on the potential impact of climate variability and change on freshwater resources in Antigua”. This will be followed by adaptation measures, perhaps split into parts.

Unlike most other resources, there is simply no substitute for water. Although there is a lot of it surrounding us, there are limited amounts on the island.

Limitation of freshwater has for a very long time been a major issue for Antigua; the problem dates back to, at least, the British colonial times, when there were frequent crop failures due to insufficient rainfall.  In modern times, we have had the misfortune of having to import water from Dominica in 1984.

The program announced by the GOAB, through its Chief of Staff, would see the removal of overgrown vegetation and built-up silt from catchments, which have basically been left unmanaged from inception.

Bethesda Dam, July 31, 2015 | Courtesy Karen Corbin, Humane Society

Bethesda Dam, July 31, 2015 | Courtesy Karen Corbin, Humane Society

Climate Variability and Change and Water Resources

Notwithstanding our relatively low rainfall, on average, I believe we currently get enough to thrive. The real challenge is collecting enough of it to sustain our socio-economic growth. However, in the long run, climate variability and change are projected to worsen our water scarcity. According to the last IPCC report, we are likely to have reduced rainfall, which will be exacerbated by increased evaporation rates caused by rising temperature.

Antigua’s surface water resources will be the most impacted by climate variability and change. Our main surface water storage, Potworks Reservoir, constitutes about 83% of total surface storage capacity. The reservoir has a maximum capacity of about 4.5 million cubic metres (m3)(1 billion imperial gallons). The structure has extensive shallow zones with an average dept of around 2.4 metres (8 feet), making it almost ideally vulnerable to high evaporation rates.

At present, Potworks alone loses around 9610 m3 (2.1 million imperial gallons – MIG) of water daily. Antigua’s daily water requirement is around 36369 m3 (8 MIG). This means, every four days we lose one day’s supply of water. One of the main drivers of evaporation is temperature. Thus, as our temperature continues to rise, we will experience greater water losses to the atmosphere.

The amount of water vapour the atmosphere can hold changes exponentially with temperature, as expressed by the Clausius-Clapeyron equation, and typically, there is a 7% change in the water holding capacity of the atmosphere per change in degree Celsius.

Although not as vulnerable to climate variability and change, ground water resources are also at risk on. There are about 56 active wells producing approximately 4546 m3 of water daily (1 MIG) and of depth ranging 1-50 metres (3-165 ft). These are clearly mostly wells which tap into unconfined aquifers that are relatively close to the surface of the ground; thus, they are exposed to the changing climate.

Confined, deeper wells would be more protected. Thus, for particularly unconfined and relative shallow aquifers, projected reduced rainfall and increased evapotranspiration due to climate variability and change will have depleting impact on groundwater sources.

Research shows that aquifer recharge is very sensitive to precipitation changes; a 15% reduction of rainfall could result in 40-50% reduction in the recharge of an aquifer. Added to that, in Antigua, the rainfall could decline by as much as 30% by 2100.

With the global climate warming and ice melting, sea level rise will exacerbate dwindling freshwater resources. As the sea rises, salt water will intrude further inland and contaminate aquifers, especially those relatively close to low-lying coastal areas.

Already, wells have been capped due to saltwater intrusion and others are likely to be capped going forward. A rise of a metre in sea level could reduce the land size of Antigua by only 1% but have a huge impact on water resources.

Based on the latest Inter-governmental Panel on Climate Change (IPCC) assessment report – AR5, it is very unclear as to how climate change will affect extreme precipitation events and droughts in Antigua, if at all. Data from the Antigua and Barbuda Meteorological Service Climate Section suggest that there is no trend with respect to extreme precipitation events and further work needs to be done on drought frequencies. However, increases in either will have negative impacts on water resources, especially with respect to quantity and quality.

There is no doubt that the government is doing the right thing by embarking on the cleaning of our surface catchments. Coping with climate variability and change will prove extremely challenging for Antigua. Tourism is the main driver of the economy and adequate water is need for its growth and sustainability.

The change of the global climate will likely have a net negative impact on all endeavours on the island, directly and indirectly. Water, the most vital resource to life, is projected to decline due to climate change. Models are projecting as much as 30% reduction of annual rainfall and contamination of coastal aquifers by saltwater intrusion due to sea level rise. Increased evaporation driven by global warming will adversely affect water storage in reservoirs and, to a lesser extent, aquifers.

Notwithstanding the challenges, the island is not without options to adapt. The next blog, on this subject, will explore some of these options.





Widespread Coral Reef Bleaching for Antigua and Barbuda

13 10 2015

Dale C. S. Destin |

The highest coral bleaching alert level is forecast for Antigua and Barbuda and much of the Caribbean as a part of the third ever global coral bleaching event. Alert level 2 has been issued for our coral reefs.  This means that our coral reefs are expected to undergo widespread bleaching with a significant amount possibly dying.

Credit: NOAA Coral Reef Watch

Credit: NOAA Coral Reef Watch

The bleaching in our neck of the woods is due mainly to the warming of the Atlantic Ocean which was brought on by persistent light winds or negative North Atlantic Oscillation. Meanwhile, the Pacific bleaching is largely due to El Nino. Global warming is most likely playing an underlying role.

Corals start to bleach when the sea surface temperature (SST) exceeds the maximum monthly mean SST by 1 °C (1.8 °F). This cause corals to spew their algae, which they need to feed themselves. For our area, the bleaching threshold is 30.0 °C (86 °F). Currently, SST around Antigua is about 30.0 °C (86 °F) and rising.

Credit: NOAA Coral Reef Watch

Credit: NOAA Coral Reef Watch – http://coralreefwatch.noaa.gov

In the future, climate change, force by global warming, is expected to play a lead role in coral bleaching. According to the Inter-governmental Panel on Climate Change, warming in the top 100 metres of the ocean will rise a further 0.6 to 2 °C by the end of the 21st century. Greater warming is anticipated at the surface of the ocean. This could result in mass bleaching events becoming common place.

These images, taken in American Samoa, show the devastation caused by coral bleaching between December 2014 and February 2015 (Credit: XL Catlin Seaview Survey)

These images, taken in American Samoa, show the devastation caused by coral bleaching between December 2014 and February 2015 (Credit: XL Catlin Seaview Survey)

The bleaching has negative implications for our tourism industry. Coral reefs are a major source of sand for tropical beaches such as our 365 white sandy beaches, which are our main tourism drawing card. Degraded coral reefs could result in a decline in the replenishment of sand on our beaches and eventually reduce our islands’ attractiveness to tourists.

Additionally, many persons come to our shores to snorkel and enjoy the spectacular underwater beauty provided by coral reefs and the sea life they attract. Every coral bleached or killed reduces our drawing power of those tourists interested in this kind of scenery.

The bleaching also has negative implications for our food security, livelihoods, coastal protection, ocean acidification and climate change.

According to Professor Ove Hoegh-Guldberg of the University of Queensland, who was quoted in a recent BBC news article, “just like in 1998 and 2010, we’re observing bleaching on a global scale, which will cause massive loss of corals. With people relying on fisheries and reefs for sustenance, the repercussions could be potentially disastrous.”

Coral reefs are vitally important to Antigua and Barbuda and the rest of the world. They perform a long list of functions for us all. Chief among them is the role they play in the food chain. Corals serve as sanctuary for countless different species of fish. These reefs serve as homes for fish, without which they would be homeless with no place to safely have their babies.

The role played by coral reefs contributes in no small way to reef fish and mollusc, feeding as many as 40 million people annually.

Another important role coral reefs play is that of protecting our coastlines. For regions like ours that are visited by tropical cyclones (the generic term for tropical depressions, tropical storms and hurricanes) on an annual basis, coral reefs serve as a natural and vital protection against storm surge, strong currents and large waves by slowing down the water before it reaches the coastlines.

Coral reefs also play a very important role in the carbon cycle. They convert carbon dioxide (CO2) into limestone shell. Their absence would result in a rapid increase in CO2, which would eventually affect all living things on earth.

Generally, bleached corals end up dying. If they survive, their recovery can be very slow, taking decades.

The truth is, there isn’t a lot that we can do to mitigate a given bleaching event. However, systems could be put in place to keep our corals as healthy as possible by reducing pollution, coastal runoff and over fishing. Such measures would raise and keep corals at optimal health, which would improve their chances of surviving bleaching.

In the final analysis, if we are to continue to enjoy the products and services of our coral reefs, the world would have to make better than ambitious cuts to their CO2 emissions, the main cause of global warming and climate change. So far, the proposed cuts to emissions are still very far from what is required to keep global surface temperature below the level that will perhaps prevent the extinction of corals and dangerous climate change.

We will continue to follow this issue over the upcoming months and keep you informed.





Historic Heat for Antigua

6 10 2015

Dale C. S. Destin |

Historic heat has been taking place across most of Antigua over the past six days. From since last Wednesday (September 30), the mean maximum temperature at the V.C. Bird International Airport (VCBIA) has been 33.3 °C (92.3 °F). The highest for the period is 34.6 °C (94.3 °F) and the lowest is 32.2 °C (90.0 °F).

At the VCBIA, there has not been such a streak of high temperatures for, at least, the last 45 years. Since Wednesday, we have recorded three of the top six warmest temperatures on record: 34.6 °C– the second highest, 34.0 °C (93.2 °F)–the fifth highest and 33.9 °C (93.0 °F)–the sixth highest. The highs for the other days are now the highest relative to the given days.

Top10HottestDays

Contributing significantly to this extraordinary, oppressive heat of the past week are the light winds and relative humidity. When these are factored in with the temperature, the peak heat index or feel-like-temperature for each day was around 38 °C (100 °F). On Sunday, the heat index peaked at 40 °C or 104 °F. If you were out in the direct sunshine, the temperature could have felt as high as 43 °C (110 °F)

Today, we reached the threshold for a heatwave to be declared–at least six consecutive days with the maximum temperature in the top 10% of the base period of 1971-2010 for the given days.

The heatwave will likely come to an end by this Wednesday. However, it’s likely that temperatures will remain above normal for the coming months, as the tropical North Atlantic continues to warm above normal. Our outlooks are calling for higher than normal mean, maximum and minimum temperatures for the next six months.

This is the second heatwave for the year. The other took place April 25-30.

Residents need to be heat-wise so as to avoid the potential harm of a heatwave or above normal warmth. Residents are urged to take it easy during strenuous activities from around midmorning to midafternoon, as well as drink plenty of water. That is especially true for the elderly, children and those sensitive to the heat.

Protection against ultraviolet (UV) radiation to prevent sunburn is also highly recommended. The UV index is generally high all-year-round in our area, especially during days of low cloud coverage.

We will continue to monitor the situation and keep you informed. Live updates can be had from our twitter and facebook accounts.








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