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2016 hottest year in Singapore, overall rainfall less than normal
Today Online 23 Mar 17;
SINGAPORE — Singapore experienced its hottest year on record last year as rainfall fell slightly below normal levels, the Meteorological Service Singapore (MSS) said in a report released on Thursday (March 23).
The annual mean temperature of 28.4°C last year was higher than the climatological average of 27.5°C (taken over the 1981-2010 base period). This breaks the previous joint record of 28.3°C set in 2015, 1998 and 1997.
As for annual rainfall, overall, the 1,956mm recorded last year measured below the climatological average of 2,166mm.
Last December, the MSS already gave an early indication that 2016 would be the hottest year since temperature records were collected in 1929.
Temperatures soared in the first half of last year due to the effects of a very strong El Nino phenomenon, giving rise to warmer and drier weather conditions in the South-east Asia region. El Nino gave way to La Nina in the second half of the year, resulting in wetter conditions.
New monthly records were also set last year, with January (28.3°C), April (29.4°C) and August (28.9°C) being the warmest months. The month of May was the second warmest May since May 1998, while December was the second warmest December after December 2015.
Last year also saw the driest March ever in Singapore, with a monthly rainfall total of 6.2mm recorded at Changi climate station.
However, the western parts of the island experienced well above normal rainfall in June and July, with the year’s highest monthly rainfall (434.4mm) recorded in July over Jurong.
In its Annual Climate Assessment Report 2016, the MSS also said that a relatively wet start of the South-west Monsoon was part of the reason why there were fewer and less severe occurrences of transboundary haze affecting the region last year compared to the year before.
“Singapore was affected by only one significant episode from 26 to 28 August 2016 when haze from fires in central Sumatra was blown in by the prevailing westerly winds. The 24-hr Pollutant Standards Index reached a high of 143 (in the unhealthy range) at 8am on 27 August 2016, before gradually returning to normal levels in the late afternoon on 28 August 2016,” the report said.
The MSS also pointed out that eight of Singapore’s 10 warmest years happened in the 21st century. All the 10 warmest years have occurred since 1997, consistent with ongoing global warming.
Worldwide, last year was also the warmest year on record, as recently confirmed by the World Meteorological Organisation, the MSS said.
The release of the report by the MSS is in conjunction with the World Meteorological Day, which is observed yearly on March 23.
EL NINO AND LA NINA
El Nino occurs every three to five years on average, when the sea surface tempareture in the eastern and central tropical Pacific Ocean is warmer than normal, causing disruptions to weather patterns globally. La Nina is the reverse of El Nino, when the sea surface temperature in the same parts of the Pacific is much cooler than normal.
2016 was warmest year on record for Singapore: MSS
Channel NewsAsia 23 Mar 17;
SINGAPORE: Last year was the warmest on record for Singapore, the Meteorological Service Singapore (MSS) announced on Thursday (Mar 23), breaking the previous joint record set in the years 2015, 1998 and 1997.
2016 saw an annual mean temperature of 28.4°C, exceeding the climatological average by 0.9°C, MSS stated in its Annual Climate Assessment Report.
Eight of Singapore’s 10 warmest years have occurred in the current 21st century, with all the 10 warmest years occurring since 1997, consistent with ongoing global warming, MSS said.
January, April and August set new records for being the warmest of each month in Singapore's history. In addition, May and December 2016 were the second warmest May (after May 1998) and December (after December 2015).
Based on Annual Climatological Report 2016, some temperature stations omitted due to incomplete dataset.
EL NINO A FACTOR
In addition to ongoing global warming, natural climate variability also played a major part in these record warm years, with all the years connected to El Nino events, said MSS.
A strong El Nino emerged in the second half of 2015 and started to decline in early 2016. According to MSS it had a significant impact on temperature and rainfall across Singapore and the surrounding region, which experienced hot and dry weather spells in March and April 2016.
El Nino is a recurring climate pattern caused by interactions between the atmosphere and the ocean in the tropical Pacific. During El Nino, the central-eastern equatorial Pacific Ocean is warmer than usual, leading to drier and warmer conditions especially during the June to October period over Southeast Asia.
The second half of 2017 also saw a high frequency of Sumatra squalls, which brought moderate to heavy thundery showers and gusty winds to Singapore, according to the MSS report.
El Nino gave way to its reverse, La Nina, in the second half of 2016, resulting in wetter conditions over the region, it added.
- CNA/nc
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Rare bid by tenants to conserve building
Melody Zaccheus, The Straits Times AsiaOne 23 Mar 17;
Most building conservation efforts in Singapore are led by the Urban Redevelopment Authority (URA), which decides what to add to the country's stable of 7,000-plus protected structures.
In a rare case, a group of heritage enthusiasts, including executives from a property company, banded together to have the building they rent - The Quadrant in Cecil Street - gazetted for conservation by the URA.
About $1 million of the company's money was spent restoring it. It started off as just another project for Homestead Group chief executive Low Jeng-tek, portfolio asset director Sue Ann Lim and design lead Sue Lynn Oliveiro, whose company specialises in refurbishing heritage properties for new uses.
As master tenants, they were sprucing up the dilapidated building in the Central Business District and turning it into a tech office complex after taking over from a childcare operator in 2012. They had signed a nine-year lease with the Singapore Land Authority (SLA).
Read also: Homeowner forced to move out after tenants skip rent for 3 years and refuse to leave Hougang flat
They soon began uncovering stories about the 1930s low-rise landmark's history and architectural merits, prompting them to question why it had yet to be protected.
Last month, Mr Low's former classmate, heritage enthusiast Gareth Lee, sent a letter to the URA proposing its conservation.
The letter by Mr Lee, 49, the vice-president and Asia-Pacific general counsel of an American healthcare company, described The Quadrant as an "art deco structure which sits at the gateway to Raffles Place and Marina Bay", and a "lone relic" of pre-WWll Singapore in an area dominated by skyscrapers.
The Homestead executives had shared their findings with him:
•The Quadrant had served as the South-east Asian headquarters of the Kwangtung Provincial Bank, which was used by immigrant Chinese to remit money, and its original banking hall layout and bank vault were still intact.
•It was set up by finance minister T.V. Soong of the Republic of China, brother-in-law of Chinese revolutionary Sun Yat Sen.
Read also: Experts want more say under heritage blueprint
Their year-long restoration also brought back to life its original iron-gate traction lift - one of the few remaining in Singapore.
Mr Low told The Straits Times: "Our lease expires in 2021. Our worry is that the historical and architecturally unique building could one day be torn down and replaced by a skyscraper, given the value of land in the district.
"While we are still the stewards of this property, while it is still in our care, we must do something to ensure it stays beyond this date."
A Facebook group, Conserve The Quadrant, has been set up.
Read also: Penang ups landed property threshold
Most ground-up efforts to conserve buildings are usually led by owners of private buildings under the URA's voluntary conservation scheme. A URA spokesman said there have been "a handful" of such cases over the last decade, including the Parochial House at St Joseph's Church in Victoria Street.
Independent conservation bids by non-owners are even rarer.
Experts whom the group contacted, including cultural geographer Lily Kong, expressed surprise that The Quadrant had yet to receive conservation status.
A possible reason is that a road reserve line runs across the building.
Professor Kong said the private sector stepping forward to propose its conservation would belie a nation coming of age "in which our values include pride in our history and heritage". She said: "As Singapore matures, it would be great not to rely only or largely on the Government for conservation. There is certainly a prima facie case for this building to undergo assessment."
Read also: Property expert cautions against stalling market
The URA said it welcomes the suggestion, adding however that as there are no immediate plans for the site, "the merits of conserving the building will be studied as part of the larger plans for the area".
As custodian of state properties, SLA has been opening up places with "heritage value and historical charm" to optimise their use, said chief executive Tan Boon Khai.
Mr Low said juxtaposing older heritage buildings with modern skyscrapers is an internationally proven "sure-fire way to attract creative techies like bees to honey".
He added: "Conserving The Quadrant will educate the public about our yesterdays, and also connect us to an innovative new tomorrow."
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MAS to offset cost of issuing green bonds with new grant scheme
Calvin Hui Channel NewsAsia 23 Mar 17;
SINGAPORE: The Monetary Authority of Singapore (MAS) will introduce a Green Bond Grant scheme this year to offset the cost of companies issuing sustainability-oriented bonds, Second Minister for Finance Lawrence Wong announced on Thursday (Mar 23).
Green bonds are debt instruments with proceeds earmarked for projects with environmental benefits, such as those to reduce greenhouse gas emissions.
Speaking at the Investment Management Association of Singapore’s 20th Anniversary conference, Mr Wong said the new grant comes as the central bank is looking to promote the development of a wider range of sustainability-oriented benchmarks, funds and products to cater to growing demand.
The global green bond market has grown rapidly over the years, reaching more than US$80 billion (S$112 billion) in 2016, the minister noted, adding that the market was starting to take off in Asia.
According to Mr Wong, MAS recognises that green bond issuers may have to bear additional costs as they engage external reviewers to ascertain their green bond status.
The Green Bond Grant scheme will be able to offset 100 per cent of the cost of obtaining an external review for green bonds for qualifying issuances, up to S$100,000 per issuance, he said.
Issuers will also be able to receive the grant multiple times. The funding period will take place between Jun 1 this year, and May 31, 2020.
Qualifying criteria states that the bond has to be issued and listed in Singapore, have a minimum size S$200 million and tenure of at least three years. The bond can be denominated in any currency.
While green bonds might incur higher costs with the need for an external review, PwC Singapore’s Asia-Pacific Asset and Wealth Management Leader Justin Ong said the focus of green bonds is not necessarily on higher returns, but on investment decisions that are environmentally sustainable.
“The world as I see it is starting to change. A lot of the investors today are much more focused around 'What am I putting my money in? Would I be prepared to forgo some returns to make sure that I am happy with the kind of structures and kind of policies the company is making?' And we are starting to see that to change.”
The introduction of this grant scheme has also been welcomed by industry watchers.
Calling it a “positive development” for Singapore’s capital markets, Tony Lewis, who is head of HSBC Securities Services, Singapore, said: “Green finance is a rapidly growing field, spurred on by consensus that more needs to be done to combat climate change. Encouraging more issuers to tap into the green bond market should help kick start interest in this asset class and foster the growth of green bonds’ issuance in Singapore.”
PwC Singapore’s Mr Ong agreed, saying events like haze and pollution in the Asia-Pacific has put the focus on sustainable development.
And while it is still early days, the development of the green bond market in Singapore will help strengthen Singapore’s position as a financial services hub, said Mr Ong. “I would say we are still taking baby steps. It’s a very new area around the world, but it’s a long-term thing and will build a strong foundation for our future.”
GOVT SEEKS FEEDBACK ON NEW CORPORATE STRUCTURE
Meanwhile, Mr Wong also announced the launch of a public consultation to gather feedback on a new corporate structure called the Singapore Variable Capital Company (S-VACC).
S-VACC seeks to complement existing corporate structures for investment funds and allow asset managers to further consolidate their operations in Singapore by domiciling more of their funds here, alongside their fund management activities, Mr Wong said.
“This will spur demand for fund servicing activities, such as accounting, legal, custody and tax in Singapore, hence creating more jobs in the broader professional services sector," the minister said.
According to MAS, there are three types of structures used by investment funds in Singapore, namely unit trusts, companies formed under the Companies Act and limited partnerships. The S-VACC seeks to complement these existing structures with one that is tailored for investment funds.
Mr Wong added that the new corporate structure would provide greater flexibility and cost efficiency to asset managers by allowing for both open-ended and close-ended fund structures. It also allows for investment across all asset classes and may be used by both retail and private funds.
By consolidating administrative functions at the umbrella fund level, asset managers can also harness economies of scale, Mr Wong said. “This means that sub-funds, with varying risk levels, different investment objectives and classes of investors can be housed under the same umbrella as a single legal entity,” he explained.
The public consultation will end on April 24, said MAS.
- CNA/mz
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Malaysia: Gua Musang hydroelectric projects to comprise 20k+ of flooded areas
JUNE MOH New Straits Times 23 Mar 17;
KUALA LUMPUR: The proposed Lebir Hydroelectric Power Development Project in Gua Musang, Kelantan, will have a total flooded area of 15,400 hectares, Minister of Energy, Green Technology and Water, Datuk Seri Panglima Maximus Johnity Ongkili said today.
Ongkili (BN-Kota Marudu) said the total area to be flooded is based on Tenaga Nasional Bhd (TNB)’s feasibility study.
“The government is still studying the proposal to build a dual-function Lebir dam, which will act as a flood mitigation project, as well as an electricity generator,” he told the Dewan Rakyat today.
Another dam, the Nenggiri Hydroelectric Power Development Project, which is located in the same district, will have a total flooded area of 5,834 hectares.
“The feasibility study on this project was conducted by TNB. At this juncture, TNB is conducting the Environmental Impact Assessment (EIA), design and engineering studies of the dam,” he said.
Ongkili was replying to questions from Ahmad Marzuk Shaary (PAS-Bachok) on latest studies on the Lebir and Nenggiri dam projects, and the total area to be flooded for the two projects.
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Malaysia: Check impact of shrimp farms on ecology
The Star 23 Mar 17;
GEORGE TOWN: Sahabat Alam Malaysia (SAM) wants the state Fisheries Department to study the pollution impact of aquaculture ponds, especially those at shrimp farms, on the west side of Penang island and publicly disclose the findings.
It is concerned that the state’s mangrove forests and fisheries resources would be destroyed if more shrimp farms are constructed without a thorough study of their impact on the environment.
“Our recent survey found that the ditches on the west side of the island were filled with sludge and debris from residential areas and aquaculture ponds. The smelly water is black and frothy,” said SAM president S.M. Mohamed Idris.
He said there were several drains and canals in the area through which the black water flows directly into the sea.
“This pollution threatens marine life and the livelihood of about 2,000 fishermen in Kuala Sungai Pinang, Pantai Acheh, Kuala Sungai Burung and Pulau Betong who have complained of smaller catches of fish, shrimp, crabs, mussels and clams.”
Mohamed Idris said Consumers Association of Penang and the affected fishermen had complained to the state government and the Penang Island City Council but claimed no action had been taken.
“SAM believes that if this pollution is not taken seriously and allowed to continue, not only will the environment here be destroyed in twenty years but the fish will die off, causing the fishermen to lose their livelihood.”
Local Government Committee chairman Chow Kon Yeow said he would seek more information from the state Drainage and Irrigation Department before commenting.
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Record-high sea levels along China’s coast ‘could spell disaster’
State Oceanic Administration warns of increased damage from flooding and stronger typhoons as oceans rise
Kinling Lo South China Morning Post 23 Mar 17;
Scientists have warned of rising risks from natural disasters such as storm surges and typhoons, with record high sea levels reported along China’s coast.
In its annual reports on the state of the nation’s marine environment, the State Oceanic Administration (SOA) said on Wednesday that in 2016, the average sea level was 82mm higher than that from 1993 to 2001. Last year’s figure was also 38mm above the 2015 average.
The rising sea level would aggravate the damage caused by natural disasters, which the SOA said cost 5 billion yuan (US$726 million) last year and left 60 people dead or missing.
Using the average between 1993 and 2011 as a base, the reports said the coasts of Shanghai, Zhejiang and Fujian last year recorded their highest increase in sea level, up more than 100mm over the benchmark.
In Yancheng, Jiangsu province, the rising sea level aggravated coastal erosion, with the water line moving as much as 59 metres further inland last year, the reports said.
While in many cases climate change and El Nino and La Nina events were to blame for the rise in sea levels, subsidence was also a big factor the northern city of Tianjin. The SOA estimated the port city’s sea level would rise by 80 to 180 mm in 30 years.
Rising sea levels also aggravated storm surges, erosion and salt tides in Guangdong.
The SOA said the average rise from 1980 to 2016 was 3.2mm per year. Nasa has reported a global rise of 3.2-3.6 mm per year, based on satellite observations.
“A rise of a few millimetres may seem small, but if you think about how big the ocean is, the changes make a huge difference when sea water hits land,” said Professor Huang Gang of the Chinese Academy of Sciences’ Institute of Atmospheric Physics.
Huang led a research project in 2015 that predicted water levels would rise by as much as 1.2 metres in the Pearl River Delta by the end of this century. This would have a catastrophic impact, such as flooding low-lying areas like Hong Kong and Macau.
“The adverse impacts could come earlier if sea levels rise faster,” he said.
SOA reports in recent years have warned that the thermal expansion of seawater and glacial melting due to climate change were contributing to an accelerating rise in global sea levels.
On top of this global trend, Huang said pollution in China’s coastal areas was also contributing to a rise in the water level.
Last year, signatories to the Paris Agreement on climate change vowed to limit the rise in the average global temperature to below 2 degrees Celsius. China signed the deal with 191 other states and the European Union.
But Liu Zhonghui, associate professor in earth sciences at the University of Hong Kong, was not optimistic about the target.
“Past global efforts to cut greenhouse emissions have not been too successful,” Liu said. “The rising trend in sea levels, the effect of global warming, will continue in the foreseeable future.”
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South China Sea: Shock mass coral die-off in Asia sounds alarm for world’s reefs
Alice Klein New Scientist 23 Mar 17;
It’s even worse than we thought. An unexpected coral bleaching event in the South China Sea shows that reefs can heat up substantially more than the surrounding ocean, making them more vulnerable to climate change.
The finding suggests that efforts to limit global warming to 2 °C under the Paris Agreement may not be sufficient to save the world’s tropical reefs.
In June 2015, the South China Sea warmed by 2 °C in response to a normal El Niño weather pattern. The moderate temperature rise was not expected to cause significant coral damage.
However, at Dongsha Atoll in the northern part of the sea, the sea surface temperature soared to 6 °C above average, killing 40 per cent of the coral.
This temperature blow-out occurred because the atoll’s shallow water was able to heat up more than the surrounding ocean, research led by Thomas DeCarlo at the University of Western Australia shows. This amplified the El Niño effect.
In addition, unusually weak winds during the same period slowed the spread of heat into the surrounding ocean, so that it became trapped within the atoll.
“Ocean temperatures are already warming due to climate change,” says DeCarlo. “But what we’ve shown is that on top of that, local weather anomalies or processes like reduced wind can drive reef temperatures even higher,” he says. “That compounds the risk that corals are facing.”
The findings fit with emerging research from other coral reefs, says Bill Leggat at James Cook University in Townsville, Australia. “The evidence suggests that we’re going to get these local conditions pushing corals above bleaching levels a lot more often.”
Triple threat
Sea surface temperatures around the world have been increasing by an average of 0.07 °C per decade over the last century due to human-made climate change. This has increased the risk that El Niño and local weather anomalies will tip reef temperatures into the danger zone.
Tropical coral reefs are sensitive to small temperature anomalies – as little as 1 °C, DeCarlo says. Warmer waters strip away the colourful photosynthesising algae that nourish corals, leading to bleaching and often death.
To examine whether previous El Niño events have caused bleaching at Dongsha Atoll, the team analysed 22 coral skeleton cores. They looked for stress bands along the cores indicative of earlier bleaching events.
The results showed that less than half the coral was bleached during El Niño events in 1983, 1998 and 2007. But during the 2015 El Niño, 100 per cent of the coral was bleached. This implies that the 2015 bleaching event was the most severe to hit Dongsha Atoll in at least the past 40 years, and possibly much longer, DeCarlo says.
Most future projections for coral reefs in a 2°C global warming scenario only take into account background ocean warming, rather than local weather effects on reefs, says DeCarlo. “They may be overly optimistic.”
“The only hope now is to minimise carbon dioxide emissions as much as possible and try to protect reefs as best as we can on a local scale,” says Leggat.
'Devastating' coral loss in South China Sea - scientists
Helen Briggs BBC News 24 Mar 17;
Scientists are warning of another "devastating" loss of coral due to a spike in sea temperatures.
They say 40% of coral has died at the Dongsha Atoll in the South China Sea.
Nothing as severe has happened on Dongsha for at least 40 years, according to experts.
Anne Cohen of Woods Hole Oceanographic Institution in Massachusetts, US, said the high water temperatures of 2015/16 were devastating for reef systems globally, including Dongsha.
Coral bleaching - where corals turn white and may die - was the worst on record for Australia's iconic Great Barrier Reef in 2016.
The barrier reef has absorbed a lot of the attention, but other reefs around the world were also severely affected, said Dr Cohen.
"The 2015/2016 El Nino was devastating for reef systems in other parts of the world as well, including Dongsha Atoll and reefs in the central Pacific, where some of the most pristine coral reefs are located and of course, the US Pacific Remote Marine National Monument," she said. "We observed devastating bleaching in that area as well."
Only last week, scientists published observations of three major die-offs of coral at the Great Barrier Reef in 2016, 2002 and 1998.
They concluded that the only way to preserve the world's coral reefs is to take drastic action to reduce global warming.
The study of the Dongsha Atoll, reported in the journal, Scientific Reports, echoes this finding.
"Based on what we observed on Dongsha, a 2 degree cap on ocean warming may not be enough to save coral reefs," Dr Cohen told BBC News.
"This is because coral reefs are shallow water ecosystems and a tweak in the local weather can turn that 2 degrees Celsius into a 6 degrees Celsius warming."
The Dongsha Atoll, located in the South China Sea, near south-eastern China and the Philippines, is rich in marine life and is regarded as one of the world's most important coral reefs.
The researchers said on its own, a 2 degrees Celsius rise in temperatures was unlikely to cause widespread damage to coral reefs in the region.
But, a high-pressure system caused temperatures to spike to 6 degrees, leading to the death of 40% of coral over the course of six weeks.
They argue that predictions of the future of coral reefs may be "overly optimistic" for some reefs in shallow water.
Bleaching happens when high water temperatures cause corals to expel the algae they depend upon.
The Australian government confirmed in March that widespread coral bleaching is happening on the Great Barrier Reef for the fourth time in history.
Corals die as global warming collides with local weather in the South China Sea
Woods Hole Oceanographic Institution Science Daily 23 Mar 17;
In the South China Sea, a 2°C rise in the sea surface temperature in June 2015 was amplified to produce a 6°C rise on Dongsha Atoll, a shallow coral reef ecosystem, killing approximately 40 percent of the resident coral community within weeks, according to a study.
In the South China Sea, a 2°C rise in the sea surface temperature in June 2015 was amplified to produce a 6°C rise on Dongsha Atoll, a shallow coral reef ecosystem, killing approximately 40 percent of the resident coral community within weeks, according to a study published in Scientific Reports this week.
Wind and waves churn the sea, flushing shallow-water coral reefs with seawater from the open ocean to help them stay cool. But according to new research from the Woods Hole Oceanographic Institution (WHOI), when the weather turns still and these natural cooling mechanisms subside, just a few degrees of ocean warming can prove lethal to the corals that live there.
Scientists at WHOI studied this phenomenon in June 2015 while conducting research on Dongsha Atoll, an almost perfectly circular coral reef in the remote South China Sea. The findings, published in the March 24, 2017 issue of the journal Scientific Reports, highlight the devastation caused when global-scale ocean warming interacts with short-lived weather anomalies, and adds urgency to the question of how reefs will fare through the end of this century.
"Dongsha Atoll is typically hit with tropical storms and strong winds in June, which keep the corals as cool as the open ocean," said Tom DeCarlo, lead author of the study and a then-graduate student in the MIT-WHOI Joint Program in Oceanography. "But in 2015, the weather in June was exceptionally calm -- at one point, there was basically no wind and no waves. This had an amplifying effect on the water temperatures, which were already feeling the heat from global warming and El Niño. The whole reef became a giant swimming pool that just sat there and baked in the sun."
According the DeCarlo, who is now a scientist with the University of Western Australia, it only took a few days of calm winds and waves before the reef lost its supply of cooler water from the open ocean. "We saw water temperatures surge to 36 °C (97 °F) -- a full 6° C above normal summertime temperatures. This caused 100% of the corals to bleach, and 40% of them died," he said.
Gone and back again
DeCarlo, WHOI scientist Anne Cohen, and dive master Pat Lohmann, witnessed the start of the mass die-off on the last day of their month-long field visit to Dongsha. They had just finished up an ecological survey of coral cover on the reef, and before heading home, jumped in the water to retrieve instruments they use to monitor water temperature, pH and currents. "That's when we saw that all the corals had turned white," said DeCarlo. "We had to catch our flights the next day, but the situation looked dire so Anne sent us back out to the site within a few weeks.
According to Cohen, the lead principal investigator on the project, the timing was remarkable given they were still on site when the bleaching started. "It's quite uncommon to be out there in such a remote place as a massive bleaching event is actually happening," said Cohen. "From Tom's surveys, we knew what the healthy reef looked like just before the bleaching, so we could make a direct comparison with the post-bleaching data to assess the effects of the warming."
Upon their return, the scientists boated back out to the reef and saw a green tint shimmering through the water -- a possible sign that the corals made it through the bleaching event and were returning to a normal state. But when they dove in, they realized what they had seen was actually green turf algae covering dead corals. "This was the fastest-calcifying reef we've ever studied," said DeCarlo. "So we thought it would have shown resiliency. But everything had come crashing down in the space of a few weeks."
Cooling system shutdown
The team suspected the amplified warming was due to the weather lull, but they couldn't automatically rule out the possibility that fewer clouds and more sunlight in 2015 versus previous years had caused the event. To test this hypothesis, DeCarlo and co-author Kristen Davis, using data recorded by instruments deployed on the reef, conducted a number of "heat budget" calculations to hone in on the specific factors that drove the extreme heating.
"We saw that air-to-sea heating mechanisms like sunlight and air temperature had remained nearly constant throughout June, but the wind- and wave-driven currents pushing in cooler offshore water were essentially turned off for a few days. This was the big change that caused the water temperatures to spike on the reef, so our hypothesis was correct -- the unusually calm weather pattern was the primary culprit," said DeCarlo.
Scanning history
Water temperatures stabilized in early July as the winds and waves finally kicked up. But the widespread damage had already been done. Given the magnitude of the event, the scientists wanted to know if this reef had experienced similar temperature extremes in the past, and if so, whether the corals recovered. According to Cohen, however, few historical bleaching data existed for the region.
"This is a super-remote place that takes two hours to get to by plane from mainland Taiwan," she said. There were unpublished accounts of bleaching in 1997, but the severity and extent of that event were not quantified.
Without precise historical records, the team drilled core samples from corals living on the reef and used Computed Tomography (CT) scans to look for signals of thermal stress in the past. The scans, which look like an x-rayed mop handle, reveal annual rings or "bands" of varying densities in the coral's skeleton.
"These bands are like a history book for coral reefs, allowing you to count back in time to specific years and events," said Cohen, who attributes her lab's unique "paleo perspective" to her background in paleo-oceanography. "The brighter, high-density bands, which we call 'stress bands,' are signatures of long and intense bleaching events. Based on cores we scanned, it appears there had been only three previous bleaching events between 1983 and 2015, each of which happened in El Niño years. But we detected very few stress bands in the cores, so while there had been bleaching, these events were not nearly as severe as 2015."
Interpreting the CT scan data, DeCarlo says many corals that had bleached in the past appear to have recovered. "The skeletal records show that less than 50 percent of the colonies had bleached during these historical events, which is a stark contrast to the 100 percent bleaching we saw in 2015. This suggests that the area had not seen thermal stress this extreme in the last forty years at least -- maybe even in the last 100 years."
21st century reef
The study highlights the consequences for shallow-water coral reefs when global warming intersects with short-lived weather anomalies. But the scientists say their observations also suggest the possibility that climate model projections may underestimate what some coral reefs will experience as the ocean continues to warm over this century.
"The current global climate models and prognosis for reefs are based on a 2 °C warming scenario for the open ocean," said DeCarlo. "But these projections usually don't account for the kind of regional and local weather anomalies we saw at Dongsha. When you have weather amplification events superimposed on top of carbon dioxide-driven ocean warming, that's when things can get really bad for corals. Models based on open-ocean warming already paint a dire picture for coral reefs, but the scary reality is that they may be too optimistic for many shallow reefs."
"Projections based on open-ocean temperatures may not be 100% relevant to these shallow-water environments, where many coral communities live," Cohen added. "It's possible that coral reefs are in much more immediate danger than we have anticipated. When global and regional anomalies align, a seemingly-mild two-degree warming could be more like six degrees."
Journal Reference:
Thomas M. DeCarlo, Anne L. Cohen, George T. F. Wong, Kristen A. Davis, Pat Lohmann, Keryea Soong. Mass coral mortality under local amplification of 2 °C ocean warming. Scientific Reports, 2017; 7: 44586 DOI: 10.1038/srep44586
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