Coral Reef Death ..

CORAL REEF DEATH LINKED TO TROPICAL
WILDFIRES IN INDONESIA DURING THE 1997
INDIAN OCEAN DIPOLE

N.J. Abram (1), M.K. Gagan (1), J. Chappell (1),
M.T. McCulloch (1), W.S. Hantoro (2)

The coral reefs of the Mentawai Islands, Indonesia, experienced catastrophic mortality of close to 100% of the coral and the fish during the 1997 Indian Ocean Dipole (IOD) upwelling event. The link between elevated sea surface temperatures (SST) and coral death is now well known, however the unanticipated Mentawai reef mortality coincided with anomalously cool SSTs and a giant red tide. Ocean productivity in the Indonesian region is generally proportional to the strength of upwelling; therefore the severity of the 1997 Mentawai reef death raises the question of whether the magnitude of the IOD upwelling and red tide during 1997 was unprecedented. Here we examine the tolerance of Mentawai corals to IOD upwelling events over the past 6,300 years using coral skeletal growth and palaeothermometry. High-resolution coral Sr/Ca and 18O reconstructions of SST reveal pre-historic IOD cold anomalies of up to 5.8C.

The magnitudes of these events exceed the strong 1997 IOD upwelling by as much as 1.9C, yet we find no evidence of past coral mortality. From these results it seems that the intensity of the 1997 Mentawai red tide was much greater than expected based on the magnitude of IOD upwelling alone. This implies that an additional source of nutrients must have supported the catastrophic red tide and we propose that these nutrients were provided by the 1997 Indonesian wildfires. These fires were the worst in south-east Asian history and were the combined results of land clearing, past forest disturbance and intense drought driven by the 1997 El Niño-Southern Oscillation and Indian Ocean Dipole events. Using mass balance calculations we show that ironfertilisation of the upwelled nutrient-enriched water by atmospheric fallout from the 1997 wildfires was sufficient to produce the extraordinary red tide, ultimately leading to the unprecedented death of the Mentawai reefs. These findings highlight the escalating phenomenon of tropical wildfire as a potential new threat to coastal marine ecosystems.

download full text.pdf

(1) Research School of Earth Sciences, The Australian National University, Canberra ACT 0200, Australia, (2) Research and Development Center for Geotechnology, Indonesian Institute of Sciences, Bandung 40135, Indonesia.

more.. »

The Return of EL Niño

Will Warm Water Wreak Havoc When Winds Won’t Blow?

Well, it looks like the next El Niño is coming. Right now many scientists are observing warming over the Tropical Pacific, and this has led to predictions of the next El Niño. El Niño is known to scientists as the El Niño-Southern Oscillation, or ENSO, and is a complicated chain of events that begins in the Pacific Ocean and then spreads to affect the weather around the entire world. What is the El-Niño Southern Oscillation, you ask? The El-Niño Southern Oscillation is the result of a cyclic warming and cooling of the surface ocean of the central and eastern Pacific.

In normal, non-El Niño conditions the central and eastern Pacific region of the ocean is normally colder than its equatorial location would suggest. This condition exists because of the influence of trade winds blowing to the west, a cold ocean current flowing up the coast of Chile, and upwelling of cold deep water off the coast of Peru. The trade winds blow toward the west across the tropical Pacific and these winds pile up warm surface water in the west Pacific. The sea-surface temperatures are much colder near South America because of an upwelling of cold water from deeper levels. This cold water is extremely nutrient rich, leading to high levels of primary productivity, a rich ecosystem, and major fisheries off the coast of Peru.

During an El Niño event, the trade winds weaken in the central and western Pacific for unknown reasons. This weakening causes western Pacific waters to cool, and a warming in the eastern Pacific. The warm, still surface waters in the east Pacific reduce the efficiency of the cold nutrient-rich upwelling, which results in an even larger increase in sea surface temperatures and a dramatic decline in productivity that severely impacts marine life and commercial fisheries in this area. The warming waters in the east Pacific cause huge thunderstorms and floods in the Peru area, while the cooler water temperatures in the west Pacific cause problems such as droughts in Indonesia and Australia.

Download Full Text.pdf

more.. »

The Indonesian Throughflow .....

The Indonesian Throughflow and the Global Climate System

Niklas Schneider

Climate Research Division, Scripps Institution of Oceanography, University of California,
San Diego, La Jolla, California

ABSTRACT

The role of the Indonesian Throughflow in the global climate system is investigated with a coupled ocean–atmosphere model by contrasting simulations with realistic throughflow and closed Indonesian passages.

The Indonesian Throughflow affects the oceanic circulation and thermocline depth around Australia and in the Indian Ocean as described in previous studies and explained by Sverdrup transports. An open throughflow thereby increases surface temperatures in the eastern Indian ocean, reduces temperatures in the equatorial Pacific, and shifts the warm pool and centers of deep convection in the atmosphere to the west. This control on sea surface temperature and deep convection affects atmospheric pressure in the entire Tropics and, via atmospheric teleconnections, in the midlatitudes. As a result, surface wind stress in the entire Tropics changes and meridional and zonal gradients of the tropical thermocline and associated currents increase in the Pacific and decrease in the Indian Ocean. The response includes an acceleration of the equatorial undercurrent in the Pacific, and a deceleration in the Indian Ocean. Thus the Indonesian Throughflow exerts significant control over the global climate in general and the tropical climate in particular.

Changes of surface fluxes in the Pacific warm pool region are consistent with the notion that shading by clouds, rather than increases of evaporation, limit highest surface temperatures in the open ocean of the western Pacific. In the marginal seas of the Pacific and in the Indian Ocean no such relationship is found. The feedback of the throughflow transport and its wind forcing is negative and suggests that this interplay cannot excite growing solution or lead to self-sustained oscillations of the ocean–atmosphere system. (full text)

more.. »

El Nino, who are you ...?

When the 1997 Indonesian fires broke out in mid-May of that year, no one took too much notice, as it was the beginning of the dry season. When the monsoons that carried precious rain to douse the flames and for crop growing did not arrive, the fires soon burned out of control into firestorms. The burning was most severe in East Kalimantan, a section of Indonesian part of Borneo, and the island of Sumatra, where an estimated total of 10,000,000 hectares was either totally burned or badly ravaged by the fires. Haze and smoke from the fires spread across Indonesia and Southeast Asia. At its worst the haze spread halfway across the Indian Ocean to the Maldives, north to the Philippines and Thailand, east to Papua New Guinea, and across northern Australia (Appendix #1). The widespread haze caused numerous health problems, affecting approximately 70 million people and causing 20 million of them to become sick. When neighboring countries complained about the deadly haze, President Suharto made a rare public apology, referring to the poisonous haze from the fires as "an act of God."2 The latest estimate of the damages of the fires was about US$4.5 billion, although when added with the value of lost timber and crops, this total skyrocketed to almost $9 billion. As further analyses of the fire's damages are being conducted, this estimate might rise. But most of the costs were probably impossible to calculate, as the damage the fires and resulting haze had on the environment and ecosystem were priceless and irreplaceable. The new Environmental Minister Juwono Sudarsono under the new President B.J. Habibie estimated that it might cost $2 billion to effectively respond to the fires.3

an image of normal ocean temperature

an image of el nino

Global map of: 1) normal ocean temperature, 2) el nino

The normal fires and the haze from it were significantly enhanced by El Nino, a weather phenomenon where the abnormally warm sea surface temperatures cause global weather patterns to change, resulting in abnormal weather effects around the world. In Indonesia, El Nino caused a drought because the monsoon season was pushed back from September to mid-November, and a delayed and shortened monsoon season caused a second drought in Indonesia. Usually undisturbed rain forests are highly resistant to fire because of their moisture, but will burn in extreme droughts. Drought and millions of dead biomass on the forest floor from selective logging made entire forests extremely prone to fire. As a result, instead of the normal flames being doused by the monsoon rains, the flames were left to ignite whole forests into an inferno. In addition, regulated fires set by timber and agribusiness firms were left to burn to clear more land for profit. Taking advantage of the extra months of the dry season, peasants who burned small amounts of land each year for subsistence farming increased their plot to grow more food. When the delayed monsoon rains arrived in Indonesia in November 1997, an estimated 2 million hectares of lush rain forest, brush and grasslands were already decimated in Kalimantan and Sumatra alone, and when the inter-monsoon season began in January, fires were spotted again all across Sumatra and Kalimantan. The same deadly cycle of the 1997 fires arose again, with thick haze from the fires spreading throughout Indonesia, until this second round of conflagrations ended in late April when rains arrived, but Indonesian officials stated that the fires had been expunged because "there was nothing left to burn."4 In fact, El Nino and La Nina were predicted well before they had any effect on Indonesia, but many parties ignored the warning and continued their usual burning of the forest. (source ...>>)

more.. »