Reference
- Ancient Antarctic ice melt caused extreme sea level rise 129,000 years ago – and it could happen againRising global temperatures and warming ocean waters are causing one of the world’s coldest places to melt. While we know that human activity is causing climate change and driving rapid changes in Antarctica, the potential impacts that a warmer world would have on this region remain uncertain. Our new research might be able to provide some insight into what effect a warmer world would have in Antarctica, by looking at what happened more than 129,000 years ago.
We found that the mass melting of the West Antarctic Ice Sheet was a major cause of high sea levels during a period known as the Last Interglacial (129,000-116,000 years ago). The extreme ice loss caused more than three metres of average global sea level rise – and worryingly, it took less than 2˚C of ocean warming for it to occur.
To conduct our research, we travelled to an area on the West Antarctic Ice Sheet and drilled into so-called blue ice areas to reconstruct the glacial history of this ice sheet.
Blue ice areas are areas of ancient ice which have been brought to the surface by fierce, high-density winds, called katabatic winds. When these winds blow over mountains, they remove the top layer of snow and erode the exposed ice. As the ice is removed by the wind, ancient ice is brought to the surface, which offers insight into the ice sheet’s history.
While most Antarctic researchers drill deep into the ice to extract their samples, we were able to use a technique called horizontal ice core analysis. As you travel closer to the mountains of the ice sheet, the ice that been brought to the surface by these winds progressively gets older. We then were able to take surface samples on a straight, horizontal line across the blue ice area to reconstruct what happened to the ice sheet in the past.
Our team took many measurements. We first looked at the fine layers of volcanic ash in the ice to pinpoint when the mass melting took place. Alarmingly, the results showed that most ice loss happened at the start of Last Interglacial warming, some 129,000 years ago – showing how sensitive the Antarctic is to higher temperatures. We think it’s likely this melting started well before the ocean warmed by 2˚C. This is concerning to us today, as ocean temperatures continue to increase, and the West Antarctic is already melting.
We also measured temperature-sensitive water molecules across the blue ice area. These isotopes revealed a large shift in temperatures, highlighting a major gap in our record at the start of the Last Interglacial. This indicates a period of sustained ice loss over thousands of years.
This period of missing ice coincides with extreme sea level rise, suggesting rapid ice melt from the West Antarctic Ice Sheet. DNA testing of ancient microbes preserved in the ice revealed an abundance of methane-consuming bacteria. Their presence suggests that the release of methane gases from sediments under the ice sheet may have also played a role in accelerating the warming process.
The West Antarctic ice sheet can tell us a lot about the effect of warming ocean temperatures because it rests on the seabed. It’s surrounded by large areas of floating ice, called ice shelves, that protect the central part of the sheet. As warmer ocean water travels into cavities beneath the ice shelves, ice melts from below, thinning the shelves and making the central sheet highly vulnerable to warming ocean temperatures. This process is currently being researched on the West Antarctic Thwaites Glacier, nicknamed the “Doomsday Glacier”.
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Perspectives
Coral Whisperers
In recent years, a catastrophic global bleaching event devastated many of the world's precious coral reefs. Working on the front lines of ruin, today's coral scientists are struggling to save these important coral reef ecosystems from the imminent threats of rapidly warming, acidifying, and polluted oceans. Coral Whisperers captures a critical moment in the history of coral reef science. Gleaning insights from over one hundred interviews with leading scientists and conservation managers, Irus Braverman documents a community caught in an existential crisis and alternating between despair and hope. In this important new book, corals emerge not only as signs and measures of environmental catastrophe, but also as catalysts for action.
Monitoring and Prediction of Tropical Cyclones in the Indian Ocean and Climate Change
This book deals with recent advances in our understanding and prediction of tropical cyclogenesis, intensification and movement as well as landfall processes like heavy rainfall, gale wind and storm surge based on the latest observational and numerical weather prediction (NWP) modeling platforms. It also includes tropical cyclone (TC) management issues like early warning systems, recent high impact TC events, disaster preparedness, assessment of risk and vulnerability including construction, archiving and retrieval of the best tracking and historical data sets, policy decision etc., in view of recent findings on climate change aspects and their impact on TC activity. The chapters are authored by leading experts, both from research and operational environments. This book is relevant to cyclone forecasters and researchers, managers, policy makers, graduate and undergraduate students. It intends to stimulate thinking and hence further research in the field of TCs and climate change, especially over the Indian Ocean region and provides high-quality reference materials for all the users mentioned above for the management of TCs over this region.
Sustaining Ocean Observations to Understand Future Changes in Earth's Climate
The ocean is an integral component of the Earth (TM)s climate system. It covers about 70% of the Earth (TM)s surface and acts as its primary reservoir of heat and carbon, absorbing over 90% of the surplus heat and about 30% of the carbon dioxide associated with human activities, and receiving close to 100% of fresh water lost from land ice. With the accumulation of greenhouse gases in the atmosphere, notably carbon dioxide from fossil fuel combustion, the Earth (TM)s climate is now changing more rapidly than at any time since the advent of human societies. Society will increasingly face complex decisions about how to mitigate the adverse impacts of climate change such as droughts, sea-level rise, ocean acidification, species loss, changes to growing seasons, and stronger and possibly more frequent storms. Observations play a foundational role in documenting the state and variability of components of the climate system and facilitating climate prediction and scenario development. Regular and consistent collection of ocean observations over decades to centuries would monitor the Earth (TM)s main reservoirs of heat, carbon dioxide, and water and provides a critical record of long-term change and variability over multiple time scales. Sustained high-quality observations are also needed to test and improve climate models, which provide insights into the future climate system. Sustaining Ocean Observations to Understand Future Changes in Earth (TM)s Climate considers processes for identifying priority ocean observations that will improve understanding of the Earth (TM)s climate processes, and the challenges associated with sustaining these observations over long timeframes.
The Impact of Melting Ice on the Ecosystems in Greenland Sea
Arctic marine ecosystems are largely impacted by changes associated with global warming. The sea ice in Greenland Sea plays an important role in regional and global climate system. The book investigate the relationships between phytoplankton biomass, measured using remotely sensed chlorophyll-a (CHL), aerosol optical depth (AOD) and sea-ice cover (ICE) in the Greenland Sea (20°W-10°E, 65-85°N) over the period 2003-2012. First hand Satellite data was used to do correlation analysis. Enhanced statistics methods, such as lag regression method and cointegration analysis method are used for correlation and regression analysis between 2 variables (up to 3 variables). ARMA model was used to prediction time series in the future 3 years. The book not only gives outline of ecosystem in Greenland Sea, how the ice impact to the local ecosystems, but also provides valuable statistical methods on analysis correlations and predicting the future ecosystems.
Coral Bleaching
One of the most dire consequences of global climate change for coral reefs is the increased frequency and severity of mass coral bleaching events. This volume provides information on the causes and consequences of coral bleaching for coral reef ecosystems, from the level of individual colonies to ecosystems and at different spatial scales, as well as a detailed analysis of how it can be detected and quantified. Future scenarios based on modelling efforts and the potential mechanisms of acclimatisation and adaptation are reviewed. The much more severe coral bleaching events experienced on Caribbean coral reefs (compared with those of the Indo-Pacific) are discussed, as are the differences in bleaching susceptibility and recovery that have been observed on smaller geographic scales.
Antarctic Sea Ice Variability in the Southern Ocean-Climate System
The sea ice surrounding Antarctica has increased in extent and concentration from the late 1970s, when satellite-based measurements began, until 2015. Although this increasing trend is modest, it is surprising given the overall warming of the global climate and the region. Indeed, climate models, which incorporate our best understanding of the processes affecting the region, generally simulate a decrease in sea ice. Moreover, sea ice in the Arctic has exhibited pronounced declines over the same period, consistent with global climate model simulations. For these reasons, the behavior of Antarctic sea ice has presented a conundrum for global climate change science. The National Academies of Sciences, Engineering, and Medicine held a workshop in January 2016, to bring together scientists with different sets of expertise and perspectives to further explore potential mechanisms driving the evolution of recent Antarctic sea ice variability and to discuss ways to advance understanding of Antarctic sea ice and its relationship to the broader ocean-climate system. This publication summarizes the presentations and discussions from the workshop.
Coral Bleaching
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High ocean temperatures caused mass bleaching in parts of the Great Barrier Reef. In early 2016, scientists mapped the destruction and found the worst hit were along Cape York Peninsula; if the coral does not replace the expelled algae, it will slowly starve to death and infection can occur. Dr. Tracy Ainsworth compares normal healthy tissue to the bleached versions.
Warming the Arctic
- Films on Demand This link opens in a new windowComputer models show the flooding and destruction that would occur if sea levels rise 6 to 8 meters. It would take only 3-5 degrees C to melt most of the Greenland ice sheet. In the last 50 years, the Arctic has warmed by 2 degrees. Humans need to act now to reduce greenhouse gasses caused by burning fossil fuels.
Melting Ice, Rising Seas
- Films on Demand This link opens in a new windowThe rising temperatures of global climate change are melting the world’s ice. Most notable are the shrinking ice sheets of Greenland and western Antarctica, which have shown dramatic loss in recent years. Travel with this science bulletin to the glaciers of Greenland and to fossilized coral reefs of the Florida Keys, where earth scientists are studying geologic records of past warming to predict future ice loss and associated sea level rise. From the American Museum of Natural History.
Online Resources
- Coral bleaching Thermal adaptation in reef coral symbiontsMany corals bleach as a result of increased seawater temperature, which causes them to lose their vital symbiotic algae (Symbiodinium spp.) - unless these symbioses are able to adapt to global warming, bleaching threatens coral reefs worldwide. Here I show that some corals have adapted to higher temperatures, at least in part, by hosting specifically adapted Symbiodinium. If other coral species can host these or similar Symbiodinium taxa, they might adapt to warmer habitats relatively easily.
- Lag Effects in the Impacts of Mass Coral Bleaching on Coral Reef Fish, Fisheries, and EcosystemsRecent episodes of coral bleaching have led to wide-scale loss of reef corals and raised concerns over the effectiveness of existing conservation and management efforts. The 1998 bleaching event was most severe in the western Indian Ocean, where coral declined by up to 90% in some locations. Using fisheries-independent data, we assessed the long-term impacts of this event on fishery target species in the Seychelles, the overall size structure of the fish assemblage, and the effectiveness of two marine protected areas (MPAs) in protecting fish communities. The biomass offished species above the size retained in fish traps changed little between 1994 and 2005, indicating no current effect on fishery yields. Biomass remained higher in MPAs, indicating they were effective in protecting fish stocks. Nevertheless, the size structure of the fish communities, as described with size-spectra analysis, changed in both fished areas and MPAs, with a decline in smaller fish (<30 cm) and an increase in larger fish (>45 cm). We believe this represents a time-lag response to a reduction in reef structural complexity brought about because fishes are being lost through natural mortality and fishing, and are not being replaced by juveniles. This effect is expected to be greater in terms offisheries productivity and, because congruent patterns are observed for herbivores, suggests that MPAs do not offer coral reefs long-term resilience to bleaching events. Corallivores and planktivores declined strikingly in abundance, particularly in MPAs, and this decline was associated with a similar pattern of decline in their preferred corals. We suggest that climate-mediated disturbances, such as coral bleaching, be at the fore of conservation planning for coral reefs.
Rehabilitating Coral
- Films on Demand This link opens in a new windowScott Heron and Bill Leggat experiment with the abilities of coral to recover from bleaching. Temperature tanks will mimic what happened in the northern portion of the Great Barrier Reef. Climate change experts predict that temperatures will rise for the next 30 to 40 years; coral will not be able to adapt.