Constantine Alexander's blog

Warming ocean could start big shift of Antarctic ice

Chris Fogwill in Antarctica

Fast-flowing and narrow glaciers have the potential to trigger massive changes in the Antarctic ice sheet and contribute to rapid ice-sheet decay and sea-level rise, a new study has found.

Research results published in the journal Proceedings of the National Academy of Sciences reveal in more detail than ever before how warming waters in the Southern Ocean are connected intimately with the movement of massive ice-sheets deep in the Antarctic interior.

"It has long been known that narrow glaciers on the edge of the Antarctica act as discrete arteries termed ice streams, draining the interior of the ice sheet," says Dr Chris Fogwill, an author of the study and an ARC Future Fellow with the UNSW Climate Change Research Centre.

"However, our results have confirmed recent observations suggesting that ocean warming can trigger increased flow of ice through these narrow corridors. This can cause inland sectors of the ice-sheet - some larger than the state of Victoria - to become thinner and flow faster."

The researchers, led by Dr Nicholas Golledge from Victoria University of Wellington, New Zealand, tested high-resolution model simulations against reconstructions of the Antarctic ice sheet from 20,000 years ago, during the last glacial maximum.

They used a new model, capable of resolving responses to ice-streams and other fine- scale dynamic features that interact over the entire ice sheet. This had not previously been possible with existing models. They then used this data to analyse the effects of a warming ocean over time.

The results showed that while glacier acceleration triggered by ocean warming is relatively localized, the extent of the resultant ice-sheet thinning is far more widespread. This observation is particularly important in light of recently observed dynamic changes at the margins of Antarctica. It also highlighted areas that are more susceptible than others to changes in ocean temperatures.

The glaciers that responded most rapidly to warming oceans were found in the Weddell Sea, the Admundsen Sea, the central Ross Sea and in the Amery Trough.

The finding is important because of the enormous scale and potential impact the Antarctic ice sheets could have on sea-level rise if they shift rapidly, says Fogwill. "To get a sense of the scale, the Antarctic ice sheet is 3km deep - three times the height of the Blue Mountains in many areas - and it extends across an area that is equivalent to the distance between Perth and Sydney.

"Despite its potential impact, Antarctica's effect on future sea level was not fully included in the last IPCC report because there was insufficient information about the behaviour of the ice sheet. This research changes that. This new, high-resolution modelling approach will be critical to improving future predictions of Antarctica's contribution to sea level over the coming century and beyond."

Contact: Bob Beale
bbeale@unsw.edu.au
61-411-705-435
University of New South Wales

 

 

Major changes needed to protect Australia's species and ecosystems

A study has highlighted the sensitivity of Australia's species and ecosystems to climate change, and the need for new ways of thinking about biodiversity conservation.

'Climate change is likely to start to transform some of Australia's natural landscapes by 2030,' lead researcher, CSIRO's Dr Michael Dunlop said. 'By 2070, the ecological impacts are likely to be very significant and widespread. Many of the environments our plants and animals currently exist in will disappear from the continent. Our grandchildren are likely to experience landscapes that are very different to the ones we have known,' he said.

Dr Dunlop said climate change will magnify existing threats to biodiversity, such as habitat clearing, water extraction and invasive species. Future climate-driven changes in other sectors, such as agriculture, water supply and electricity supply, could add yet more pressure on species and ecosystems.

'These other threats have reduced the ability of native species and ecosystems to cope with the impacts of climate change,' Dr Dunlop said.

One of the challenges for policy and management will be accommodating changing ecosystems and shifting species.

The study suggests the Australian community and scientists need to start a rethink of what it means to conserve biodiversity, as managing threatened species and stopping ecological change becomes increasingly difficult.

'We need to give biodiversity the greatest opportunity to adapt naturally in a changing and variable environment rather than trying to prevent ecological change,' Dr Dunlop said.

The study highlights the need to start focussing more on maintaining the health of ecosystems as they change in response to climate change, from one type of ecosystem to another.

'This could need new expectations from the community, possibly new directions in conservation policy, and new science to guide management,' Dr Dunlop said.

'To be effective we also need flexible strategies that can be implemented well ahead of the large-scale ecological change. It will probably be too late to respond once the ecological change is clearly apparent and widespread'.

The study found the National Reserve System will continue to be an effective conservation tool under climate change, but conserving habitat on private land will be increasingly important to help species and ecosystems adapt.

The team of researchers from CSIRO carried out modelling across the whole of Australia, as well as detailed ecological analysis of four priority biomes, together covering around 80 per cent of Australia.

The study was funded by the Australian Government Department of Sustainability, Environment, Water, Population and Communities, the Department of Climate Change and Energy Efficiency and the CSIRO Climate Adaptation Flagship.

Contact: Josie Banens
Josie.Banens@csiro.au
61-262-464-422
CSIRO Australia

 

 

Surprising demographic shifts in endangered monkey population challenge conservation expectations

A new study reports increasing use of the ground among a population of the otherwise arboreal northern muriqui monkeys in Brazil. Researchers led by University of Wisconsin–Madison anthropologist Karen Strier believe the behavioral innovation may underlie demographic changes in the population over the past 30 years, including unexpected increases in both fertility and mortality. Credit: Karen Strier, University of Wisconsin–Madison

At first glance, the northern muriqui monkey is a prime conservation success story.

These Brazilian primates are critically endangered, but in the past 30 years a population on a private reserve has grown from just 60 individuals to some 300, now comprising almost a third of the total remaining animals.

As the population grows, though, it is offering researchers a glimpse into a new phase of recovery as it begins to face the limitations of its habitat. A recent analysis of the factors contributing to this population's tremendous growth reveals surprising trends that raise new questions about conservation, recovery and what constitutes a healthy population.

University of Wisconsin–Madison anthropologist Karen Strier has led observational field studies of this muriqui population for 30 years, meticulously charting demographics and life history of hundreds of individual monkeys. An analysis, published Sept. 17 in the journal PLOS ONE with UW–Madison mathematical ecologist Anthony Ives, provides the most comprehensive, quantitative look to date at long-term demographic trends and the role of individual features such as fertility, mortality, and sex ratios.

The researchers used statistical models designed to handle multiple levels of data so they could construct a comprehensive view of the population while still accounting for variation among individual animals. The approach allowed them to identify specific demographic trends and their effects on the overall population size.

Karen Strier, Professor of Anthropologyat the University of Wisconsin–Madison

"By separating out these components we were able to see the patterns in the data," Strier says, many of which were unexpected. For example, the analyses revealed increases in both fertility and mortality – a surprising combination, especially in a population that is still growing. In addition, they documented a remarkable and unexplained shift in infant birth sex ratios from about one-third male to two-thirds male in just 28 years.

"It is an analysis that leads to more questions than answers," Ives says. A birth rate that continues to grow as the population expands flies in the face of most ecological thinking, he says, since demand for resources by larger populations usually reduces fertility. But without the observed fertility increases, the muriqui population would likely have plateaued around 200 individuals; instead, it has reached 300 and is still growing.

Strier believes the trends may be driven by behavioral changes. Though muriquis are typically arboreal animals, her field team has observed increased use of the ground – first for drinking and eating, then gradually for traveling, playing, and even mating. These data are still qualitative, but she suspects this behavioral innovation could help explain the rises in both fertility and mortality. The ground expands the monkeys' pool of available habitat and food resources but exposes them to additional dangers as well.

"On the ground, there are risks. We suspect there may be more pathogenic risks, and we know there are more predators," she says. Supporting a connection, mortality increased primarily in prime-aged males, who spend more time on the ground than females. "I've always thought it was increasing population size that was driving this increasing use of the ground, but never thought about what the potential consequences of the use of the ground might be for the population's rate of growth," she adds.

The apparent interactions between demography and behavior emphasize the need for ongoing population monitoring, Strier says. Her long-term study, in collaboration with Brazilian colleagues including biologist Sergio Mendes of the Universidade Federal do Espirito Santo, is showing that assumptions about population dynamics based on past observations may not hold true in the future.

Ives views the results as a cautionary tale for other threatened and endangered species, the vast majority of which are not monitored anywhere near as closely as Strier's muriquis.

"From the conservation standpoint I think a main message is, don't presume that the demographics will respond in a 'normal' way," he says. "Even if an area is protected you need to have a close gauge on what's going on. Protecting an area is not necessarily protecting a species."

Strier agrees that the analysis raises important questions about environmental carrying capacity – basically, how large of a population a habitat can support. "How long will it be able to grow, and if it does continue to grow, is it in danger of crashing?" she asks.

These are critical questions when considering management decisions, she adds, especially given that her study population represents a third of the entire muriqui species. On paper, population growth alone can look like success, but their demographic analysis reveals early indications of stress even as the population continues to expand.

At the same time, Strier says, their studies suggest a solution. "We know exactly what we need to do to alleviate it – expand the area, and there is area to expand the forest into. In a world with so many unsolvable problems, this seems like a solvable one."

Contact: Karen Strier
kbstrier@wisc.edu
608-262-0302
University of Wisconsin-Madison

 

 

Sea surface temperatures reach record highs on Northeast continental shelf

Changing cod distribution observed as ecosystem warms bottom to top

Atlantic Cod.

During the first six months of 2012, sea surface temperatures in the Northeast Shelf Large Marine Ecosystem were the highest ever recorded, according to the latest Ecosystem Advisory issued by NOAA's Northeast Fisheries Science Center (NEFSC). Above-average temperatures were found in all parts of the ecosystem, from the ocean bottom to the sea surface and across the region, and the above average temperatures extended beyond the shelf break front to the Gulf Stream.

The annual 2012 spring plankton bloom was intense, started earlier and lasted longer than average. This has implications for marine life from the smallest creatures to the largest marine mammals like whales. Atlantic cod continued to shift northeastward from its historic distribution center.

The Northeast US Continental Shelf Large Marine Ecosystem (LME) extends from the Gulf of Maine to Cape Hatteras, North Carolina. The NEFSC has monitored this ecosystem with comprehensive sampling programs from 1977 onward; prior to 1977, this ecosystem was also monitored by the NEFSC through a series of separate but coordinated programs dating back decades.

"A pronounced warming event occurred on the Northeast Shelf this spring, and this will have a profound impact throughout the ecosystem," said Kevin Friedland, a scientist in the NEFSC's Ecosystem Assessment Program. "Changes in ocean temperatures and the timing of the spring plankton bloom could affect the biological clocks of many marine species, which spawn at specific times of the year based on environmental cues like water temperature."

Friedland said the average sea surface temperature (SST) exceeded 10.5 degrees C (51°F) during the first half of 2012, exceeding the previous record high in 1951. Average SST has typically been lower than 9 degrees C (48°F) over the past three decades. Sea surface temperature in the region is based on both contemporary satellite remote-sensing data and long-term ship-board measurements, with historical SST conditions based on ship-board measurements dating back to 1854.

In some nearshore locations like Delaware and Chesapeake Bays in the Middle Atlantic Bight region, temperatures were more than 6 degrees C (11°F) above historical average at the surface and more than 5 degrees C (9°F) above average at the bottom. In deeper offshore waters to the north, bottom waters were 1 degree C (2°F) warmer in the eastern Gulf of Maine and greater than 2 degrees C (3.6°F) warmer in the western Gulf of Maine.

Ocean bottom temperature data cited in the advisory posted today came from a variety of sources, including eMOLT, a cooperative research program between the Northeast Fisheries Science Center and lobstermen who deploy temperature probes attached to lobster traps. While some of the temperature probes from the eMOLT program are still in the water and have not yet been returned, those that have been returned indicate that bottom water temperatures in 2012 were the warmest since the eMOLT program began in 2001.

Atlantic cod distribution in the Gulf of Maine continues a northeasterly shift, with the spring 2012 data consistent with a response to ecosystem warming. Warming ocean temperatures and the resulting impact on the distribution of 36 fish stocks was reported by the Center in a 2009 study published in Marine Ecology Progress Series. That study analyzed annual NEFSC spring survey data from 1968 to 2007 and other information and found that about half of the 36 fish stocks studied in the Northwest Atlantic Ocean, many of them commercially valuable species, have been shifting northward over the past four decades, with some disappearing from US waters as they move farther offshore.

Friedland notes that although cod didn't shift as much as other species like hake in the 2009 study, the effects of warming water on ocean currents and other ocean circulation patterns could change that. "Cod distribution continues to be dynamic, with northerly shifts detected in the spring 2012 data, consistent with a response to ecosystem warming," Friedland said. "The big question is whether or not these changes will continue, or are they a short-term anomaly?"

Mike Fogarty, who heads the Ecosystem Assessment Program, says the abundance of cod and other finfish is controlled by a complex set of factors, and that increasing temperatures in the ecosystem make it essential to monitor the distribution of many species, some of them migratory and others not.

"A complex combination of factors influence ocean conditions, and it isn't always easy to understand the big picture when you are looking at one specific part of it at one specific point in time, "Fogarty said, a comparison similar to not seeing the forest when looking at a single tree in it. "We now have information from a variety of sources collected over a long period of time on the ecosystem, and are continually adding more data to clarify specific details. The data clearly show a relationship between all of these factors."

The 2012 spring plankton bloom, one of the longest duration and most intense in recent history, started at the earliest date recorded since the ocean color remote sensing data series began in 1998. In some locations, the spring bloom began in February, and was fully developed by March in all areas except Georges Bank, which had an average although variable spring bloom. The 2012 spring bloom in the Gulf of Maine began in early March, the earliest recorded bloom in that area.

"What this early start means for the Northeast Shelf ecosystem and its marine life is unknown," Fogarty said. "What is known is that things are changing, and we need to continue monitoring and adapting to these changes."

Intensive surveys of environmental conditions on the Northeast Shelf from Cape Hatteras, North Carolina to Nova Scotia were conducted from 1977 to 1987 as part of the Marine Resources Monitoring, Assessment & Prediction (MARMAP) program. The efforts continued at reduced levels through the 1990s and are ongoing today as part of the Center's Ecosystems Monitoring (EcoMon) program.

Plankton samples are collected six times a year in each of the four subareas of the Northeast Shelf: the Middle Atlantic Bight, Southern New England, Georges Bank, and the Gulf of Maine. EcoMon scientists also collect water samples and other oceanographic data about conditions during each season in each of the four areas to provide a long-term view of changing conditions on the Shelf.

Ecosystem advisories have been issued twice a year by the NEFSC's Ecosystems Assessment Program since 2006 as a way to routinely summarize overall conditions in the region. The reports show the effects of changing coastal and ocean temperatures on fisheries from Cape Hatteras to the Canadian border. The advisories provide a snapshot of the ecosystem for the fishery management councils and also a broad range of stakeholders from fishermen to researchers.

The Spring 2012 Ecosystem Advisory with supporting information is available online.

Contact: Shelley Dawicki
Shelley.Dawicki@noaa.gov
508-495-2378
NOAA Fisheries Northeast Fisheries Science Center