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- Choices made now are critical for the future of our ocean and cryosphere — IPCC
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Greenland saw a doubling of mass loss over the same period.
The report expects this to continue throughout the 21st Century and beyond. This will have huge consequences for millions of people. All this extra water gushing down to the seas is driving up average ocean water levels around the world. That will continue over the decades to come.
- SOTC: Overview | National Snow and Ice Data Center.
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This new report says that global average sea levels could increase by up to 1. This is a rise of 10cm on previous IPCC projections because of the larger ice loss now happening in Antarctica. On the east coast of England, most of the city of Hull lies below the level of a typical high tide. The sea here can be both a source of wealth and a threat to life. So the conclusions of the IPCC report have real meaning. A storm surge on a winter's night six years ago found a weak link in a sea wall and flooded businesses and homes.
New defences were ordered and the construction teams are now at work along the shore. But the barriers cannot protect everyone. Computer simulations, developed by the University of Hull, show that if the level of the ocean is one metre higher than now the centre of the city ought to be fine but neighbouring areas will go under.
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This highlights a painful question, faced in low-lying places the world over: which should be saved and which should be abandoned as the waters rise? The scientists also say that relocating people away from threatened communities is worth considering "if safe alternative localities are available". One of the key messages is the way that the warming of the oceans and cryosphere the icy bits on land is part of a chain of poor outcomes that will affect millions of people well into the future. Under higher emissions scenarios, even wealthy megacities such as New York or Shanghai and large tropical agricultural deltas such as the Mekong will face high or very high risks from sea level rise.
The report says that a world with severely increased levels of warm water will in turn give rise to big increases in nasty and dangerous weather events, such as surges from tropical cyclones. The ways in which you may be affected are vast - flood damage could increase by two or three orders of magnitude. The acidification of the oceans thanks to increased levels of CO2 is threatening corals, to such an extent that even at 1. When CO2 is dissolved in water it forms carbonic acid. So, the more carbon dioxide that dissolves in our oceans, the more acidic the water gets.
Species of fish will move as ocean temperatures rise. Seafood safety could even be compromised because humans could be exposed to increased levels of mercury and persistent organic pollutants in marine plants and animals. These pollutants are released from the same fossil fuel burning that release the climate warming gas CO2. Even our ability to generate electricity will be impaired as warming melts the glaciers, altering the availability of water for hydropower. Huge amounts of carbon are stored in the permanently frozen regions of the world such as in Siberia and Northern Canada.
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The big worry is that this could free up "tens to hundreds of billions of tonnes" of CO2 and methane to the atmosphere by This would be a significant limitation on our ability to limit global warming in the centuries to come. However, there are some warnings in the report that some changes may not be easily undone. In contrast to these observations and to those elsewhere in the alpine Southern Hemisphere, glaciers in the McMurdo Dry Valleys of Antarctica appear to be in equilibrium, since their positions have not changed since their observation began in Fountain et al.
The removal of water from long-term storage in glacial ice increases summer streamflow and global sea level. However, as the mass of glaciers decline, their ability to support summer streamflow declines, and they decrease in their ability to buffer the watersheds against drought. Sea ice figure 2b occurs in the Arctic; in the Southern Ocean surrounding Antarctica and the Baltic Sea; and in part of the northwest Pacific, from the Siberian coast down to the Japanese island of Hokkaido.
Choices made now are critical for the future of our ocean and cryosphere — IPCC
Most sea ice forms and melts annually, with perennial multiyear ice restricted to the high latitudes of the Arctic and Antarctica. Changes in sea ice alter the extent and distribution of foraging platforms for larger mammals and refuge habitat for smaller species. At the Palmer Peninsula, seasonal sea-ice cover has been shrinking at astonishing rates because of increases in onshore winds driven by hemispheric changes in atmospheric circulation.
The duration of sea-ice cover has declined by 85 days since Stammerjohn et al.
go to link Seasonal lake and river ice occur in all temperate regions, with durations of days to months, whereas perennial ice cover is only found at extremely high latitudes and elevations. The date of lake-ice formation and breakup is commonly recorded for commercial purposes related to shipping, trapping, fishing, ice harvesting, and transportation and yields an extensive long-term record Magnuson et al.
Since , lake-ice duration in the Northern Hemisphere has decreased by 12 days per century, which is equivalent to a warming of 1. A year record of ice thickness in late March on an alpine lake in the Niwot Ridge LTER site shows a consistent thinning of the ice cover at 2. Ice cover exhibits strong control over exchanges in gases and material, solar radiation, and heat between aquatic habitats and the atmosphere. The duration of ice exerts a profound influence on the patterns of water circulation and thermal stratification, which are closely linked to the life cycles of aquatic organisms and to the biogeochemical cycling of the ecosystem.
Snow figure 2a is the largest component of the cryosphere in areal extent. Increased snowfall and snow depth have been reported at the highest-elevation sites of the western United States Williams et al. In the Pacific Northwest, extensive snow-covered regions are now deemed at risk in terms of their capacity to provide reliable water yields because of atmospheric warming, altitudinal shifts in the distribution of snow and rain, and declining winter snowpacks Nolin and Daly Winter snow depths have also been decreasing throughout the northeastern United States.
For example, at the Hubbard Brook LTER site in New Hampshire, the maximum snow depth has declined by 25 cm 7 cm water equivalent , and snow cover duration has decreased by 21 days over the past 53 years Campbell et al. One simple metric in the attempt to capture potential ecosystem vulnerability to changes in the cryosphere across ecosystems is the duration of frost and freezing temperatures table 2 , figure 3.
Vulnerability can be thought of as susceptible to increased or decreased frost or freezing periods. For example, ecosystems that do not experience frost, such as those in the tropics, are highly vulnerable to cold temperatures. Significant ecosystem changes could be expected if the climate were to cool, making frost commonplace. Alternatively, ecosystems accustomed to long frozen periods, such as polar and high alpine ecosystems, are highly vulnerable to warm temperatures.
Those ecosystems exposed to moderate periods of frost or freezing would be expected to be less vulnerable to changes in temperature.
We focus on the warming climate, and as such, the tropical ecosystems will not be directly exposed to cryospheric losses, whereas polar and high alpine ecosystems may be the most vulnerable to such change. In table 2 and figure 3 , we can see the vulnerability of the major ecosystem research sites under study by US scientists. Record refers to the length of the air-temperature record used to estimate frost and freezing duration at each location. Duration of frost and freezing periods at LTER and related long-term research sites, from climate records.
See table 2 for the site abbreviations. The various components of the cryosphere provide physical habitat for diverse organisms. Iconic examples include polar bears and penguins in sea ice and pikas in rock glaciers rock debris with ice filling the void spaces between the rocks; the mass flows downhill , but many other species ranging in size from microbes to whales inhabit permafrost, glaciers, sea-ice, and snow-covered landscapes.
As these habitats shrink and disappear, resident species are forced to migrate, often tracking the distribution of receding frozen habitats across the landscape. Since different organisms respond and move at different rates e. Although these processes are occurring at unprecedented rates in response to rapid climate warming, it has required decades of coordinated observations to document significant change and to uncover the mechanisms linking climate forcing to ecosystem responses. Prolonged, systematic studies of this type are a key contribution of LTER.
The LTER Network of sites facilitates long-term observations, experiments, and comparative studies that enable us to identify common processes and mechanisms across diverse ecosystems. The highly interdisciplinary nature of LTER helps to quickly reveal interpretations of causes and consequences and needed adjustments of monitoring approaches to catch signals of previously unmonitored or unanticipated system behaviors.
Here, we present some notable examples of ecological and biogeochemical changes in response to cryosphere loss. Decadal-scale declines or distributional shifts in snow- and ice-dependent species are now extensive and well documented Chapin et al. When ice-dependent species suffer habitat loss, the changes in frozen habitats glaciers, sea ice, snowpacks, and permafrost impose both bottom-up and top-down forcings on terrestrial and aquatic ecosystems. Ice loss affects ecosystems directly through the loss of physical habitat and through alterations in thermal conditions and indirectly by altering light and nutrient supply to primary producers.
Both Arctic and Antarctic sea ice harbor a resident microbial community of diatoms, other phytoplankton, bacteria, and protozoan grazers that contributes to the total primary production of polar seas. Like sea ice, ice and rock glaciers are habitats for specially adapted species that may disappear as glaciers retreat and their cold, glacier-fed streams disappear. The American pika Ochotona princeps —although it is not as well known or charismatic as penguins or polar bears—is attaining new status as a poster child for glacier loss and climate change.
Pikas do not hibernate and use subsurface microclimates in rocky debris to persist where surface conditions would preclude their survival. Despite this adaptation, some local pika extinctions in the Northwest have been linked to cold exposure caused by a loss of insulating snow cover Ray et al. Permafrost thaw also results in habitat disappearance for its resident species.
Because permafrost occurs in so many different habitats in different stages of development, its loss may trigger primary or secondary successions. Widespread past and projected future reductions in snow-cover extent, duration, depth, and water equivalent can also have extensive ecological repercussions. Many plant and animal species are adapted to snow-cover conditions and will perish if they are unable to migrate or tolerate less snow cover. Even so, not all animals that live in cold environments respond negatively to reductions in snow cover.
For example, ungulates such as white-tailed deer, mule deer, elk, and caribou expend less energy and are less susceptible to predation when snowpacks are shallower. Some of the species most susceptible to snow-cover loss are those that overwinter below ground, since snow insulates the subsurface and moderates its temperature.
The shortgrass steppe in the western United States receives little snowfall and therefore presents an endpoint in the spectrum of snow cover.