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World ocean thermohaline circulation World ocean thermohaline circulation
The global conveyor belt thermohaline circulation is driven primarily by the formation and sinking of deep water (from around 1500m to the Antarctic bottom water overlying the bottom of the ocean) in the Norwegian Sea. When the strength of the haline forcing increases due to excess precipitation, runoff, or ice melt the conveyor belt will weaken or even shut down. The variability in the strength of the conveyor belt will lead to climate change in...
01 Jun 2007 - by Hugo Ahlenius, UNEP/GRID-Arendal
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Monthly average sea ice extent globally and in both hemispheres Monthly average sea ice extent globally and in both hemispheres
In the Arctic, winter sea ice extends over an area of approximately 15 million km2 at its peak in March and up to 7 million km2 in September, at the end of the summer melt season. Corresponding numbers for the Southern Ocean around the Antarctic continent are approximately 3 million km2 in February during the Antarctic summer and 18 million km2 at the height of winter in September. In regions with seasonal sea ice, the ice cover achieves a thickn...
01 Oct 2007 - by Hugo Ahlenius, UNEP/GRID-Arendal
4
Mean snow-cover extent in the Northern Hemisphere 1966-2006 Mean snow-cover extent in the Northern Hemisphere 1966-2006
Snow occurs predominantly on the northern continents, on the sea ice of the Arctic Ocean and on Antarctica. On the Northern Hemisphere continents, snow covers a maximum mean area of 45.2 million km2, typically in January. The minimum snow-cover extent usually occurs in August and covers a mean area of 1.9 million km2, most of which is snow on the Greenland ice sheet and on mountain glaciers. As a result, snow cover is the surface characteristic r...
01 Oct 2007 - by Hugo Ahlenius, UNEP/GRID-Arendal
3
Permafrost extent in the Northern Hemisphere Permafrost extent in the Northern Hemisphere
Permafrost zones occupy up to 24 per cent of the exposed land area of the Northern Hemisphere. Permafrost is also common within the vast continental shelves of the Arctic Ocean. This subsea permafrost formed during the last glacial period when global sea levels were more than 100 m lower than at present and the shelves were exposed to very harsh climate conditions. Subsea permafrost is slowly thawing at many locations. Permafrost of various tempe...
01 Jun 2007 - by Hugo Ahlenius, UNEP/GRID-Arendal
5
Greenland, showing rates of surface-elevation change between the late 1990s and 2003 Greenland, showing rates of surface-elevation change between the late 1990s and 2003
Mass-balance estimates for Greenland show thickening at high elevations since the early 1990s at rates that increased to about 4 cm per year after 2000, consistent with expectations of increasing snowfall in a warming climate. However, this mass gain is far exceeded by losses associated with large increases in thinning of the ice sheet near the coast. Total loss from the ice sheet more than doubled, from a few tens of billions of tonnes per year ...
01 Jun 2007 - by Hugo Ahlenius, UNEP/GRID-Arendal
4
The Cryosphere, world map The Cryosphere, world map
Snow and the various forms of ice - the cryosphere - play different roles within the climate system. The two continental ice sheets of Antarctica and Greenland actively influence the global climate over time scales of millennia to millions of years, but may also have more rapid effects on, for example, sea level. Snow and sea ice, with their large areas but relatively small volumes, are connected to key interactions and feedbacks at global scales...
01 Jun 2007 - by Hugo Ahlenius, UNEP/GRID-Arendal
4
Sea ice concentration change over the 21st century as projected by climate models Sea ice concentration change over the 21st century as projected by climate models
The data are taken from climate model experiments of 12 (out of 24) different models that were conducted for the IPCC Assessment Report 4 using the SRES A1B greenhouse gas emission scenario. Plots on the right show changes in late summer and those on the left show changes in late winter. Notes: 1) sea ice extent is the area in which a defined minimum of sea ice can be found. sea ice concentration is the proportion of the ocean area actually cover...
01 Jun 2007 - by Hugo Ahlenius, UNEP/GRID-Arendal
3
Monthly average sea ice extent globally and in both hemispheres (radial) Monthly average sea ice extent globally and in both hemispheres (radial)
In the Arctic, winter sea ice extends over an area of approximately 15 million km2 at its peak in March and up to 7 million km2 in September, at the end of the summer melt season. Corresponding numbers for the Southern Ocean around the Antarctic continent are approximately 3 million km2 in February during the Antarctic summer and 18 million km2 at the height of winter in September. In regions with seasonal sea ice, the ice cover achieves a thickn...
01 Oct 2007 - by Hugo Ahlenius, UNEP/GRID-Arendal
4
Regional changes in Arctic and Antarctic sea ice Regional changes in Arctic and Antarctic sea ice
There are major regional differences for the Arctic sea ice, with the strongest decline in ice extent observed for the Greenland Sea (10.6 per cent per decade). The smallest decreases of annual mean sea ice extent were found in the Arctic Ocean, the Canadian Archipelago and the Gulf of St. Lawrence. In the marginal Arctic seas off Siberia (the Kara, Laptev, East Siberian and Chukchi Seas) a slight negative, but not significant, trend in ice exten...
01 Jun 2007 - by Hugo Ahlenius, UNEP/GRID-Arendal
4
Trend in mean depth of catch since 1950 Trend in mean depth of catch since 1950
Fisheries catches increasingly originate from deep areas. Over the years due to depletion in fish stocks the fishing industry has resorted to fishing at greater depths and increasing the damage to fish stocks and the ocean floor.
30 Nov 2007 - by Philippe Rekacewicz, Emmanuelle Bournay, UNEP/GRID-Arendal
4
Marine, coastal, and island systems Marine, coastal, and island systems
Marine systems are the world’s oceans. For mapping purposes, the map shows ocean areas where the depth is greater than 50 meters. Global fishery catches from marine systems peaked in the late 1980s and are now declining despite increasing fishing effort.
30 Nov 2007 - by Philippe Rekacewicz, Emmanuelle Bournay, UNEP/GRID-Arendal
5
Natural resources - marine resources Natural resources - marine resources
Primary ocean productivity, as measured in grammes of carbon per square meter, from remote sensing imagery outlines the areas with rich marine life. These areas are characterised by an abundance of marine life and they provide natural resources in terms of fisheries and harvesting of these resources. The map is a part of a set, presenting different natural resources, with a focus on developing countries, and the use of natural resources for econo...
01 Feb 2008 - by Hugo Ahlenius, UNEP/GRID-Arendal
4
Fiji, topographic map Fiji, topographic map
The Republic of Fiji is a small island country in the South Pacific Ocean. The country has a population of 850 000 people spread out over an archipelago of islands. The largest ones, Viti Levu and Vanua Leva houses the majority of the inhabitants.
12 May 2008 - by Hugo Ahlenius, UNEP/GRID-Arendal
2
Greenland, showing rates of surface-elevation change between the late 1990s and 2003 Greenland, showing rates of surface-elevation change between the late 1990s and 2003
Mass-balance estimates for Greenland show thickening at high elevations since the early 1990s at rates that increased to about 4 cm per year after 2000, consistent with expectations of increasing snowfall in a warming climate. However, this mass gain is far exceeded by losses associated with large increases in thinning of the ice sheet near the coast. Total loss from the ice sheet more than doubled, from a few tens of billions of tonnes per year ...
01 Jun 2007 - by Hugo Ahlenius, UNEP/GRID-Arendal
4
Ecoregions in Antarctica Ecoregions in Antarctica
Antarctica represents a very unique and special case on our planet. With the richness of the Southern Ocean, the coasts and the Southern islands have relatively high biodiversity and biomass in the form of numerous sea birds - such as penguins and mammals such as seals and sea lions - primarily around the Antarctic peninsula - in the Marielandia Arctic Tundra ecoregion. In contrast - the inland of the Antarctic continent are a cold, windy and inh...
31 Jul 2008 - by Hugo Ahlenius, UNEP/GRID-Arendal
3
Coldwater coral reefs, distribution Coldwater coral reefs, distribution
Scientists are just beginning to learn about the many species in the remote, deep waters of the polar oceans. Corals, for example, are not limited to the warm, shallow waters of the tropics. They also exist in many cold, deep waters all over the world, including Arctic and sub-Antarctic waters. Coral reefs are marine ridges or mounds, which have formed over millennia as a result of the deposition of calcium carbonate by living organisms, predomin...
31 Jul 2008 - by Hugo Ahlenius, UNEP/GRID-Arendal
4
Vegetation and land cover in the Arctic Vegetation and land cover in the Arctic
The land mass in the Arctic - Greenland and parts of Canada, Alaska, Russia and the Nordic countries - surrounds the Arctic Ocean. In the low Arctic, down to the temperate regions, the taiga coniferous forests represents a vast band of deep forests. North of the taiga, the tundra of the Arctic - with low vegetation, shrubs and various degrees of permafrosts spreads out. Beyond the tundra, there might be barren regions with only rock and few plant...
31 Jul 2008 - by Hugo Ahlenius, UNEP/GRID-Arendal
5
Fisheries in the Southern Ocean Fisheries in the Southern Ocean
Fisheries, together with tourism, represents a major economic activity around Antarctica. In the old days whales were hunted for oil - these days fish and krill are captured for fish meal and human consumption. The areas in the Southern Atlantic are vastly more productive, and this is where most of the fish is caught. The top fishing vessels hail from Japan, Ukraine and Poland. Worth mentioning is that these figures are still small compared to th...
31 Jul 2008 - by Hugo Ahlenius, UNEP/GRID-Arendal
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Depht-corrected density of Labrador Sea water (northern North Atlantic) at 200-800 m depth Depht-corrected density of Labrador Sea water (northern North Atlantic) at 200-800 m depth
The global ocean circulation system will change under the strong influence of arctic warming.
27 Oct 2009 - by Riccardo Pravettoni, UNEP/GRID-Arendal
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Temperature anomalies of the intermediate Atlantic Water in Arctic Ocean Temperature anomalies of the intermediate Atlantic Water in Arctic Ocean
The Arctic Ocean connections are changing
27 Oct 2009 - by Laura Margueritte
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