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Environment   Aug 29, 2017 by Likhith

ARCTIC OCEAN

This indicator tracks the extent, age, and melt season of sea ice in the Arctic Ocean.

• Figure 1. March and September Monthly Average Arctic Sea Ice Extent, 1979–2016

  This figure shows Arctic sea ice extent for the months of September and March of each year from 1979 through 2016. September and March are when the minimum and maximum extent typically occur each year
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• September 2012 had the lowest sea ice extent ever recorded, 44 percent below the 1981–2010 average for that month.
• The September 2016 sea ice extent was more than 700,000 square miles less than the historical 1981–2010 average for that month (see Figure 1)—a difference more than two and a half times the size of Texas. March sea ice extent reached the lowest extent on record in 2015 and hit roughly the same low again in 2016—about 7 percent less than the 1981–2010 average.
• All months have shown a negative trend in sea ice extent over the past several decades. The largest year-to-year decreases have occurred in the summer and fall months.2,3
• Evidence of the age of Arctic sea ice suggests that fewer patches of ice are persisting for multiple years (i.e., generally thick ice that has survived one or more melt seasons) (see Figure 2). The proportion of sea ice five years or older has declined dramatically over the recorded time period, from more than 30 percent of September ice in the 1980s to 9 percent in 2015. A growing percentage of Arctic sea ice is only one or two years old. Less old multi-year ice implies that the ice cover is thinning, which makes it more vulnerable to further melting.
• Since 1979, the length of the melt season for Arctic sea ice has grown by 37 days (see Figure 3). Arctic sea ice now starts melting 11 days earlier and it starts refreezing 26 days later than it used to, on average

OCEAN ACIDIFICATION

When carbon dioxide (CO₂) is absorbed by seawater, chemical reactions occur that reduce seawater pH, carbonate ion concentration, and saturation states of biologically important calcium carbonate minerals. These chemical reactions are termed "ocean acidification" or "OA" for short. Calcium carbonate minerals are the building blocks for the skeletons and shells of many marine organisms. In areas where most life now congregates in the ocean, the seawater is supersaturated with respect to calcium carbonate minerals. This means there are abundant building blocks for calcifying organisms to build their skeletons and shells. However, continued ocean acidification is causing many parts of the ocean to become undersaturated with these minerals, which is likely to affect the ability of some organisms to produce and maintain their shells.

Since the beginning of the Industrial Revolution, the pH of surface ocean waters has fallen by 0.1 pH units. Since the pH scale, like the Richter scale, is logarithmic, this change represents approximately a 30 percent increase in acidity. Future predictions indicate that the oceans will continue to absorb carbon dioxide and become even more acidic. Estimates of future carbon dioxide levels, based on business as usual emission scenarios, indicate that by the end of this century the surface waters of the ocean could be nearly 150 percent more acidic, resulting in a pH that the oceans haven’t experienced for more than 20 million years.

The pteropod, or “sea butterfly”, is a tiny sea creature about the size of a small pea. Pteropods are eaten by organisms ranging in size from tiny krill to whales and are a major food source for North Pacific juvenile salmon. The photos below show what happens to a pteropod’s shell when placed in sea water with pH and carbonate levels projected for the year 2100. The shell slowly dissolves after 45 days. 

Ocean acidification is expected to impact ocean species to varying degrees. Photosynthetic algae and seagrasses may benefit from higher CO₂ conditions in the ocean, as they require CO₂ to live just like plants on land. On the other hand, studies have shown that a more acidic environment has a dramatic effect on some calcifying species, including oysters, clams, sea urchins, shallow water corals, deep sea corals, and calcareous plankton. When shelled organisms are at risk, the entire food web may also be at risk. Today, more than a billion people worldwide rely on food from the ocean as their primary source of protein.

SAHARA DESERT 

Saharan Africa suffers from chronically overburdened water systems under increasing stress from fast-growing urban areas. Weak governments, corruption, mismanagement of resources, poor long-term investment, and a lack of environmental research and urban infrastructure only exacerbate the problem. In some cases, the disruption or contamination of water supply in urban infrastructures and rural area has incited domestic and cross-border violence. Experts say incorporating water improvements into economic development is necessary to end the severe problems caused by water stress and to improve public health and advance the economic stability of the region.

Water stress refers to economic, social, or environmental problems caused by unmet water needs.
Agricultural development has the potential to improve African economies but requires extensive water supplies. These statisticsfrom the Water Systems Analysis Group at the Institute for the Study of Earth, Oceans, and Space at the University of New Hampshire reveal the urgent need for sustainable agricultural development:

• About 64 percent of Africans rely on water that is limited and highly variable;
• Croplands inhabit the driest regions of Africa where some 40 percent of the irrigated land is unsustainable;
• Roughly 25 percent of Africa’s population suffers from water stress;
• Nearly 13 percent of the population in Africa experiences drought-related stress once each generation.

To prevent this happening

Improved access to quality water is a long-term goal that requires more than humanitarian funds.

• Because sub-Saharan Africa is subject to more extreme climate variability than other regions, it needs improved water storage capacity. Some experts say that large dam projects would create a more sustainable reserve of water resources to combat the burden of climate fluctuations, but other disagree, stating the harmful environmental impact of large dams.
• Many experts say more water treaties are needed. Lautze says that transboundary water agreements have cultivated international cooperation and reduced the "probability of conflict and its intensity."
• Better donor emphasis on water development is needed. Giordano is concerned that global environmental issues are upstaging Africa-specific issues of water development.

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