Air temperature changes until now

Iceland enjoys a warmer climate than its northerly location would indicate because a part of the Gulf Stream flows around the southern and western coasts of the country. Reykjavik has a cool temperate climate; with mean annual temperatures similar to cities nearly 20° of latitude farther south like Toronto or New York. This is not to say that it never gets cold in Reykjavik, because it does.

In addition, the result of mixing the warm, moist Atlantic air with the cold, dry Arctic air produces a weather pattern that is wrought with instability. The mean annual temperature for Reykjavik is 5°C, with the average January temperature being -0.4°C and July 11.2°C. The temperature records for Reykjavík are 24.8°C (76.6°F) on August 11, 2004 and -24.5°C (-12.1°F) on January 21, 1918 (1).

Reykjavik’s climate is controlled by the battle between bitterly cold arctic air masses from the Arctic, and the influx of warm air and water provided by the North Atlantic Current. The island of Iceland lies within the warm North Atlantic Current which is the northern extension of the Gulf Stream Current. A branch of the North Atlantic Current, the Irminger Current, flows around the southeast side of Iceland, greatly moderating Reykjavik’s climate. By contrast, the northeastern side of Iceland is dominated by the East Icelandic and East Greenland currents, which are cold currents flowing southward from the Arctic. In general this causes cooler temperatures in the northeastern sections of Iceland than are found in the Reykjavik area. Seasonal sea ice flows from Greenland are also responsible for cooling in the northern sections of Iceland (1).

The Icelandic Low, which is a semi-permanent area of low pressure residing over the northeastern Atlantic Ocean, also has a great effect on the climate of the region. It tends to draw warm air from the south into the arctic on its eastern side, and cold air from the arctic to the south on its western side. This contrast in temperature coupled with the contrast between oceanic currents is conducive to the formation of fronts and storm systems. This proclivity for stormy weather causes a high annual precipitation for Reykjavik. The Icelandic Low is part of the North Atlantic Oscillation (NAO) along with the Azores High. The NAO is the change in pressure difference between both pressures systems (1).

In the 1920s there was a period of rapid warming, similar to what is observed in global averages, but in Iceland the temperature change was greater and more abrupt. From the 1950s temperatures in Iceland had a downward trend with a minimum reached during the Great Salinity Anomaly, when sea ice was prevalent during late winter along the north coast. Conditions were rather cool in the 1970's with 1979 being the coldest year of the 20th century in Iceland. Since the 1980's, Iceland has experienced considerable warming, and early in the 21st century temperatures reached values comparable to those observed in the 1930s (2).

From 1975 to 2008 the warming rate in Iceland was 0.35°C per decade, which is substantially greater than the globally averaged warming trend (~0.2°C per decade). However, the long term warming rate in Iceland is similar to the global one, suggesting that the recent warming is a combination of local variability and large scale background warming. In Reykjavík 2009 was the fourteenth consecutive year with temperatures above the 1961 - 1990 average and the 9th consecutive year warmer than the 1931 - 1960 average (2).

Precipitation changes until now

Storms and rain are frequent, with average annual precipitation ranging from 400 to 4000 mm, depending on location (2). The annual precipitation on the south coast is about 3,000 mm, whereas in the central highlands it drops to 400 mm or less. Reykjavik has precipitation 213 days per year, with the spring being slightly less unsettled. Generally precipitation falls as rain even in the winter, but an occasional snowstorm is not uncommon. Reykjavik and other coastal areas in Iceland tend to be windy and gales are common, especially in winter, while thunderstorms are extremely rare (1).

Glacier changes until now

Europe’s largest glaciers are in Iceland, where they cover about 10% of the landmass (4). Iceland’s southeast glaciers on the southern edge of the Vatnajökull ice cap are located in the warmest and wettest area of Iceland (5) and therefore respond quickly to changes in temperature and precipitation. Since the start of this millennium, the southeast outlet glaciers of Vatnajökull have retreated rapidly; their mass loss per unit area is among the highest in the world (6). One of the glaciers in this area, Breiđamerkurjökull, has retreated more than 5 km, losing 11.2% of its volume from the late 19th century to 2010 (7). Current annual average retreat of this glacier is about 96 ±9 m) and surface lowering (3.5-6 m) (8). 

Air temperature changes in the 21st century

To the end of the 21st century the warming rate is projected to be 0.16-0.28°C per decade, yielding a warming of 1.4-2.4°C at the end of the century, based on the results of the climate models used in the IPCC AR4 report (2007) and different IPCC SRES scenarios. The warming in Iceland exhibited in the IPCC climate models is somewhat lower than the warming rates realized in Iceland in recent decades. This fits with the view that the recent warming is in part a local natural temperature change, superimposed on a large scale global warming signal (2).

Climate projections for southeast Iceland show an increase in annual temperature of 2-2.4°C under an intermediate (RCP 4.5) and 3.4-4°C under a high-end (RCP8.5) scenario of climate change by 2081–2100 (10).

Precipitation changes in the 21st century

Precipitation is projected to increase on average by 2% - 3% by the end of the 21st century (11). The uncertainty range is quite large, though.

Wind climate changes in the 21st century

Climate model projections do not show a significant change in wind near Iceland (2).

Impacts on glaciers in the 21st century

Glaciers are a distinctive feature of Iceland, covering about 11% of the total land area. The largest glacier is Vatnajökull in southeast Iceland with an area of 8,200 km2 (2).

Climate changes are likely to have a substantial effect on glaciers and lead to major runoff changes in Iceland. Changes in glacier runoff are one of the most important consequences of future climate changes in Iceland. The expected runoff increase may, for example, have practical implications for the design and operation of hydroelectric power plants (2).

The picturesque Snæfellsjökull ice cap is the only ice cap that can be seen from Reykjavík. It has persisted for many centuries, at least since Iceland was settled in the ninth century AD, but recent measurements show that the ice cap, which has an average thickness of less than 50 m, thinned by approximately 13 m in the last decade. At the current rate of thinning it will disappear within the century (2).

Modeling of the Langjökull and Hofsjökull ice caps and the southern part of the Vatnajökull ice cap in Iceland reveals that these glaciers may essentially disappear over the next 100-200 years. Runoff from these glaciers is projected to increase by about 30% with respect to present runoff by 2030. The peak runoff is expected to occur in the latter part of the 21st century (2). Glacier models indicate that the glaciers at the southern Vatnajökull ice cap could lose around 25% of their current volume within the next 50 years (9).

Changes in the Arctic

Over the past 30 years, the annual average sea-ice extent has decreased by about 8%, or nearly 1 million square kilometers, an area larger than all of Norway, Sweden and Denmark combined, and the melting trend is accelerating. Sea-ice extent in the summer has declined more dramatically than annual average, with a loss of 15-20% of the late-summer ice coverage. Sea-ice has also become thinner in recent decades, with arctic-wide average thickness reductions estimated at 15-20% (3).

Arctic precipitation has increased by about 8% on average over the past century. Much of the increase had come as rain, with the largest increases in autumn and winter. Over the Arctic as a whole total annual precipitation is projected to increase by roughly 20% at the end of this century, with most of the increase coming as rain (3).

Snow cover extent over arctic land areas has declined by about 10% over the past 30 years, and model projections suggest that it will decrease an additional 10-20% before the end of this century. The reduction will be especially strong in Scandinavia and Northwest Russia (3).

Arctic temperatures have risen about twice the rate as elsewhere in the world in the past few decades. The Arctic warms faster than lower attitudes for several reasons (3):

• as arctic snow and ice melt, the darker land and ocean surfaces that are revealed absorb more of the sun’s energy, increasing arctic warming;
• in the Arctic, a greater fraction of the extra energy received at the surfaced due to increasing concentrations of greenhouse gasses goes directly into warming the atmosphere, whereas, in the tropics, a greater fraction goes into evaporation;
• the depth of the atmospheric layer that has to warm in order to cause warming of near-surface air is much shallower in the Arctic than in the tropics, resulting in a larger arctic temperature increase;
• as warming reduces the extent of sea ice, solar heat absorbed by the oceans in the summer is more easily transferred to the atmosphere in the winter, making the air temperature warmer than it would be otherwise;
• because heat is transported to the Arctic by the atmosphere and oceans, alterations in their circulation patterns can also increase arctic warming. 

Integrated over the year, incoming energy from the sun is greatest near the equator and smallest near the poles. Further, because most of the Arctic is covered with snow and ice, a larger fraction of the incoming solar energy is reflected back to space than at lower altitudes. If not for the atmosphere and oceans moving energy from the tropics to the poles, the tropics would overheat and the polar regions would be much colder than they are. In the Northern Hemisphere, the Atlantic Ocean is the major carrier of the oceanic component of this energy transfer (3).

There are three major mechanisms, or “feedbacks”, by which arctic processes can cause additional climate change for the planet. One involves changes in the reflectivity of the surface as snow and ice melt and vegetation cover changes, the second involves changes to ocean circulation as arctic ice melts, adding freshwater to the ocean, and the third involves changes in the amounts of greenhouse gasses emitted to the atmosphere from the land as warming progresses. The ocean circulation is called a thermohaline circulation (thermo = heat, haline = salt), and is driven by differences in heat and salinity (3).

Projected temperature change based on the calculations in this report from 1990s to 2090s: average annual temperature increase of roughly 3-5⁰C over the land areas and up to 7⁰C over the oceans. Winter temperatures are projected to rise significantly more, with increases of 4-7⁰C over the land areas and 7-10⁰C over the oceans (3).

References

The references below are cited in full in a separate map 'References'. Please click here if you are looking for the full references for Iceland.

1. Nowotarski et al. (2006)
2. Ministry for the Environment of Iceland (2010)
3. ACIA (2004)
4. Björnsson (2017), in: Welling et al. (2019)
5. Hannesdóttir et al. (2010), in: Welling et al. (2019)
6. Hannesdóttir and Baldursson (2017), in: Welling et al. (2019)
7. Guđmundsson et al. (2017), in: Welling et al. (2019)
8. Welling et al. (2019)
9. Björnsson and Pálsson (2008), in: Welling et al. (2019)
10. Icelandic Meteorological Office (2017), in: Welling et al. (2019)
11. Icelandic Ministry for the Environment and Natural Resources (2018)