Disturbing trends in the climatic condition of the Arctic led to scientists researching this area. Upon close scrutiny the fascinating greening of the Arctic has been observed. From the space, using Normalized Difference Vegetation Index (NDVI), which is an index of vegetation greenness, the circumpolar changes in the tundra vegetation are observed. The NDVI records of the last 29 years were gathered and the Maximum NDVI was derived. According to studies the MaxNDVI was usually observed in August due to many factors such as CO2 fluxes, above-ground biomass, total eco-system production etc. Many other biophysical properties also cause the MaxNDVI to increase during August. But recently the MaxNDVI of the tundra has increased substantially especially in Eurasia and North America. The main reason for this increase in arctic greening is related to the increasing summer warmth in the region.
Temperature Change around the World
Around the globe, temperature variation is observed, an average of 0.6°C increase in the earth’s surface has been observed over the last two centuries. The climatic change is mostly regarded due to human activities, especially due to combustion of fossil fuels. The increasing influx of greenhouse gases in the atmosphere is a major reason for temperature shift around the world.
The current rise in temperatures is affecting the Arctic regions severely. The average temperature in the Arctic is rising at a much faster, almost twice the speed than the rest of the world. These intense climatic conditions are bound to have severe consequences such as melting of the ice causing a rise in sea levels. ("Arctic Greening Linked to Retreating Sea Ice", 1)
Climate change in Tundra
Recent records state that the climate in the Arctic is increasing at a rapid stage. Increasing temperature has caused melting of glaciers, permafrost and sea ice, this in turn is increasing the sea level of the region. Alaska alone witnessed an increase in winter temperature. The following study is intended to understand the Arctic greening and its effects on the human race. The paper tries to understand the reasons behind the melting of the snow caps in Arctic and other physiological changes taking place in the region. Along with the help of studies and accumulated data, the following paper establishes the co relation between rising temperature and the changes taking place. As stated, global warming is the root cause of the rising temperature throughout the world and it is this problem that needs to be fixed at the earliest.
The climate change in tundra is expected to have many consequences, which could prove harmful. The growing change in temperature, season length and precipitation will affect the vegetation cover over the Arctic. If the Arctic keeps getting warmer, the vegetation cover of the Arctic will continue to rise. Increased greening will result in an imbalance of permafrost, thaw layer and the snow pattern. Apart from this, the wildlife will also be greatly affected. With regards to the climate, feedbacks to the climate trough variation in carbon flux and the amount of heat as well as light reflected will be observed.
According to studies the precipitation has increased by 8% throughout the region over the last 100 years. Apart from increase of precipitation, there has been a marked change in the precipitation characteristics. Most of the precipitation is coming down in the form of rains, which are observed during winters rather than the autumn or spring. Such increasing rain causes faster meltdown of the snow, and in case of heavy rains can result in flash flooding. Such events have increased significantly throughout Arctic. ("The response of Arctic vegetation to the summer climate: relation between shrub cover, NDVI, surface albedo and temperature", 2)
Expected Climatic changes in Arctic
In order to understand the potential climatic changes that could take place in future two main considerations are to be evaluated;
The levels of the greenhouse emissions
Response of climate to the emitted greenhouse gases
In order to project the levels of future emissions, plausible scenarios such as population growth, industrial growth, technological advances etc. are taken into consideration. Considering how the future society and energy is going to evolve, the climatic conditions can be predicted. Understanding the future trends, emission models are prepared using which the climatic changes are predicted. According to studies more global warming will affect the Arctic much more substantially than the rest of the world. The studies also show trends that the Arctic is likely to face much intense and early warming.
Studies also suggest that the by the end of this century, the average temperatures are set to rise across the entire Arctic. The rise could be 3-5°C near the land surfaces whereas the water surfaces can expect a rise of 7°C.
If the thresholds of the Arctic environment are crossed, it could lead result to considerable effects not just in the region but throughout the world. For example, the rise of 3°C during 21st century can cause the melting of the Greenland ice sheet which could result in the rise of the global sea levels almost by 7 meters
While there are many speculations regarding when the thresholds will be crossed, it is best to take precautionary measures before hand.
Albedo
The Arctic sea ice is a major deriver of world climate. Its changing conditions are directly responsible for the changing world climate. The albedo of the earth determines the global climate. It is the percent of sun’s radiation reflected back into the space, which consequently determine the cooling or heating of the earth’s surface. Recent studies have shown that the albedo of the Arctic region is rapidly losing due to the melting of ice. When the surface is light, the heat energy reflected is much more than darker surfaces that absorb the energy. As Arctic is surrounded by ice, its albedo was high, of almost85-90%. But due to the rapid ice melt, there has been an increase in shrub growth that is causing less reflection of heat energy, only 10-20% of heat is reflected back from such greening areas of Arctic.
Open waters too do not reflect back the energy; therefore the growing open water caused due to ice melt is causing less albedo that in turn is causing a rise in surface and air temperature. Such lowering of albedo is triggering higher ice melt due to increasing temperature.
Black soot
This is a major concern causing lowering of albedo in the Arctic. Black carbon emissions from the northern hemisphere are resting on the snow cap of the Arctic. This causes less reflection and hence rises in temperature. A research carried out by M.Jacobson in 201o revealed that global warming due to the black soot is second to that caused by CO2. He further dwelled on the prospects of reducing the Arctic temperature by almost 3°F within the next 15 years, if the back soot is controlled. ("Circumpolar Arctic Greening. Russian Academy of Science", 3)
Positive and Negative Feedbacks
There are many climatic mechanisms taking place which can either have a positive feedback, which could amplify the effects or a negative feedback, which could diminish the effects of the climatic changes. The future climate is highly dependent on the kind of feedback received.
One of the most important feedbacks of the climate is the ice and snow albedo effect. As discussed, higher concentration of ice causes more light reflection which in turn helps to lower the temperature in the Arctic. Whereas in warmer climate there is a decrease in snow cover, exposing larger expanses of water bodies and land surface that absorb solar radiation. This in turn contributes to accelerated increase in Arctic temperature. According to IPCC models, this increasing albedo feedback will result in decreasing snow cover by the 21st century.
The negative feedback constitutes of the cloud-radiative feedback. Due to the increased temperature in the Arctic, there is an increase in the cloud cover. This increase in cloud cover, even though results in increased reflection of solar radiation away from earth, it also causes the long-wave radiation which is emitted downwards on the earth surface from the clouds to increase.
Understanding both the positive as well as the negative feedback is important in order to suggest ways of controlling temperature increase in the arctic.
Sea Ice of Arctic
Sea ice is formed within water and melts away inside itself, unlike land ice such as glaciers and snow caps. When the water temperature dips below the freezing point, sheets of ice begin forming. On the formation of ice, salt is expelled which causes an increase in density. This is the major factor for deriving global ocean circulation. Apart from the sunlight factor, many other factors are now contributing to the melting of the sea ice in Arctic. Warm ocean current from the equator are causing the sea ice of Arctic to melt at a rapid rate. According to recorded data, the Arctic sea ice has decreased by 11% per decade. The more alarming aspect of this melting is the fact that rather than ‘new ice’, which is formed recently and is shallow, ‘multi-year’ ice is melting. ‘Multi-year’ ice is the kind which has survived from many years of sunlight melting and is hence very thick as well as stable.
A survey conducted in 2007 compared the multi-year ice to that in 1987. 57% of ice in that year was almost five years old whereas 25% was nine years old. In comparison, in 2007, merely 7%, whereas nine year old ice was not present at all and had melted away.
The sea ice in arctic is rapidly melting away with a decrease in the thickness as well as volume of the ice.
(Sea ice volume observations from PIOMAS (blue) and a simple mathematical function (orange) to fit the data and produce a forecast, which suggests the Arctic could be ice-free by the year 2030.
Shrub Growth
The recent arctic greening trends observed with the help of NDVI has shown an increase in shrub growth due to the rising temperatures. This increase in shrub growth is expected to cause a decrease in the summer albedo which could positively feedback to the climate warming.
Amongst the tundra vegetation, the deciduous shrub species such as Dwarf Birch, responds the most to the climatic changes. According to evidence, shrubs are the most responsible for the greening trend. Dendrochronological studies depict a drastic growth of willow in Siberia, which corresponds to local peak-summer NDVI as well as summer temperature. Consequently this shows the link between growth of shrubs, greening of the Arctic and the increasing air temperature.
Along with the increase in NDVI, increase in shrubs could cause higher absorption of short solar radiation which can help decrease the surface albedo and consequently lead to additional atmospheric heating (Chapin et al 2005, Euskirchen et al 2009). Alaskan shrub tundra has been witness to such kind of correlation between the shrub cover and the summer albedo.
Field observation
Upon investigation by various authorities, many insights have been developed that helps to understand the greening of Arctic. The Back to the Future (BTF) International project has carried out many researches in this order to gain better understanding of the vegetation and shrub development in the Arctic. Arctic research sites developed almost 15-18 years back were visited by researchers. Upon examination decadal-scale changes were observed. The changes included an increase in plant cover and vegetation especially in Barrow, Alaska and on the Baffin Islands. Multiple sites throughout Beringia also showed changing vegetation trends. The Disko Island in Greenland observed species shift and advanced phonological development. The sub-Arctic Sweden witnesses warming of the permafrost whereas Barrow faced drastic changes in the hygrophyte cover and chrionomid structure. Barrow sites also noted other changes such as increase in gross ecosystem production, methane efflux etc.
Even though air and the ground water warming is the primary reason for the changes taking place, other turbulences were also cause of change in some sites. In the herbivore enclosures in Barrow, the cover of lichens and graminoids had increased the shrub cover due to the herbivores and lemmings. Due to this increase in deciduous shrub cover, the ecosystem consisting of the methane efflux, NDVI, soil moisture, thaw depth, albedo etc. were all affected (Johnson et al. 2010). This should be taken as a warning about the changes that Arctic can cause in the species distribution and the biodiversity of the region. As these changes are something to worry about, the Circumpolar Biodiversity Monitoring Program is planning to launch a monitoring plan for understanding the changes in marine, land and freshwater ecosystem ("Trends in Arctic vegetation productivity 1982-2005 ",4 )
The Lemmings Effect
While the world remains indulgent in challenging the theories of scientists pertaining to the greenery in the Arctic, a separate sect of researchers have discovered and partly concluded that the foliage-burst in the Arctic may be a giving of lemmings. Researchers believe that the large populations of lemmings are transforming the Arctic landscape, as their herbivorous eating habits make them graze on plants and fertilize soils.
A team of researchers from the University of Texas at El Paso have been extensively studying and monitoring the environs of the Arctic. Their findings suggest that when lemmings are absent from the Arctic landscape, there is an increase in the growth of certain plant types called bryophytes and lichens.
However, in the presence of lemmings, the spread of grass and sedge – the actual staple diet of lemmings – seems to increase.
Researchers are quick to indicate that the advance populace of lemmings is not just good news for the ecosystem, but can positively influence changes in the climatic conditions.
Dr. David Johnson who is fronting the research and study strongly opines that the team’s findings confirm that greening of the Arctic cannot be and should not be seen as a by-product of global warming alone. Lemmings may be seen as the champions of greening the Arctic; however Dr. David is cautious of drawing final conclusions.
Images taken from satellite show the Arctic zone brimming with flora and fauna – grasses and shrubs – adding weight to the fact that the rising temperatures are making the Arctic area habitable. However, researchers are wary if this current phenomenon in the Arctic will cause global warming or cooling. The widespread of green matter in the Arctic could reduce global warming as the plants absorb large amounts of carbon dioxide. Another plus of this occurrence is that warmer temperatures benefit the soil – causing the soil microbes to respire and release into the atmosphere, influencing warmer climate.
The researchers are still wary of arriving at a definitive theory. The two feedbacks are distinct. A greener landscape can definitely provide a breeding ground for herbivores – and also help in evolving these areas to become carbon sinks.
Additional Effects
Apart from affecting the Arctic vegetation, many indirect changes are also observed such as the increase in thermokrast and fires as well as an increase in the number of landslides. The frequency of these calamities has increased in several regions in the Arctic. (e.g., Goosef et al. 2009; Lantz et al. 2010a,b; Mack et al. 2011 in revision; Rocha and Shaver 2011). Such disturbances also cause effects such as thawing thermafrost, increase in water, more nutrients, higher soil temperature etc. Such effects are conducive for abundant greening of the Arctic regions and it especially escalates the growth of shrubs. The increasing air as well as ground temperature is bound to increase the total shrub growth. This kind of artificial warming, even though minute and at a slower pace is proving to be harmful for the population residing in Arctic.
Conclusion
As observed from the above texts, it is an extremely dangerous trend that is becoming more and more rampant, as the earth’s surface and land temperature continues to increase. Human beings need to acknowledge the impending doom and make efforts to minimize the effects of global warming. It is important to realize that the fast melting of the snow caps will not only cause harmful effects to the habitants of the Arctic region alone, but instead will affect the world at large. The melting of the Arctic will result in the increase of the methane in atmosphere. According to studies in the year 2007 there was a substantial increase in Methane in the atmosphere. Along with that the atmospheric carbon is increasing at a very rapid state which is directly related to the thawing of the arctic ice.
The melting of the ice is causing an increase in the greenhouse gases present in the atmosphere. The vicious cycle can be extremely harmful for the environment as well as the entire human community at large. As the weather patterns shift, more prolonged floods and draughts are observed. The entire world economy is based on agriculture which in turn is dependent on the weather patterns. Therefore the rise in temperature, melting of the snow caps, thawing of ice, increased greening in the arctic are all factors that need immediate attention as well as action. Not merely from governments, but by the entire human race in order to fight the possible consequences of our own actions. ("Forest ecology and Management"5)
References:
1. Science Daily (2009). Arctic Greening Linked to Retreating Sea Ice. 17 December, 2008. Retrieved from web. http://www.sciencedaily.com/releases/2008/12/081217203316.htm
2. Blok D. (2011). The response of Arctic vegetation to the summer climate: relation between shrub cover, NDVI, surface albedo and temperature. http://iopscience.iop.org/1748-9326/6/3/035502/pdf/1748-9326_6_3_035502.pdf
3. NEESPI program (2009). 23 April 2009. Retrieved from web. http://neespi.org/web-content/meetings/AGU_2009/Walker.pdf
4. Ahlen us H. and Nordil (2012). Trends in Arctic vegetation productivity 1982-2005 (Greening of the arctic). 21 February, 2012. Retrieved from web. http://www.grida.no/graphicslib/detail/trends-in-arctic-vegetation-productivity-1982-2005-greening-of-the-arctic_ba52
5. Tommervik H. et al. (2009). Forest ecology and Management. 23 June 2009. Retrieved from web. http://www.arctichealth.org/ccChangingEcosystems
