Climate Change Associated with Global Teleconnections, Volcanic Eruptions, and the Arctic’s Snow-Ice Albedo in Godthab, Greenland ()
1. Introduction
Climate change, as defined by the Intergovernmental Panel on Climate Change (IPCC), is any change in the climate over time, whether due to natural variability or as a result of human activity [1]. The Arctic is viewed as an amplifier of climate change because of the feedback effects associated with its high albedo of snow and ice, low precipitation, and low temperatures. Not only is the Arctic’s climate change amplified, it also experiences an early-onset of climate change symptoms [2]. The observed climate changes experienced by Greenland, located in the high Arctic, will offer great insight into the extent of global warming thus far. The study is especially important because the effects of climate modes, volcanic eruptions, and human activities can have large impacts on Godthab’s annual and seasonal temperature and precipitation, which in turn can impact ice sheet extents and sea level rise. Greenland is 82 percent covered by ice; therefore, a long warming period could initiate significant melting and conclude with significant sea-level rise [3].
High latitude climates, like Godthab’s, experience long periods of continuous sunlight in the summer and a period of perpetual darkness in winter. High latitudes are very reflective due to the high albedo of their predominant ice and snow cover. By reflecting its limited solar radiation back into space, the land and water surfaces retain their cold temperatures. The ice-albedo feedback is the most significant positive feedback influencing polar regions, and is thought to have been the cause for the recent, large changes observed within the Arctic [2,4]. A slight increase in temperature within the Arctic can setoff a pattern of events leading to continual decrease in snow and sea-ice, and continual increase in temperature. By increasing the regional temperature, and melting snow and sea-ice, the ground’s albedo is decreased, and is better able to absorb solar radiation and further warm the Arctic climate.
Precipitation is greatly influenced by a region’s temperature because air at cold temperatures has a reduced water capacity; therefore, Polar Regions receive limited precipitation. Godthab’s limited precipitation exemplifies this high latitude relationship. The lowest global precipitation occurs within the plateau of Antarctica and in the central area of Greenland [2], which is proximal to Godthab.
Another determinant of climate change is aerosols. The Arctic is especially susceptible to the effects of aerosols in the atmosphere; mid-latitude aerosols are transported pole-ward from source regions. Aerosols from anthropogenic processes and volcanoes are the most influential on the climate. The two aerosols emitted by volcanoes that have greatest impact significance on Greenland are dust and gaseous sulphur (SO2). Sulphur from volcanoes, depending on the eruptive strength of a volcano, can inject their aerosols past the troposphere and into the stratosphere where they have a longer residence time, and can be dispersed further. The Volcanic Explosive Index (VEI) is used to quantify a volcano’s intensity between one and six. A mid-latitude volcano, with a high VEI, can cause significant cooling for years after an eruption. This cooling phenomenon is strongest in the winter season [5].
Section 2 describes the study site. Sections 3 and 4 outline the climatology for the two periods (1866-2011) and (1985-2011). Section 5, presents the climate modes and their effect on temperature and precipitation of Godthab. Section 6 finishes with discussion and conclusions.
2. Study Site
Godthab (locally known as Nuuk) is located within the subarctic along the west-coast of Greenland at 64˚20'39'' North (latitude), 51˚34' West (longitude), and an elevation of 70 m above sea-level. Godthab is the capital of Greenland. Based on its location proximal to the Icelandic low, the North Atlantic Oscillation (NAO) and Arctic Oscillation (AO) are anticipated to play a significant climatic role. Due to the high latitude of Godthab, all climate considerations must account for the seasonal fluctuation of insolation. Godthab is located within a subarctic to arctic climate; cool summers and cold winters.
3. Climatology (1866-2011)
3.1. Temperature
The annual average temperature of Godthab has increased by 1.9˚C and had a mean temperature of −1.3˚C over the past 146 years, from 1866 to 2011 (Figure 1). It shows a moderate temperature trend with a correlation coefficient of 0.3. After a large volcanic eruption, such as in 1883, 1912, 1980, and 1991, Godthab continually experienced a cooling period that lasted up to three years. The greatest cooling periods occurred in the early 1880s, early 1980s, and early 1990s, after either a single volcano
Figure 1. Annual average (solid line) and average winter (dotted line) temperatures from 1866-2011, with notes of significant volcanic eruptions (over VEI 5), and arrows noting years of big ENSO events. Solid arrows are El Niño events (1982/83, 1986/87, 1997/98, and 2010), and the dashed arrows are La Niña events (1988/89 and 1998/99). The effects of volcanic eruptions, reducing the temperature in subsequent years, can be clearly seen; 1883’s Krakatau (Indonesia), 1886’s Mount Tarawera (New Zealand), 1902’s Santa Maria (Guatemala), 1907’s Ksudach (Russia), 1912’s Novarupta (Alaska, US), 1932’s Cerro Azul (Chile), 1956’s Bezymianny (Russia), 1980’s Mount St. Helen’s (Washington, US), 1982’s El Chichón (Mexico), and 1991’s Pinatubo (Philippines).
with a VEI of 6, or multiple volcanoes with a VEI of 5+ (Figure 1). The annual temperature range was 29.6˚C during the 146 years, with the maximum temperature in 1936 (9.8˚C) and minimum temperature in 1984 (−19.6˚C). Interestingly, in contrast with the trends of many North American cities, Godthab has not experienced most of their significant warming recently; in fact, the majority of their warmest years are prior to 1986 (Figure 1). The only exception was 2010, with an average annual temperature of 2.6˚C, earning the year a position as the hottest annual average on record, and also as one of the top three hottest years for all seasons (Table 1). Two large warming periods occurred since 1866, they were 1919- 1937 and 1993-2010. Both warming periods coincide with periods of large (VEC = 6) volcanic eruption absence [5,6].
Figure 2 shows the temperature fluctuations experienced in Godthab for the 10-year averages. Unlike many northern hemisphere cities that have experienced a steady temperature increase in the past century, Godthab’s climate experienced a drop in temperature between 1966 and 1995. The declining period, and the significantly lower temperatures from the mid-1980s until the mid1990s are illustrated in Figures 1 and 2. Further research was required into climate modes to determine the reasoning for this temperature anomaly.