Statistics And Characteristics Of The Last Permafrost Maximum In The Northern Hemisphere

Since Last Glacial Maximum, climate on earth has taken place great changes. Temperature increasing and amount of carbon increasing in the atmosphere are two important features. Last Permafrost Maximum ever expanded southward widely, and it is an urgent problem to be solved that what extent permafrost distributed to from the perspective of the northern hemisphere. At the same time, permafrost degradation appeared in large scale after entering Megathermal. A variety of studies showed that permafrost degradation’s positive feedback effect on atmospheric temperature is not be neglected. At present, permafrost has preserved a large number of carbon, which is two times more than that in atmosphere. How much carbon will be released into atmosphere during the process of permafrost degradation, increasing of atmospheric carbon contributing to increasing of global temperature and the extent of permafrost degradation all are the new research hotspot in the field of permafrost and climate change.This study collected many maps palaeopermafrost distribution in permafrost regions, maps of ancient ice sheet, boundary of continuous and discontinuous palaeopermafrost and residual permafrost data through the help of northern hemisphere permafrost mapping group of International Permafrost Association (IPA), combining barren land in Last Glacial Maximum and modern altitude data extracted by DEM and the high resolution Last Permafrost Maximum Map. Utilizing these map data to calculate permafrost distribution characteristics in the Last Glacial Maximum and the comparison of palaeopermafrost distribution and modern permafrost under different situations. Meanwhile, we can also get the permafrost degradation area and features since Last Glacial Maximum. What should be explained is that this map has certain limitations. For example, residual permafrost data is not very accurate; boundary of continuous and discontinuous permafrost only be marked out at low altitude area, but not noted at high altitude area because of many complicated factors. With the discovery of new fossil periglacial phenomena, this map is temporary and instant-renewal.This paper presents an area of palaeopermafrost distribution and statistics based on the latest version of the map:In general, a total area of the Last permafrost Maximum is about 50.32×106m2 (including the land under ice sheets), Eurasia accounts for two-thirds of them, and LPM area accounted for 52.77% of the land area of the northern hemisphere; In mainland area during the LGM, the LPM area was about 58.03×106Km2; the Last Glacial ancient ice sheets area was 21.344 × 106km2, divided into four regions. The LPM distribution was:The permafrost has been widely distributed in the northern hemisphere, the non-alpine zone of the northern hemisphere north of 45°N region basically belong in LPM regions, while in eastern of China it’s up to 37° N. The low limit of mountain permafrost was between 1000m～2000m, The low limit of permafrost in North America is slightly higher than Tibetan Plateau. On the latitudinal distribution there has three peaks, at 30°-40° N,45°-48°N and near 66 °N; 90°E and 90°W is the largest area of palaeopermafrost distribution as modern permafrost, The difference between the two peak values than modern small; at an altitude Distribution palaeopermafrost region mainly at an altitude of 1000m, but 2000～5000m distributed more than modern permafrost tundra area. Study found that degradation of permafrost, permafrost area was reduced by about 27.53×106km2, this area was more than the modern permafrost zone 4.74 × 106km2; subsea permafrost area is estimated to be:6.85 ×10km2, and the relict permafrost area (excluding subsea permafrost) is between 9.4-9.9 × 106km2. LPM most serious degradation in Europe, close to the southern boundary from 45°N degradation north to Scandinavia, degradation margin of 15 to 22 latitude; distribution of low limit of palaeopermafrost in the Tibetan Plateau and mountain regions of Central Asia the 1500-2000m increased to about 3500-5300m; LPM in the eastern region Chinese degraded area is relatively small, by the Qinling Mountains- the Yellow River line back to northern Heilongjiang for a generation and it’s about 8 latitude around; most of the northern part of North America was covered by ice sheets,, LPM degraded relatively uniform gradient of a good degradation and margin of 8 to 15 latitude. This is similar to results of previous studies, but t greater change of the magnitude.The results summarized the distribution characteristics and area analysis of Last Permafrost Ma ximum in the Northern Hemisphere, which providing data support for estimating the amount of ca rbon releasing of permafrost degradation. This study is also a synthesis of former researches and d escribes and analyses Last Permafrost Maximum from place to place in a larger scale. The next stu dy is to explore the relationship between palaeoclimatic changes and Last Permafrost Maximum degradation. According to modern permafrost carbon density, related data of IPCC and the area of permafrost degradation, we could obtain the contribution of carbon emission increasing from perm afrost because of permafrost degradation to atmosphere carbon increasing roughly since the Last Glacial Maximum.