| Global warming, land desertification and a series of environmental problems are attracting more and more attention in recent years. As the background event of global warming, Little Ice Age is always concerned by many researchers. Being the latest stage of global climate system without apparent human impact, with various record types wide distribution and high resolution, it could provide a time window for inspecting global climate system oscillation characteristics to predict future climate change, which has realistic significances on future global change research and climate predication. Predecessors study Little Ice Age mainly through stalagmites, lacustrine deposits, ice core, tree rings, history records and so on, aiming to reveal summer monsoon and its relevant indicated information. However they relatively lack winter monsoon evolution information, especially on the Mid-Lower Reaches of Yangtze River.Po-yang Lake basin lies in east-Asia monsoon humid area where winter monsoon is extremely strong; frequent strong winds blow and pit the bare floodplain of Yangtze River and Ganjiang River, then regional sandy accumulation physiognomy——longitudinal dune formed. Granularity analysis reveals that the frequency curve of the longitudinal dune's sandy deposit has three frequency distribution in um (namely three dependent kurtosis). The middle gran size of the first totality of frequency distribution in um(in the crude gran side) represents the strength of near-ground airstream namely the strength of winter monsoon. About 60-year meteorology data of Nanchang area shows that winter monsoon change of Poyang Lake in North Jiangxi is consistent with East-Asia monsoon strength change, from which we can see winter monsoon change of Poyang area is sensitive to global climate change.This paper firstly discusses Bo-touli profile in Xing Zi county revealing the characteristics of nearly 180-year high-resolution winter monsoon evolution in Late Little Ice Age(about 1670-1850), we found winter monsoon is highly sensitive to solar activity and volcano activity through compared . Secondly consulting plenty of Jiangxi Province chorography, The record of Qing Dynasty, Brief History of Jiangxi and some historical information, the author do some statistics about flood-drought events, ice-snow events, cultivated land quantity change, measures to disasters by the country and local government, peasant uprisings and some historical information then compare environmental information with historical information, some conclusions are drawn:1. The granularity indicators of Bo-touli profile deposits have a good response to macula activities record and D.V.I record. Within error range there exist two following phenomenon: 1) in the minimum period of macula, winter monsoon strengthens, otherwise winter monsoon weakens; 2) in early period of Dalton Minimum corresponding to the intense stage of global volcano activity, winter monsoon is in a special strong period, that is to say the cold period (about1810-1820) tends to be very marked.2. The winter monsoon evolution feature of Po-yang area from 1670±20 to 1850±20 can be divided into three times: A) winter monsoon is weak form about 1670±20 to 1720±20, but in the background of relatively weak winter monsoon there exist several extremely strong winter monsoon events; B) about 1720±20 to 1800±20 is a weak stage of winter monsoon climate and winter monsoon is wholly weak. Strong winter monsoon activities weaken and lessen apparently; C) winter monsoon is relatively strong from 1800±20 to 1850±20 and this stage can be divided into two sub-stages: about 1800±20 to 1820±20, winter monsoon turns weak from strong; about 1820±20 to 1850±20 winter monsoon begins to turn weak and in around 1850±20 this cold period tends to end.3. DM period can be divided into three stages. The first stage is about1790-1800 which is early DM period as well. At that time winter monsoon started to strengthen and tended to be cold-wet. The second stage is from 1801 to 1810 which is also middle DM period, indicating that it turned a little warmer than the former stage and tended to be warm-dry. The third stage is about 1811-1830 when it started to get cold and was entirely cold-wet except several dry years.4.The temporal distribution of flood-drought events and ice-snow events in DM period of Jiangxi province has a good response to this area's winter monsoon change. Ice-snow disaster happens when cold period happens correspondingly, what's more, flood disaster is more sensitive to winter monsoon than drought disaster. The government would consciously relief the victims, postpone or free the imposition tax, reclaim wasteland and take some other measures. Disasters caused by natural calamities are an important reason of peasant uprisings. |
