The Last 1.5Ma Record Of Sea Surface Temperature And Its Environmental Significance Of Site U1312 In The North Atlantic

The North Atlantic is the starting point of global ocean circulation,the engine of global temperature and salt cycle,and is very sensitive to global climate change.U1312 station is located in the middle latitude of the North Atlantic,which can actively respond to the development of the Arctic ice sheet and the characteristics of climate change.Therefore,the reconstruction of the surface water paleotemperature in the study area since 1.5 Ma is of great significance for the study of the Arctic ice sheet fluctuation and the climate change caused by it.In this paper,the sea surface temperature?SST?of the study area since 1.5 Ma has been obtained for the first time by measuring the Mg/Ca ratio of the shell of planktonic foraminifera G.ruber in the surface sediments of U1312 core?42°50?N,23°5.2?W?in the North Atlantic.On this basis,combined with other research data such as foraminiferal shell ???18?O of the station,and compared with other core data of the North Atlantic,the change of SST in the study area since 1.5 Ma and its response to the growth and decline of the Arctic ice sheet are discussed.The results show that the SST change curve of U1312 station since 1.5 Ma shows obvious glacial interglacial cycle characteristics,and the overall temperature shows a downward trend.The SST change range is 11.94??21.09?,and the lowest temperature is now MIS12?478?424 kaBP?.According to the fluctuation of?¹⁸O and SST of foraminiferal shell in the study area,it can be inferred that the Middle Pleistocene transition took place from about 961kaBP?MIS25?to 660kaBP?MIS17?,and the climate dominant cycle gradually changed from the slope cycle dominated by41ka to the eccentricity cycle dominated by 100ka.Compared with the core data of different stations in the North Atlantic,it is found that the study area was mainly affected by the North Atlantic Current?NAC?about 1Ma ago,showing relatively warm climate conditions?average temperature 16.92??.After the Middle Pleistocene transition,the duration of the ice age increased and the temperature was low?average temperature:15.36??,but SST recorded that there was no extreme cold event in the ice age of MIS16?minimum temperature:14.83??and MIS14?minimum temperature:14.86??compared with the high latitude area,indicating that the Arctic front?AF?was in a higher latitude position.In MIS10?8,large-scale IRD input occurred in the study area,and extreme events with a small number of abnormal dominant warm species G.ruber occurred,which led to the lack of continuity of relevant data.The low SST?minimum temperature:11.94?,maximum temperature:13.9??and high content of IRD input events in the period from MIS12 to the last glacial period indicate that during this period,the cold glacial melt water input affected the surface water temperature of the study area,and the east of the North Atlantic was affected by the strong AF which was too far to 37°N during the glacial period,while the glacial melt water input weakened the North Atlantic thermohaline circulation and hindered the NAC moved to the high latitudes of the North Atlantic,which made the North Atlantic region cool further.