Characteristics Of Sea Ice Motion And Deformation In The Arctic Using Sea Ice Motion Product

Sea ice moves in response to ocean currents,wind stress,and the Coriolis force,as well as due to the sloping sea surface and internal ice stress.Sea ice motion affects ice thickness distribution and also the energy and moisture budgets of atmosphere and ocean through sea ice advection and deformation.The measurement of sea ice motion by ice-tethered buoy is limited by the spatial-temporal coverage of buoy deployment.The development of satellite remote sensing has realized all-round and all-time observation of sea ice motion.Sea ice motion products derived from remote sensing data have been widely used in sea ice physical studies and data assimilation for sea ice or climate models.However,due to the difference of the data source and the tracking algorithm,there are large uncertainties in the sea ice motion products.The estimation of accuracy and uncertainty is necessary for the improvement and application of sea ice motion products.As Arctic warming amplification,sea ice in the Arctic,an important component of the global climate system,is changing rapidly,including its extent,thickness,physical characteristics,as well as the interactions with atmospheric and oceanic boundary layers.Investigating the temporal and spatial characteristics of sea ice motion in the Arctic will not only help to improve the understanding of the processes and mechanisms of sea ice change,but also be able to evaluate their implications for the evolution of Arctic sea ice and climate in the future.In addition,quantifying the effects of environmental factors,such as the atmospheric circulation patterns,on sea ice kinematic and dynamic processes is conducive to improving the understanding of the atmosphere-ice-ocean coupling mechanism,and it is also of great significance for the study of Arctic warming amplification and environment change.By using the ice-tethered buoy data,remote sensing products,and atmosphere reanalysis dataset,we focus on the Arctic sea ice motion and investigates the following aspects in terms of the accuracy of sea ice motion products,the temporal and spatial characteristics of sea ice motion,advection,and deformation,as well as the response of sea ice kinematics and dynamics to atmospheric circulation.(1)Validation and error estimation of two widely used sea ice motion products.Using the data collected by ice-tethered buoys deployed by the CHINARE cruises,we systematically evaluated the accuracy of the sea ice motion products from NSIDC(National Snow and Ice Data Center)and OSI-SAF(Ocean and Sea Ice Satellite Application Center).The ability of sea ice motion products to reconstruct sea ice trajectory and estimate deformation was assessed,and the spatial-temporal variabilities of errors were obtained.NSIDC product is proved to be more accurate than OSI-SAF product.Both sea ice motion products showed high accuracy in reconstruction sea ice trajectories in monthly scale,and the NSIDC product is also reliable for trajectory reconstruction in an annual scale.The error of deformation rate estimated using NSIDC products was relatively smaller compared to that using OSI-SAF data,and it could truly reflect the spatial scale properties of ice deformation.The influence of the magnitude of ice drift speed and concentration on the uncertainty of sea ice motion products was quantified.The error of NSIDC product is relatively more affected by changes in ice drift speed.However,OSI-SAF product is more sensitive to variations in sea ice concentration.(2)Analysis of spatial-temporal characteristics of sea ice motion and sea ice deformation in the Arctic.Based on the results of the validation of sea ice motion products,the NSIDC product was used to investigate the kinematic features of the sea ice from 1979 to 2018 in the Arctic.The long-term trend of sea ice drift speed was calculated,which proves that the Arctic sea ice drift speed has been continuously increasing in the recent 40 years.The spatial and inter-decadal changes in sea ice drift speed over the Arctic were analyzed.The sea ice drift speed increases significantly in autumn and winter.The increasing trend of sea ice drift speed in Beaufort Sea,Chukchi Sea,and Kara Sea was more obvious than in other regions.The effects of sea surface wind forces on sea ice drift speed were quantified.The response of sea ice motion to the changes in wind speed has weakened in the autumn of the western Central Arctic.The NSIDC sea ice motion products were applied to estimate sea ice deformation in the Arctic,and the time series and spatial heterogeneity of sea ice deformation rate in the Arctic Ocean were obtained.The sea ice deformation rate in the Arctic Ocean except for the Greenland and Barents seas has shown a significant increase during the freezing seasons from 1979 to 2018.The spatial scale and localization of sea ice deformation illustrate obvious spatial variability,and the localization of ice deformation in the western Central Arctic is larger than other regions.(3)Analysis of spatial-temporal variabilities of sea ice advection in the Arctic.Sea ice area flux was calculated to evaluate the sea ice advection and export in key sectors of the Arctic Ocean.The time series of sea ice advection and export area at the basin scale were obtained.From 1979 to 2018,the sea ice area advection between all sectors of the Arctic Ocean showed an overall increasing trend.The increase in the area of sea ice export from the northeast of Central Arctic to the Atlantic sector was the largest across the Arctic Ocean.The annual mean sea ice area exported from the Fram Strait to the Greenland Sea was 425×10~3km~2 with an increasing trend of 9.6×10~3km~2per year in 1979-2018.(4)The response of sea ice motion to atmospheric circulations in the Arctic.By using the atmospheric reanalysis data,the influence of atmospheric circulation indices,such as CAI(Central Arctic Index),DA(Dipole Anomaly),BH(Beaufort High),on sea ice advection and drift patterns were analyzed.From the nearly 40-year time scale,the BH has a more significant impact on sea ice advection in the Beaufort Sea than DA.The explanation level of the variations in the sea ice area export from the western Central Arctic to the Beaufort Sea in winter,spring,and summer was larger than 52%using the BH.Sea ice outflow through Fram Strait is more sensitive to change in CAI than for DA,and the explanation level of the summer CAI for sea ice outflow through Fram Strait was 36%.(5)Influence of sea ice advection in the Northeast Arctic on the accessibility of the Northeast Passage.By using the sea ice motion product,we quantify the impact of the northward advection of sea ice in the Northeast Arctic on the accessibility of the Northeast Passage.The characteristics of sea ice motion north of the Northeast Passage and the spatial-temporal characteristics of the sea ice advection in the Northeast Arctic were analyzed.The accessibility of the Northeast Passage in summer and autumn were analyzed using sea ice concentration product,and significant positive trends were observed in all sectors of the Northeast Passage in 1979-2018.By applying correlation analysis,it is found that the northward sea ice advection in spring has a significant impact on the open period of the Northeast Passage in summer and autumn,and the explanation level of each sector is higher than 35%.