Temporal And Spatial Variation Characteristics Of Bering Strait Throughflow Water And Its Influence On Sea Ice

The inflow water from the Pacific Ocean is transported northward through the Bering Strait,which has a significant impact on the marine environment and sea ice changes in the Arctic Ocean.The Pacific inflow has a fixed northward transport channel,and the heat it carries is the main reason for the melting of sea ice in Chukchi Sea.Moreover,the change of inflow water flow in the Pacific Ocean can lead to the change of its circulation path,thus affecting the transport and distribution of heat flux,and further affecting the temporal and spatial distribution of sea ice melting.At the same time,the velocity of the Pacific inflow affects the size and shape of the polynyas near the Bering Strait.Some previous studies have not reached a consensus on the contribution of atmospheric factors(including wind forcing and atmospheric pressure forcing on the sea surface)to the sea surface height difference,and the research on the circulation path of Pacific inflow in Chukchi Sea is not deep enough,and there is little research on the distribution relationship between the position change of each path and the flow of each branch due to the increase of inflow water.In this paper,the regional model AO-FVCOM of Arctic Ocean is constructed by using unstructured finite volume ocean model FVCOM,and the model data results are verified based on the mooring observation data of Bering Strait and Chukchi Sea.The circulation path of Pacific inflow water in Chukchi Sea is explored by particle tracking experiment,and the variation characteristics of volume flux of 12 sections in the circulation path of Bering Strait-Chukchi Sea are analyzed.On this basis,this study comprehensively analyzes the main influencing factors of Pacific inflow in the first 20 years of the 21 st century(2001-2020),and quantitatively studies the atmospheric factors such as sea level pressure and wind field that affect the sea surface height difference,thus deeply understand the driving mechanism of multi-factor interaction of Pacific inflow.In addition,the Bering Strait throughflow water influences the formation and melting of sea ice in Chukchi Sea.This paper further discusses the spatial distribution characteristics of sea ice in Chukchi Sea under the influence of the inflow of Bering Strait.The model shows good results in simulating the data of velocity,volume flux and sea level anomaly.In terms of velocity,the average velocity of observation and model data is in the range of 8-40 cm/s,with an absolute error of 9.3 cm/s and an absolute error of 30.This shows that the velocity simulated by the model is highly reliable.Secondly,the average volume flux of Bering Strait estimated based on the velocity of A2 and A3 stations is 0.90 ± 0.11 SV and 0.96 ± 0.11 SV,respectively,and the volume flux calculated by the model is 1.07 Sv.In addition,for the sea surface height anomaly data,the observed and model sea surface height anomaly data in the study area are all between 0-8 cm,with a root mean square error of 4.47 cm,and its correlation coefficient can reach 0.87 in the Bering Strait area.The model well simulates the three tributaries of the Bering Strait inflow into the Chukchi Sea,namely Alaska coastal current,Bering Sea shelf water and Anadel water.Through the analysis of the volume flux of 12 sections,we find that the growth of inflow water in Bering Strait has the most obvious influence on Alaska coastal current,and more eastern tributaries develop westward and enter the Arctic Ocean when passing through Barrow Canyon.There is a high positive correlation between the volume flux of the Bering Strait and the sea surface height difference between the upstream and downstream of the Bering Strait,and the correlation coefficient can reach 0.98.The increase of sea surface height difference between the upper and lower reaches of Bering Strait is determined by the change of sea surface height in the upper reaches.The decrease of sea surface height difference is determined by the change of sea surface height downstream.Through sensitivity experiments,it is found that the volume flux generated by sea level pressure by adjusting the sea surface height difference is relatively large.Because of the small change of sea level pressure,the sea surface height difference is relatively stable,resulting in a relatively stable change of volume flux,which indicates that the sea level pressure provides the basic quantity of volume flux in the Bering Strait.In most months,the volume flux generated by the wind field has a higher correlation with the original volume flux simulated by the model(wind field and pressure acting together),indicating that the characteristics of volume flux changing with time are mainly regulated by the wind field.Seasonal wind field can lead to seasonal variation of volume flux.From April to August,the wind speed increases and the volume flux decreases;From September to March,the wind speed decreases and the volume flux increases.Compared with 2001-2005,the sea level pressure in the Bering Strait decreased from April to August in 2006-2020,which caused the sea surface height to rise.Due to the Coriolis force,the northwest wind caused the upstream sea water to diverge and the downstream sea water to converge,which caused the upstream sea surface height to drop and the downstream sea surface height to rise,which led to the decrease of the sea surface height difference between the upstream and downstream.During the three months from September to,the atmospheric pressure on the sea surface in the study area increased,which caused the sea surface height to decrease.Due to the southeast wind,the upstream sea water converged and the downstream sea water diverged,which led to the elevation of the upstream sea surface height,the elevation of the downstream sea surface height decreased,and the elevation difference between the upstream and downstream sea surface heights increased.The months of sea ice melting in Chukchi Sea mainly occur from May to August,and the most significant area of sea ice melting is consistent with the transport path of inflow water.There is a one-month lag between the heat carried by the inflow water and the melting of sea ice in Chukchi Sea.In brief,the flow velocity in the eastern and central parts is faster.