Using Multi-source Observation Data To Analysis Of The Causes Of The Accelerated Rise Of Global Mean Sea Level Since 2011

Sea level is a key indicator of global climate and environmental changes,and is deeply influenced by human activities,climate change and environment changes.The rise of sea level poses a huge threat to the socio-economic development of humankind,so,detecting and analyzing sea level changes and preventing this potential threat have been topics of concern to all countries in the world.Sea level change is the result of global warming,ice melting and sea-land water exchange.The altimetry data shows that the rate of Global mean sea level(GMSL)began to accelerate since 2011 after experiencing a period of rate slowdown from 2002 to 2010.Thus,it is very important to study and analyze the causes of the accelerated rise of GMSL in recent years.In this paper,with the help of GRACE data and other multi-source observation data,the causes of the accelerated rise of GMSL in recent years are discussed in detail from,sea level change,ice melting and land water change(including human-driven and natural-driven).The main research work and contributions are as follows:1.GRACE time-varying signal recoveryIn the view of the phenomenon of time-varing signal weakening and leakage in the process of GRACE data processing,the scaling factors method,the forward modeling method and the space domain inverse method are mainly introduced.The recovery results of several inverse methods are analyzed and compared in detail.The result shows:1.The scaling factors method is relatively simple to implement,but the inverse result completely depends on the selected prior model.When the reliability of the selected prior model is poor,the signal recovery effect will be affected.2.Restoration process of forward modeling method is constrained by the original GRACE observations,and can restore the long-term trend signal and periodic signal,effectively remove the signal leak from land to ocean,it is particularly suitable for restoring ocean signals.3.The space domain inverse method needs to divide the mascons according to geographical or quality feature points.The solution involves a large number of parameters and needs regularization.Thus,it is only applicable to the signal recovery of the local area feature points and does not apply to the global time-varying signal recovery.2.Sea level change analysisWe use altimetry,GRACE and Argo data to obtain a good GMSL change estimate.The rate of GMSL obtained from mass(GRACE)+ steric(Argo)is 3.24±0.18mm/yr during 2005-2015,which is close to the altimetry observed results(3.40+0.19 mm/yr).we use four different time series fitting strategies to analyze the sea level changes.The results show that the rate of GMSL in 2011-2015 is nearly 132%higher than that in 2005-2010.ENSO has a significant impact on sea level changes,which can explain 88%of the non-trendy interannual change signal of GMSL in 2011.3.The sea level budget estimateWe further to isolate the factors influencing ocean mass change.Our estimates of sea level budget and altimetry observations have a high degree of agreement before 2014,but after 2015 there is no good match.Which,we believe,is caused by a deterioration of GRACE data observations after 2015 Through time-series weighted optimal estimation,we obtain a better sea-level budget.The rate of GMSL budget from 2005 to 2015 is 3.25±0.19 mm/yr close to the altimetry observations,and is equivalent to the mass + steric estimate.4.Analysis on the cause of accelerated rise of GMSL since 2011According to the characteristics of sea-level changes,we divide the sea-level changes from 2005 into six phases.We found that land water has been the dominant factor affecting sea-level changes since 2011,and the impact of land water on sea-level changes in 2005-2010 is negligible.The impact of human activities in the change of land water is further separated,the human-driven sea level change has been reduced from 2011 to 2015 by the analysis of 32 major aquifers in the world.Further analyze the impact of natural-driven,we found that the natural-driving land water slowed the rise in sea level during 2005-2010,while in 2011-2015 to promote the rise of sea level,which is closely related to global frequent extreme weather events in recent years The short-term climate factor is the main driver of the accelerated rise in sea level in recent years.