Crustal deformation in response to climate change

The Earth’s crust deforms, mostly in the vertical direction, in response to load changes induced by the atmosphere, hydrosphere, and cryosphere, which are all affected by climate change. Largest load changes occur by deposition and melt of thick icesheets and results in tens of meters of vertical crustal movements, as recorded by uplifted shorelines in Fenoscandia and in other near polar regions. Smaller load changes induce smaller vertical crustal movements, which are measured nowadays by space geodetic techniques, mainly GPS and InSAR, with sub-cm accuracy level. Consequently, vertical crustal movements recorded by long continuous GPS time series (>15 years) provide an independent measure of climate change, which its impact can vary from one region to another. Areas subjected to rapid load changes due to icesheet melt, drought, massive groundwater extraction, or lake level drop, are characterized by rapid crustal uplift at rates of up to several cm/yr. In other areas, extraction of the climatic signal is more challenging, as seasonal load changes due to precipitation, evaporation, atmospheric load, and non-tidal ocean loading changes often mask the long-term climatic signal. However, a newly developed method that characterizes and subtracts the mean seasonal changes, provides a time series of year-to-year deviation from a mean seasonal signal, which represents long-term load changes due to climate change. The analysis of time series from the western US shows that vertical movements in the area are dominated by hydrological load changes and, consequently, the long-term climatic signal represents excess rain or drought conditions. Indeed, the GPS-derived climatic signal shows a very similar pattern to the time series of the Palmer Drought Severity Index for the same region. Vertical crustal movements in eastern North America are not correlated with hydrological load change. However, we found that the climatic signal in some stations correlates with the North Atlantic Oscillation (NAO) index, suggesting a linkage between decadal scale weather patterns in the Northern Atlantic and vertical crustal movements, possibly due to ocean and atmospheric load changes. The research results suggest that long continuous GPS observations of vertical crustal movements can serve as independent measures of regional-scale climate change.



תאריך 20/03/2016 10:30 12:00
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