Future sea level rise threatens infrastructure worth trillions of euros and the livelihoods of millions of people. The magnitude and rapidity of this rise heavily relies on how the mass balance of the East Antarctic Ice Sheet (EAIS) responds to a warming climate, as a net loss of just 1% mass will increase sea level by ~0.7 m. However, any increased ice loss and resulting sea level rise may be partly offset if warming also increases snow accumulation on the EAIS. Currently, our understanding of exactly how EAIS accumulation rates respond to climate change is uncertain as modern records are sparse and the deuterium ratios used as an accumulation proxy in ice cores are affected by several other climate variables. This project aims to fully develop and apply an independent methodology to infer past snow accumulation rates using the fractionation of nitrogen isotopes in nitrate (NO3-). After NO3- is naturally deposited on the Antarctic snow surface, exposure to sunlight promotes photolytic loss of nitrate that favors 14NO3- over 15NO3-. As a result, the 15N/14N ratio (δ15N) of remaining NO3- steadily increases until enough snow accumulates to bury the NO3- below the photic zone and stop the process. Accumulation rate changes can thus extend or reduce the NO3-exposure time and degree of δ15N change. Through a suite of newly collected and archived snow/ice samples that cover a wide range of modern EAIS accumulation rates, the empirical relationship between δ15N and snow accumulation will be quantified and applied to 160 ka of data from the Vostok and EPICA Dome C ice cores. These new δ15N analyses will independently estimate how snow accumulation at the sites responded to the dramatic global climate changes of the past two glacial cycles, including two periods of rapid deglacial warming. In turn, this will produce a clearer understanding of Antarctic climate dynamics and mass balance responses during abrupt climate change and help reduce sea level projection uncertainty.
Field of science
- /natural sciences/earth and related environmental sciences/atmospheric sciences/climatology/climatic changes
Call for proposal
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