PAIS: The Sound of a Community Effort

“Every contribution matters.” Anybody who ever played in a sport team probably heard this sentence at some point. Actually, this is completely true also as far as science is concerned. Whereas in the collective imagination science is about big discoveries made by a single genius, the truth is that great science is made little by little, step by step. Science is a community effort in which every contribution matters. And that is the concept from which this video was born. 

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PAIS publication acknowledgement:

Where PAIS activities have contributed to thinking or ideas behind a research publication it is appropriate to acknowledge SCAR PAIS, such as  “This research is a contribution to the SCAR PAIS program”. Please notify us of the paper by emailing ldesantis@inogs.it and  timothy.naish@vuw.ac.nz

SCAR Scientific Research Programme PAIS

The SCAR Scientific Research Programme PAIS (Past Antarctic Ice Sheet dynamics) aims to improve understanding of the sensitivity of East, West, and Antarctic Peninsula Ice Sheets to a broad range of climatic and oceanic conditions.

PAIS builds on the success of SCAR-ACE (Antarctic Climate Evolution), but with a new focus on the ice sheet rather than palaeoclimate reconstructions. Study intervals span a range of timescales, including past "greenhouse" climates warmer than today, and times of more recent warming and ice sheet retreat during glacial terminations.

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A new field work study evaluates how katabatic winds can reduce the amount of precipitation actually reaching the surface.

PNAS from Grazioli et al, 2017

Accumulation of precipitation is the principal input contribution to the ice sheet mass balance in Antarctica. Yet, only very few in situ snowfall observations are realised and the only way to evaluate globally around Antarctica the evolution of the snowfall rates is through satellite observations. New weather radar measurements of precipitation realised at the coastal station Dumont d’Urville show that these satellite observations might be biased and not provide an accurate estimate of the precipitation actually reaching the surface. Indeed, due to the presence of warm, undersaturated air close to the surface (below 800m), a significant amount of the precipitation sublimates before it touches the ground (see Fig. 1a)). This feature is due to the presence of katabatic winds which are spread all around the margins of Antarctica. Yet, satellite usually cannot see close to the surface and use measurements above 800m as a proxy for surface precipitation.

Fig news grazioli

Fig 1: a) Schematic of the sublimation of precipitation near the surface due to warm undersaturated air created by katabatic wind and b) map of the amount of snowfall sublimating through this layer around Antarctica, adapted from Grazioli et al. [2017]  

Three different modelling exercises have been able to reproduce the observations of sublimation of the precipitation. They highlight that roughly 17% of the total snowfall on the entire continent never reaches the ground, and that on the East Antarctic margin it can reach up to 50% (see Fig. 1b)).

These low-level sublimations of precipitation can directly affect prediction for ice sheet mass balance in the context of climate change. Indeed, as a thermodynamical response to global warming, the snowfall increases as the atmosphere is able to hold more moisture. Yet, changes in the moisture content and in the strength of katabatic winds are also expected and low-level sublimations of precipitation associated with warmer temperature could compensate snowfall increase.

Grazioli, J. et al. Katabatic winds diminish precipitation contribution to the Antarctic ice mass balance. Proceedings of the National Academy of Sciences, 201707633

Full article at: http://www.pnas.org/content/114/41/10858.full

MC