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Vendredi 20 Décembre - Present - day and projected future trends for ice sheet contributions to sea level

by SEMSOU last modified Dec 03, 2019 12:46 PM
When Dec 20, 2019
from 11:00 AM to 12:00 PM
Where salle Coriolis
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Jonathan Bamber

Bristol University, UK


Title: Present-day and projected future trends for ice sheet contributions to sea level


Abstract: Despite considerable advances in process understanding, numerical modeling and the quality of the observational record of ice sheet contributions to sea level rise (SLR) since the last IPCC report (AR5), severe limitations remain in the predictive capability of numerical modeling approaches. In this context, the potential contribution of the ice sheets remains the largest uncertainty in projecting future SLR beyond mid-century. Various approaches, including Monte Carlo ensemble emulator simulations, probabilistic or plausibility methods, and Semi Empirical Models have been used in attempts to address these limitations. To explore and quantify the uncertainties in ice sheet projections since the AR5, a Structured Expert Judgement (SEJ) exercise - involving 23 experts from North America and Europe - was undertaken in 2018.

The results of the SEJ indicated that estimates, particularly for probabilities beyond the likely range used in the AR5 (the 17th-83rd percentile), have grown since the AR5. The results indicated a 5% probability that global mean sea level could exceed 2 m by 2100, for a business-as-usual temperature scenario, with the ice sheets contributing 178 cm. The study elicited contributions for three processes - ice dynamics, accumulation and runoff-for each of the three ice sheets covering Greenland, West and East Antarctica. Here, we investigate the origins of the increased estimates relative to earlier studies and, in particular, the physical processes causing the long upper tails in the probability density functions for each ice sheet and their integrated response. To interpret the findings, we draw on process-based rationales, provided by the experts, which relate ice sheet SLR contributions to ocean and atmospheric forcing and to internal instabilities. Finally, we link the elicited ice sheet contributions to regional SLR response patterns, and we place these results in the context of the most recent SLR projections from other approaches.

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Mardi 19 Novembre - The Emerging Potential of Earth Observation for Coastal Waters

by SEMSOU last modified Nov 04, 2019 09:50 PM
When Nov 19, 2019
from 09:10 PM to 09:10 PM
Where salle Coriolis
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Arjen Luijendijk

Deltares, Delft, Netherlands


Title: The Emerging Potential of Earth Observation for Coastal Waters

Abstract: The availability of public satellite imagery, combined with advanced image interrogation and cloud computing, triggered an unprecedented flow of information relevant to the coastal engineering and research community. From satellite imagery we can nowadays for example derive subtidal bathymetry, beach slopes, beach sediment types and coastline dynamics, at accuracies that increasingly allow for engineering applications. The high spatial and temporal resolution of this information yields more comprehensive understanding of our coasts and its dynamics. This is not only of great added value in data-poor environments, it will also allow for more cost-effective coastal monitoring in data rich environments as the necessity of in-situ measurements will reduce in future. The talk will discuss the different methods and cases, with the aim to increase the level of understanding of the behavior of the world’s beaches to better support assessments on the effects of climate change.

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Jeudi 14 Novembre - Deep-ocean internal tides: observations, theory and towards a parametrisation of mixing

by SEMSOU last modified Oct 11, 2019 05:49 PM
When Nov 14, 2019
from 02:00 PM to 03:00 PM
Where salle Lyot
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Clément Vic

Laboratoire d'Océanographie Physique et Spatiale (LOPS), Brest


Title : Deep-ocean internal tides: observations, theory and towards a parametrisation of mixing


Abstract : Turbulent mixing in the ocean is key to regulate the transport of heat, freshwater and biogeochemical tracers, with strong implications for Earth’s climate. In the deep ocean, tides supply much of the mechanical energy required to sustain mixing via the generation of internal waves at tidal frequencies, called internal tides, whose fate — the relative importance of their local versus remote breaking — remains uncertain. In this presentation, I will start by reviewing our current knowledge of tidal energetics in the deep ocean, i.e., excluding continental shelves. Then, I will present some observationally-based evidence for the generation of high-mode, i.e., small-scale, internal tides over mid-ocean ridges, supported by revisited theories of tidal energy conversion. Impacts for local mixing will be discussed. Finally, I will open up towards some work in progress, seeking to build an energetically-consistent parametrisation of tidally-driven mixing.

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