Séminaire PMMH - Louis-Alexandre Couston (ENS Lyon)

Vendredi 17 mai de 11h00 à 12h00 - Salle réunion PMMH 1

What we know and don't know about the ocean circulation and ice melting around Antarctica

The Antarctic ice sheet is losing mass increasingly rapidly and could
contribute several tens of centimetres of sea-level rise by 2100. In
this presentation I will review our understanding of the southern ocean
circulation, which (we know) is controlling ice melting around
Antarctica and driving the retreat of the ice sheet. I will describe the
ocean dynamics at both large and small scales. Notably, I will explain
why the ocean circulation below ice shelves (floating extensions of the
ice sheet, hundreds of kilometres long) may tip from cold to warm
conditions abruptly. Then, I will review the different (turbulent)
regimes of ice-ocean boundary layers (only few meters thick), which
control heat exchanges between warm deep-water masses and the overlying
ice shelves and icebergs. Throughout the presentation I will highlight
knowledge gaps and discuss recent works from our group, including
laboratory experiments and turbulence-resolving phase change
simulations, aiming to improve our understanding and modelling
capabilities of ocean flows around Antarctica.