Person: Blasco Navarro, Javier
Universidad Complutense de Madrid
Faculty / Institute
Física de la Tierra y Astrofísica
Now showing 1 - 2 of 2
- PublicationExploring the impact of atmospheric forcing and basal drag on the Antarctic Ice Sheet under Last Glacial Maximum conditions(Copernicus Gesellschaft MBH, 2021-01-18) Blasco Navarro, Javier; Álvarez Solas, Jorge; Robinson, Alexander James; Montoya Redondo, María LuisaLittle is known about the distribution of ice in the Antarctic Ice Sheet (AIS) during the Last Glacial Maximum (LGM). Whereas marine and terrestrial geological data indicate that the grounded ice advanced to a position close to the continental-shelf break, the total ice volume is unclear. Glacial boundary conditions are potentially important sources of uncertainty, in particular basal friction and climatic boundary conditions. Basal friction exerts a strong control on the large-scale dynamics of the ice sheet and thus affects its size and is not well constrained. Glacial climatic boundary conditions determine the net accumulation and ice temperature and are also poorly known. Here we explore the effect of the uncertainty in both features on the total simulated ice storage of the AIS at the LGM. For this purpose we use a hybrid ice sheet shelf model that is forced with different basal drag choices and glacial background climatic conditions obtained from the LGM ensemble climate simulations of the third phase of the Paleoclimate Modelling Intercomparison Project (PMIP3). Overall, we find that the spread in the simulated ice volume for the tested basal drag parameterizations is about the same range as for the different general circulation model (GCM) forcings (4 to 6 m sea level equivalent). For a wide range of plausible basal friction configurations, the simulated ice dynamics vary widely but all simulations produce fully extended ice sheets towards the continental-shelf break. More dynamically active ice sheets correspond to lower ice volumes, while they remain consistent with the available constraints on ice extent. Thus, this work points to the possibility of an AIS with very active ice streams during the LGM. In addition, we find that the surface boundary temperature field plays a crucial role in determining the ice extent through its effect on viscosity. For ice sheets of a similar extent and comparable dynamics, we find that the precipitation field determines the total AIS volume. However, precipitation is highly uncertain. Climatic fields simulated by climate models show more precipitation in coastal regions than a spatially uniform anomaly, which can lead to larger ice volumes. Our results strongly support using these paleoclimatic fields to simulate and study the LGM and potentially other time periods like the last interglacial. However, their accuracy must be assessed as well, as differences between climate model forcing lead to a large spread in the simulated ice volume and extensión.
- PublicationAssessing the Antarctic sea-level contribution from the Last Glacial Period to the future(Universidad Complutense de Madrid, 2021-06-30) Blasco Navarro, Javier; Robinson, Alexander; Álvarez Solas, JorgeSea-level rise is one of the biggest threats to modern humankind. The AntarcticIce Sheet (AIS) plays an important role in future projection, as it is the largest ice sheet on Earth, and hence the potential major contributor. However, as putin the Intergovernmental Panel on Climate Change (IPCC) fth report, the AISis also the largest source of uncertainty to sea-level rise. Part of this uncertainty arises due to uncertain future projections. Another source relies on the underlying mechanisms that drive the evolution of large continental ice sheets. Basal frictionas well as ice-ocean interactions are probably one of the most important, and yet unknown, building blocks in de ning the evolution of the AIS. This occurs because basal and sub-shelf processes are compounded into complex systems which are highly unconstrained. Through satellite observations it is possible to infer properties of these features but it does not give information about how it evolved in the past or the future. A way to gain insight into sub-shelf melting and basal friction, as well as future projections, is through paleo-modeling studies. Paleo-modeling studies are essential tools, as they allow not only analysis of the behaviour of ice sheets under past climatologies, but also to investigate the role of dierent features, such as ice dynamics, and compare with proxy data...