The impact of the dynamic and thermodynamic flow conditions on the spatio-temporal distribution of precipitation in southern Patagonia
Atmospheric Science
Final Report Abstract
The funded research project dealt with the atmospheric flow conditions on the spatio-temporal variability of precipitation in southern Patagonia. The aim of the study was to close existing knowledge gaps in the formation of orographic precipitation and mesoscale water vapor transport along the main ridge of the Andes. To answer these questions, we applied an integrative research design combining fieldwork, state-of-the art modelling approaches, and theoretical concepts. This approach has enabled us to make significant progress in the field of the water vapor transport and the hydroclimatic response in Patagonia. So far, little was known about the hydroclimate along the main ridge of the Andes and reported projections suggested that this region is one of the wettest – if not the wettest – places on Earth. We have tested the plausability of these estimates and found new evindence that precipitation is significantly lower (~20-40%) than previously thought. This also suggest a non-negligible reduction in surface mass balance of the Patagonian Icefields. On the long-term, the regional precipitation is likely to increase by ~15% per degree warming in response to stronger moisture flux. This positive trend contradicts the recently published geodetic mass balance observations, which detected quick glacier recessions in these regions. This indicates that the evolution of the ice mass budget is partly decoupled from the climate signal and is primarily caused by dynamic adjustments of the calving glaciers in tidal and sea areas. Backward trajectories have shown that much of the available precipitable water originates from the subtropics and is efficiently transported to the poles by baroclinic eddies. The same mesoscale eddies efficiently transfer water vapor from the tropics poleward, and regularly (every 9-12 days) trigger narrow filaments of water-vapor-rich bursts called atmospheric rivers. More than half of all extreme precipitation events in Patagonia are associated with land-falling atmospheric rivers. On land-fall, the humid air masses interact with the topography and the precipitation characteristic depends on the atmospheric conditions. While under less stable conditions the Andes constitute an effective barrier to the impinging moist tropospheric air masses and force the air to ascent, strongly stable conditions can lead to blocking events. In such cases, the associated low-level barrier jet greatly reduces the uplift motions and thus the condensation of water vapor along the west slopes. The shift in the vertical uplift enhances precipitation upstream of the Andes, while reducing precipitation at the slopes. In summary, this research project has shown which processes take place between water vapour transport, topography and atmosphere and presents a significant advance in our knowledge of the hydroclimatic conditions along Patagonia’s west coast. The results of the individual subprojects might help to reduce uncertainties in the change of other precipitation-driven environmental phenomena. The work is of interest and relevance to scientists across a broad range of disciplines such as meteorology, glaciology, oceanography, biology, hydrology, and climate impact studies.
Publications
- (2016). Effects of local advection on the spatial sensible heat flux variation on a mountain glacier. The Cryosphere, 10(6), 2887–2905
Sauter, T., & Galos, S. P.
(See online at https://doi.org/10.5194/tc-10-2887-2016) - (2018). A 17-year Record of Meteorological Observations Across the Gran Campo Nevado Ice Cap in Southern Patagonia, Chile, Related to Synoptic Weather Types and Climate Modes. Frontiers in Earth Science, 6, 53
Weidemann, S. S., Sauter, T., Kilian, R., Steger, D., Butorovic, N., & Schneider, C.
(See online at https://doi.org/10.3389/feart.2018.00053) - (2018). Atmospheric controls on hydrogen and oxygen isotope composition of meteoric and surface waters in Patagonia. Hydrology and Earth System Sciences Discussions, 1–22
Mayr, C., Langhamer, L., Wissel, H., Meier, W., Sauter, T., Laprida, C., et al.
(See online at https://doi.org/10.5194/hess-2018-431) - (2018). Glacier Mass Changes of Lake-Terminating Grey and Tyndall Glaciers at the Southern Patagonia Icefield Derived from Geodetic Observations and Energy and Mass Balance Modeling. Frontiers in Earth Science, 6, 81
Weidemann, S., Sauter, T., Malz, P., Jaña, R., Arigony-Neto, J., Casassa, G., & Schneider, C.
(See online at https://doi.org/10.3389/feart.2018.00081) - (2018). Lagrangian Detection of Moisture Sources for the Southern Patagonia Icefield (1979–2017). Frontiers in Earth Science, 6, 219
Langhamer, L., Sauter, T., & Mayr, G. J.
(See online at https://doi.org/10.3389/feart.2018.00219) - (2019). Revisiting extreme precipitation amounts over southern South America and implications for the Patagonian Icefields. Hydrology and Earth System Sciences Discussions, 1–20
Sauter, T.
(See online at https://doi.org/10.5194/hess-2019-225) - (2019, February 14). Constraining glacier elevation and mass changes in South America. Nature Climate Change
Braun, M. H., Malz, P., Sommer, C., Farías-Barahona, D., Sauter, T., Casassa, G., et al.
(See online at https://doi.org/10.1038/s41558-018-0375-7)
