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6. Impact of climate change on persistent cold-air pools in an alpine valley during the 21st century

Author

Bacer, Sara, Beaumet, Julien, Ménégoz, Martin, Gallée, Hubert, Bouëdec, Enzo, and Staquet, Chantal

Abstract

When anticyclonic conditions persist over mountainous regions in winter, cold-air pools (i.e. thermal inversion layers) develop in valleys and persist from a few days to a few weeks. During these persistent cold-air pool episodes (PCAPs) the atmosphere inside the valley is stable and vertical mixing is prevented, promoting the accumulation of pollutants close to the valley bottom and worsening air quality. It has been shown from reanalysis that the Greater Alpine Region has warmed by three degrees over the last four decades. The purpose of this paper is to address the impact of climate change on PCAPs until the end of this century for the alpine Grenoble valleys. The long-term projections produced with the general circulation model MPI downscaled over the Alps with the regional climate model MAR (Modèle Atmosphérique Régional) are used to perform a statistical study of PCAPs over the 21st century. The trends of the main characteristics of PCAPs, namely their duration, frequency, and intensity, are investigated for two future scenarios, SSP2-4.5 and SSP5-8.5. We find that the intensity of PCAPs over the 21st century displays a statistically significant decreasing trend for the SSP5-8.5 scenario only, with a very weak decay rate of 0.058 K km−1 decade−1. The impact of climate change on the detailed structure of PCAPs is next investigated by comparing two such episodes, in the past and around 2050 considering the worst-case scenario (SSP5-8.5). For this purpose, the WRF (Weather Research and Forecasting) model, forced by MAR, is used at a high resolution (111 m). The episodes are carefully selected so that a meaningful comparison can be performed. We find that these episodes present similar atmospheric circulation and heat deficit across the valley depth but different atmospheric stability and (therefore) a different inversion height. The future episode is characterised by stronger atmospheric stability and a lower inversion height and about 4 degrees warmer air both close to the surface and in altitude. Overall, this study shows that the atmosphere in the Grenoble valleys tends to be slightly less stable in the future, under the SSP5-8.5 scenario, but that intense PCAPs can still form.

Published
2023

7. Mass balance of the Greenland and Antarctic ice sheets from 1992 to 2020

Author

Otosaka, Inès N., Shepherd, Andrew, Ivins, Erik R., Schlegel, Nicole Jeanne, Amory, Charles, Van Den Broeke, Michiel R., Horwath, Martin, Joughin, Ian, King, Michalea D., Krinner, Gerhard, Nowicki, Sophie, Payne, Anthony J., Rignot, Eric, Scambos, Ted, Simon, Karen M., Smith, Benjamin E., Sørensen, Louise S., Velicogna, Isabella, Whitehouse, Pippa L., Geruo, A., Agosta, Cécile, Ahlstrøm, Andreas P., Blazquez, Alejandro, Colgan, William, Engdahl, Marcus E., Fettweis, Xavier, Forsberg, Rene, Gallée, Hubert, Gardner, Alex, Gilbert, Lin, Gourmelen, Noel, Groh, Andreas, Gunter, Brian C., Harig, Christopher, Helm, Veit, Khan, Shfaqat Abbas, Kittel, Christoph, Konrad, Hannes, Langen, Peter L., Lecavalier, Benoit S., Liang, Chia Chun, Loomis, Bryant D., McMillan, Malcolm, Melini, Daniele, Mernild, Sebastian H., Mottram, Ruth, Mouginot, Jeremie, Nilsson, Johan, Noël, Brice, Pattle, Mark E., Peltier, William R., Pie, Nadege, Roca, Mònica, Sasgen, Ingo, Save, Himanshu V., Seo, Ki Weon, Scheuchl, Bernd, Schrama, Ernst J.O., Schröder, Ludwig, Simonsen, Sebastian B., Slater, Thomas, Spada, Giorgio, Sutterley, Tyler C., Vishwakarma, Bramha Dutt, Van Wessem, Jan Melchior, Wiese, David, Van Der Wal, Wouter, Wouters, Bert, Otosaka, Inès N., Shepherd, Andrew, Ivins, Erik R., Schlegel, Nicole Jeanne, Amory, Charles, Van Den Broeke, Michiel R., Horwath, Martin, Joughin, Ian, King, Michalea D., Krinner, Gerhard, Nowicki, Sophie, Payne, Anthony J., Rignot, Eric, Scambos, Ted, Simon, Karen M., Smith, Benjamin E., Sørensen, Louise S., Velicogna, Isabella, Whitehouse, Pippa L., Geruo, A., Agosta, Cécile, Ahlstrøm, Andreas P., Blazquez, Alejandro, Colgan, William, Engdahl, Marcus E., Fettweis, Xavier, Forsberg, Rene, Gallée, Hubert, Gardner, Alex, Gilbert, Lin, Gourmelen, Noel, Groh, Andreas, Gunter, Brian C., Harig, Christopher, Helm, Veit, Khan, Shfaqat Abbas, Kittel, Christoph, Konrad, Hannes, Langen, Peter L., Lecavalier, Benoit S., Liang, Chia Chun, Loomis, Bryant D., McMillan, Malcolm, Melini, Daniele, Mernild, Sebastian H., Mottram, Ruth, Mouginot, Jeremie, Nilsson, Johan, Noël, Brice, Pattle, Mark E., Peltier, William R., Pie, Nadege, Roca, Mònica, Sasgen, Ingo, Save, Himanshu V., Seo, Ki Weon, Scheuchl, Bernd, Schrama, Ernst J.O., Schröder, Ludwig, Simonsen, Sebastian B., Slater, Thomas, Spada, Giorgio, Sutterley, Tyler C., Vishwakarma, Bramha Dutt, Van Wessem, Jan Melchior, Wiese, David, Van Der Wal, Wouter, and Wouters, Bert

Abstract

Ice losses from the Greenland and Antarctic ice sheets have accelerated since the 1990s, accounting for a significant increase in the global mean sea level. Here, we present a new 29-year record of ice sheet mass balance from 1992 to 2020 from the Ice Sheet Mass Balance Inter-comparison Exercise (IMBIE). We compare and combine 50 independent estimates of ice sheet mass balance derived from satellite observations of temporal changes in ice sheet flow, in ice sheet volume, and in Earth's gravity field. Between 1992 and 2020, the ice sheets contributed 21.0±1.9g€¯mm to global mean sea level, with the rate of mass loss rising from 105g€¯Gtg€¯yr-1 between 1992 and 1996 to 372g€¯Gtg€¯yr-1 between 2016 and 2020. In Greenland, the rate of mass loss is 169±9g€¯Gtg€¯yr-1 between 1992 and 2020, but there are large inter-annual variations in mass balance, with mass loss ranging from 86g€¯Gtg€¯yr-1 in 2017 to 444g€¯Gtg€¯yr-1 in 2019 due to large variability in surface mass balance. In Antarctica, ice losses continue to be dominated by mass loss from West Antarctica (82±9g€¯Gtg€¯yr-1) and, to a lesser extent, from the Antarctic Peninsula (13±5g€¯Gtg€¯yr-1). East Antarctica remains close to a state of balance, with a small gain of 3±15g€¯Gtg€¯yr-1, but is the most uncertain component of Antarctica's mass balance. The dataset is publicly available at 10.5285/77B64C55-7166-4A06-9DEF-2E400398E452 (IMBIE Team, 2021).

Published
2023

8. Mass balance of the Greenland and Antarctic ice sheets from 1992 to 2020

Author

Sub Dynamics Meteorology, Structural geology and EM, Marine and Atmospheric Research, Otosaka, Inès N., Shepherd, Andrew, Ivins, Erik R., Schlegel, Nicole Jeanne, Amory, Charles, Van Den Broeke, Michiel R., Horwath, Martin, Joughin, Ian, King, Michalea D., Krinner, Gerhard, Nowicki, Sophie, Payne, Anthony J., Rignot, Eric, Scambos, Ted, Simon, Karen M., Smith, Benjamin E., Sørensen, Louise S., Velicogna, Isabella, Whitehouse, Pippa L., Geruo, A., Agosta, Cécile, Ahlstrøm, Andreas P., Blazquez, Alejandro, Colgan, William, Engdahl, Marcus E., Fettweis, Xavier, Forsberg, Rene, Gallée, Hubert, Gardner, Alex, Gilbert, Lin, Gourmelen, Noel, Groh, Andreas, Gunter, Brian C., Harig, Christopher, Helm, Veit, Khan, Shfaqat Abbas, Kittel, Christoph, Konrad, Hannes, Langen, Peter L., Lecavalier, Benoit S., Liang, Chia Chun, Loomis, Bryant D., McMillan, Malcolm, Melini, Daniele, Mernild, Sebastian H., Mottram, Ruth, Mouginot, Jeremie, Nilsson, Johan, Noël, Brice, Pattle, Mark E., Peltier, William R., Pie, Nadege, Roca, Mònica, Sasgen, Ingo, Save, Himanshu V., Seo, Ki Weon, Scheuchl, Bernd, Schrama, Ernst J.O., Schröder, Ludwig, Simonsen, Sebastian B., Slater, Thomas, Spada, Giorgio, Sutterley, Tyler C., Vishwakarma, Bramha Dutt, Van Wessem, Jan Melchior, Wiese, David, Van Der Wal, Wouter, Wouters, Bert, Sub Dynamics Meteorology, Structural geology and EM, Marine and Atmospheric Research, Otosaka, Inès N., Shepherd, Andrew, Ivins, Erik R., Schlegel, Nicole Jeanne, Amory, Charles, Van Den Broeke, Michiel R., Horwath, Martin, Joughin, Ian, King, Michalea D., Krinner, Gerhard, Nowicki, Sophie, Payne, Anthony J., Rignot, Eric, Scambos, Ted, Simon, Karen M., Smith, Benjamin E., Sørensen, Louise S., Velicogna, Isabella, Whitehouse, Pippa L., Geruo, A., Agosta, Cécile, Ahlstrøm, Andreas P., Blazquez, Alejandro, Colgan, William, Engdahl, Marcus E., Fettweis, Xavier, Forsberg, Rene, Gallée, Hubert, Gardner, Alex, Gilbert, Lin, Gourmelen, Noel, Groh, Andreas, Gunter, Brian C., Harig, Christopher, Helm, Veit, Khan, Shfaqat Abbas, Kittel, Christoph, Konrad, Hannes, Langen, Peter L., Lecavalier, Benoit S., Liang, Chia Chun, Loomis, Bryant D., McMillan, Malcolm, Melini, Daniele, Mernild, Sebastian H., Mottram, Ruth, Mouginot, Jeremie, Nilsson, Johan, Noël, Brice, Pattle, Mark E., Peltier, William R., Pie, Nadege, Roca, Mònica, Sasgen, Ingo, Save, Himanshu V., Seo, Ki Weon, Scheuchl, Bernd, Schrama, Ernst J.O., Schröder, Ludwig, Simonsen, Sebastian B., Slater, Thomas, Spada, Giorgio, Sutterley, Tyler C., Vishwakarma, Bramha Dutt, Van Wessem, Jan Melchior, Wiese, David, Van Der Wal, Wouter, and Wouters, Bert

Published
2023

9. Impact of climate change on persistent cold-air pools in an alpine valley during the 21st century.

Author

Bacer, Sara, Beaumet, Julien, Ménégoz, Martin, Gallée, Hubert, Le Bouëdec, Enzo, and Staquet, Chantal

Subjects
CLIMATE change, CYCLONES, AIR pollution, POLLUTANTS, HUMIDITY
Abstract

When anticyclonic conditions persist over mountainous regions in winter, cold-air pools (i.e. thermal inversions) develop in valleys and persist from a few days to a few weeks. During these persistent cold-air pool (PCAP) episodes the atmosphere inside the valley is stable and vertical mixing is prevented, promoting the accumulation of pollutants close to the valley bottom and worsening air quality. The purpose of this paper is to address the impact of climate change on PCAPs until the end of this century for the alpine Grenoble valleys. The long-term projections produced with the general circulation model MPI (from the Max Planck Institute) downscaled over the Alps with the regional climate model MAR (Modèle Atmosphérique Régional) are used to perform a statistical study of PCAPs over the period 1981–2100. The trends of the main characteristics of PCAPs, namely their intensity, duration, and frequency, are investigated for two future scenarios, SSP2–4.5 and SSP5–8.5. We find that the intensity of PCAPs displays a statistically significant decreasing trend for the SSP5–8.5 scenario only. This decay is explained by the fact that air temperature over the century increases more at 2 m above the valley bottom than in the free air at mid-altitudes in the valley; this might be due to the increase of specific humidity near the ground. The vertical structure of two PCAPs, one in the past and one around 2050, is next investigated in detail. For this purpose, the WRF (Weather Research and Forecasting) model, forced by MAR for the worst-case scenario (SSP5–8.5), is used at a high resolution (111 m). The PCAP episodes are carefully selected from the MAR data so that a meaningful comparison can be performed. The future episode is warmer at all altitudes than the past episode (by at least 4 ∘ C) and displays a similar inversion height, which are very likely generic features of future PCAPs. The selected episodes also have similar along-valley wind but different stability, with the future episode being more stable than the past episode. Overall, this study shows that the atmosphere in the Grenoble valleys during PCAP episodes tends to be slightly less stable in the future under the SSP5–8.5 scenario, and statistically unchanged under the SSP2–4.5 scenario, but that very stable PCAPs can still form. [ABSTRACT FROM AUTHOR]

Published
2024
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10. Mass balance of the Greenland and Antarctic ice sheets from 1992 to 2020

Author

Otosaka, Inès N., primary, Shepherd, Andrew, additional, Ivins, Erik R., additional, Schlegel, Nicole-Jeanne, additional, Amory, Charles, additional, van den Broeke, Michiel R., additional, Horwath, Martin, additional, Joughin, Ian, additional, King, Michalea D., additional, Krinner, Gerhard, additional, Nowicki, Sophie, additional, Payne, Anthony J., additional, Rignot, Eric, additional, Scambos, Ted, additional, Simon, Karen M., additional, Smith, Benjamin E., additional, Sørensen, Louise S., additional, Velicogna, Isabella, additional, Whitehouse, Pippa L., additional, A, Geruo, additional, Agosta, Cécile, additional, Ahlstrøm, Andreas P., additional, Blazquez, Alejandro, additional, Colgan, William, additional, Engdahl, Marcus E., additional, Fettweis, Xavier, additional, Forsberg, Rene, additional, Gallée, Hubert, additional, Gardner, Alex, additional, Gilbert, Lin, additional, Gourmelen, Noel, additional, Groh, Andreas, additional, Gunter, Brian C., additional, Harig, Christopher, additional, Helm, Veit, additional, Khan, Shfaqat Abbas, additional, Kittel, Christoph, additional, Konrad, Hannes, additional, Langen, Peter L., additional, Lecavalier, Benoit S., additional, Liang, Chia-Chun, additional, Loomis, Bryant D., additional, McMillan, Malcolm, additional, Melini, Daniele, additional, Mernild, Sebastian H., additional, Mottram, Ruth, additional, Mouginot, Jeremie, additional, Nilsson, Johan, additional, Noël, Brice, additional, Pattle, Mark E., additional, Peltier, William R., additional, Pie, Nadege, additional, Roca, Mònica, additional, Sasgen, Ingo, additional, Save, Himanshu V., additional, Seo, Ki-Weon, additional, Scheuchl, Bernd, additional, Schrama, Ernst J. O., additional, Schröder, Ludwig, additional, Simonsen, Sebastian B., additional, Slater, Thomas, additional, Spada, Giorgio, additional, Sutterley, Tyler C., additional, Vishwakarma, Bramha Dutt, additional, van Wessem, Jan Melchior, additional, Wiese, David, additional, van der Wal, Wouter, additional, and Wouters, Bert, additional

Published
2023
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15. Mass Balance of the Greenland and Antarctic Ice Sheets from 1992 to 2020

Author

Otosaka, Inès N., primary, Shepherd, Andrew, additional, Ivins, Erik R., additional, Schlegel, Nicole-Jeanne, additional, Amory, Charles, additional, van den Broeke, Michiel, additional, Horwath, Martin, additional, Joughin, Ian, additional, King, Michalea, additional, Krinner, Gerhard, additional, Nowicki, Sophie, additional, Payne, Tony, additional, Rignot, Eric, additional, Scambos, Ted, additional, Simon, Karen M., additional, Smith, Benjamin, additional, Sandberg Sørensen, Louise, additional, Velicogna, Isabella, additional, Whitehouse, Pippa, additional, A, Geruo, additional, Agosta, Cécile, additional, Ahlstrøm, Andreas P., additional, Blazquez, Alejandro, additional, Colgan, William, additional, Engdahl, Marcus, additional, Fettweis, Xavier, additional, Forsberg, Rene, additional, Gallée, Hubert, additional, Gardner, Alex, additional, Gilbert, Lin, additional, Gourmelen, Noel, additional, Groh, Andreas, additional, Gunter, Brian C., additional, Harig, Christopher, additional, Helm, Veit, additional, Khan, Shfaqat Abbas, additional, Konrad, Hannes, additional, Langen, Peter, additional, Lecavalier, Benoit, additional, Liang, Chia-Chun, additional, Loomis, Bryant, additional, McMillan, Malcolm, additional, Melini, Daniele, additional, Mernild, Sebastian H., additional, Mottram, Ruth, additional, Mouginot, Jeremie, additional, Nilsson, Johan, additional, Noël, Brice, additional, Pattle, Mark E., additional, Peltier, William R., additional, Pie, Nadege, additional, Sasgen, Ingo, additional, Save, Himanshu, additional, Seo, Ki-Weon, additional, Scheuchl, Bernd, additional, Schrama, Ernst, additional, Schröder, Ludwig, additional, Simonsen, Sebastian B., additional, Slater, Thomas, additional, Spada, Giorgio, additional, Sutterley, Tyler, additional, Vishwakarma, Bramha Dutt, additional, van Wessem, Jan Melchior, additional, Wiese, David, additional, van der Wal, Wouter, additional, and Wouters, Bert, additional

Published
2022
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18. AMMA-MODEL INTERCOMPARISON PROJECT

Author

Hourdin, Frédéric, Musat, Ionela, Guichard, Françoise, Ruti, Paolo Michele, Favot, Florence, Filiberti, Marie-Angèle, Pham, Maï, Grandpeix, Jean-Yves, Polcher, Jan, Marquet, Pascal, Boone, Aaron, Lafore, Jean-Philippe, Redelsperger, Jean-Luc, Dell’aquila, Alessandro, Doval, Teresa Losada, Traore, Abdoul Khadre, and Gallée, Hubert

Published
2010

19. Clouds drive differences in future surface melt over the Antarctic ice shelves

Author

Kittel, Christoph, Amory, Charles, Hofer, Stefan, Agosta, Cécile, Jourdain, Nicolas C., Gilbert, Ella, Le Toumelin, Louis, Vignon, Étienne, Gallée, Hubert, Fettweis, Xavier, Kittel, Christoph, Amory, Charles, Hofer, Stefan, Agosta, Cécile, Jourdain, Nicolas C., Gilbert, Ella, Le Toumelin, Louis, Vignon, Étienne, Gallée, Hubert, and Fettweis, Xavier

Abstract

Recent warm atmospheric conditions have damaged the ice shelves of the Antarctic Peninsula through surface melt and hydrofracturing and could potentially initiate future collapse of other Antarctic ice shelves. However, model projections with similar greenhouse gas scenarios suggest large differences in cumulative 21st-century surface melting. So far it remains unclear whether these differences are due to variations in warming rates in individual models or whether local feedback mechanisms of the surface energy budget could also play a notable role. Here we use the polar-oriented regional climate model MAR (Modèle Atmosphérique Régional) to study the physical mechanisms that would control future surface melt over the Antarctic ice shelves in high-emission scenarios RCP8.5 and SSP5-8.5. We show that clouds enhance future surface melt by increasing the atmospheric emissivity and longwave radiation towards the surface. Furthermore, we highlight that differences in meltwater production for the same climate warming rate depend on cloud properties and particularly cloud phase. Clouds containing a larger amount of supercooled liquid water lead to stronger melt, subsequently favouring the absorption of solar radiation due to the snowmelt–albedo feedback. As liquid-containing clouds are projected to increase the melt spread associated with a given warming rate, they could be a major source of uncertainties in projections of the future Antarctic contribution to sea level rise.

Published
2022

40. Study of the variations in the Antarctic snow accumulation and its links with climate change in the Southern Hemisphere over the past centuries

Author

UCL - SST/ELI/ELIC - Earth & Climate, UCL - Faculté des Sciences, Goosse, Hugues, De Keersmaecker, Marie-Laurence, Lenaerts, Jan, Fichefet, Thierry, Gallée, Hubert, Yin, Qiuzhen, Dalaiden, Quentin, UCL - SST/ELI/ELIC - Earth & Climate, UCL - Faculté des Sciences, Goosse, Hugues, De Keersmaecker, Marie-Laurence, Lenaerts, Jan, Fichefet, Thierry, Gallée, Hubert, Yin, Qiuzhen, and Dalaiden, Quentin

Abstract

The Antarctic Ice Sheet (AIS) is the biggest reservoir of fresh water on Earth. During the 20th century, the AIS has gained mass at its surface through an enhanced snow accumulation. However, our understanding of the Antarctic snow accumulation variability is still limited, which directly impacts on our confidence in the future contribution of the AIS to the sea-level rise. The main objective of this thesis is to highlight the physical mechanisms behind snow accumulation variability by investigating the links between snow accumulation and other variables characterizing the surface climate at high southern latitudes. The present work is based on various types of data – instrumental observations, paleoclimate records and climate model simulations –, focuses on different time periods – from the last millennium to the 21st century – and uses diverse methodologies, such as data assimilation. Our results show that the variability in snowfall and temperature are strongly related over Antarctica, and therefore that the classical Clausius-Clapeyron relationship explains relatively well the multi-decadal, regional to continental-scale snow accumulation changes. Our work also highlights that data assimilation is particularly appropriate for reconstructing the surface climate changes in the Antarctic over the past centuries as the observational network is sparse and includes various types of records and because of the non-stationarity of the link between the proxy records and reconstructed variables. With this technique, we have been able to provide robust past estimates of temperature and snow accumulation but also of variables that cannot be directly obtained from the records themselves such as the atmospheric circulation and even the sea-ice coverage., (SC - Sciences) -- UCL, 2021

Published
2021

46. Contrasting seasonal changes in temperature, precipitation and snow cover simulated over the European Alps during the twentieth century

Author

Ménégoz, Martin, primary, Beaumet, Julien, additional, Gallée, Hubert, additional, Fettweis, Xavier, additional, Morin, Samuel, additional, Blanchet, Juliette, additional, Six, Delphine, additional, Vincent, Christian, additional, Jourdain, Nicolas C., additional, Wilhelm, Bruno, additional, and Anquetin, Sandrine, additional

Published
2021
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