Anais Orsi

Assistant Professor

Accepting students

I am a polar climate scientist, combining fieldwork in key locations, innovation in the lab, and interactions with the modelling community to better quantify our understanding of polar climate variability at the decadal to millennial scale, and to better assess the risks associated with the current global warming.

Polar regions are a key component of the Earth’s climate system, and are changing dramatically under anthropogenic climate change. The single greatest challenge for polar climate science is that there are not enough data to describe the climatology and trends. For example, in Greenland and Antarctica, historical weather stations were mostly situated on the coast; in Greenland, there were no inland stations at all before 1995. Satellite data help, but aside from their short record, they have their own limitations, like the presence of cold biases due to difficulties in separating the snow surface from low clouds. To be useful, satellite data also need ground validation. As a result, even though Greenland and Antarctica are perhaps the most sensitive regions on Earth to climate change, it is still very difficult to precisely answer questions like “How much have they been warming over the past 50 years?”, and even more difficult to put recent observations in the context of natural climate variability.

I am addressing these issues by producing new records in key locations using paleoclimate tools. The originality of my work is to use a wide variety of temperature proxies in ice cores (inert gas isotopes, water isotopes, melt layers, firn thickness, borehole temperature), analyse them with proxy system models (gas and temperature diffusion, firn densification) into a single inverse problem to produce a well constrained temperature history. I then use atmospheric reanalyses and climate model outputs to investigate the mechanisms that can be responsible for the observed variability and change.

As an example, at NEEM in North West Greenland, I used borehole temperature data, inert gas isotopes (d15N, d40Ar), and water isotope data to constrain the recent warming trend and quantify how exceptional it was in the context of the past 200 years of climate history. I demonstrated that the intense warming trend is not limited to coastal regions where melt is observed, but widespread on the ice sheet, implying that large scale dynamics are important.  I then used the MAR regional model to show that longwave feedbacks associated with an increase in atmospheric humidity are the dominant cause of surface warming on the Greenland ice sheet.

To expand the use of this type of datasets, I have worked to compile results from borehole temperature in Antarctica into easily useable metrics that can improve climate model evaluation in this data-limited region. To give a broader context to modern observations, I have produced new temperature reconstructions, and shown, for instance, that the strong warming observed in West Antarctica is within the range of natural variability at the centennial scale, and likely attributable to natural modes of variability in the Pacific Ocean, rather than a response to the anthropogenic forcing. I also work to bring many datasets together to get a broader view of regional climate variability, and I am the Antarctic ice core representative of large database efforts (PAGES temperature-2k, iso-2k, temperature-12k).

Additionally, I keep challenging how the proxies we measure are interpreted, through detailed field-based process studies (firn air experiments, water vapour isotope monitoring), improvements of proxy system models (firn densification) and associated inverse methods, and investigating sampling biases using atmospheric reanalyses and isotope-enabled global climate models. For example, Servettaz et al. (2020) clearly demonstrated that the variability in the water isotopes of East Antarctic ice cores is attributable to the presence or absence of large precipitation events in winter, and we quantified precisely the biases in the representation of the mean annual climate. These types of studies are essential for improving paleoclimate reconstructions from ice core data.

In the immediate future, I will continue to work on developing and exploiting new proxies, provide reconstructions, contribute to database work, develop collaborations with the modeling community to provide benchmarks for model evaluation, and use models to investigate mechanisms of climate variability and change.

Specifically, my efforts will be centered on four projects:

  • Investigate the mechanisms driving modern changes in Arctic humidity, using new measurements of water vapour isotopic composition in the Western Canadian Arctic. The humidity increase is involved in a dominant feedback mechanism responsible for Arctic Amplification.
  • Investigate the temporal variability of Katabatic winds in Antarctica, including ice-core proxy development, and a field campaign in the high katabatic area of Adelie Land that I will lead in 2022. It has recently been shown that 17% of Antarctic snowfall is lost by re-evaporation and wind transport, and this is a crucial part of the surface mass balance and moisture budget that is understudied.
  • Expand temperature databases, and develop new metrics of Antarctic climate variability over the Holocene to improve climate reconstructions, and better understand when the Anthropogenic warming will become visible.
  • Develop a new absolute dating technique for ice cores using Argon isotopes. This is a powerful method that can date ice that is not in stratigraphic order, and is a key component to the search for the oldest ice in Antarctica. I am working to reduce the sample requirement by a factor of 5 which would make this technique useable broadly in precious deep ice core samples.


2020 - Assistant Professor, Department of Earth Ocean and Atmospheric Sciences, University of British Columbia, Vancouver, Canada
2015 - 2020 Research Scientist, Laboratoire des Sciences du Climat et de l'Environnement, CEA Saclay, Gif Sur Yvette, France
2013 - 2015 Marie Curie Post doctoral fellow, Laboratoire des Sciences du Climat et de l'Environnement, CEA Saclay, Gif Sur Yvette, France
2013 - 03 PhD in Oceanography, Scripps Institution of Oceanography, UC San Diego, La Jolla, CA, USA
2005 MEng, Ecole Polytechnique, Palaiseau, France, major in Physics and Earth and Planetary Science


Current students:

Aymeric Servettaz, PhD, 2018-2021, Université Paris Saclay, Thesis title: Recent climate variability on the flancs of the Antarctic Plateau (Principal supervisor)
Ilaria Crotti, PhD, 2018 - 2021, University Ca'Foscari Venice, Thesis title: Dating and investigating climate variability at high resolution in the
deep portion of the Taldice ice core.
(Co supervision with B. Stenni and A. Landais)

Past students:

Camille Bréant, PhD, 2014 - 2017, Université Paris Saclay, Thesis title: Regional variability of polar densification during climate transitions. (Co supervision with P. Martinerie and A. Landais)
Clémence Brochet, M2, 2020, Université Grenoble Alpes, Thesis title: New dating of ice cores in Adélie Land, Antarctica
Léonard Barthélémy, M1, 2019, Université Grenoble Alpes, Thesis title: Climate variability of Southern Hemisphere mid and high latitudes :
contribution of the water isotope proxies.

Alassane Sane, M1, 2016, Université Paris Saclay, Thesis title: Analysis of the isotopic composition of gases trapped in firn air at
ABN, Antarctica


41. *Leroy‐Dos Santos, C., Masson‐Delmotte, V., Casado, M., Fourré, E., Steen‐Larsen, H.C., Maturilli, M., Orsi, A., Berchet, A., Cattani, O., Minster, B. and Gherardi, J., (2020) A 4.5 year‐long record of Svalbard water vapor isotopic composition documents winter air mass origin. Journal of Geophysical Research: Atmospheres, p.e2020JD032681.

40. Oyabu, I., Kawamura, K., Kitamura, K., Dallmayr, R., Kitamura, A., Sawada, C., Severinghaus, J. P., Beaudette, R., Orsi, A., Sugawara, S., Ishidoya, S., Dahl-Jensen, D., Goto-Azuma, K., Aoki, S., and Nakazawa, T.: New technique for high-precision, simultaneous measurements of CH4, N2O and CO2 concentrations, isotopic and elemental ratios of N2, O2 and Ar, and total air content in ice cores by wet extraction, Atmos. Meas. Tech. Discuss.,, accepted, 2020.

39. *Servettaz, A. P. M., Orsi, A. J., Curran, M. A. J., Moy, A. D., Landais, A., & Agosta, C., et al. (2020). Snowfall and water stable isotope variability in East Antarctica controlled by warm synoptic events. Journal of Geophysical Research: Atmospheres, 125, e2020JD032863.

38. *Lyu, Z., Orsi, A. J., & Goosse, H. (2020). Comparison of observed borehole temperatures in Antarctica with simulations using a forward model driven by climate model outputs covering the past millennium. Climate of the Past, 16(4), 1411-1428.

37. Konecky, Bronwen L., et al. incl A. Orsi. (2020). The Iso2k Database: A global compilation of paleo-δ18O and δ2H records to aid understanding of Common Era climate. Open Access Earth System Science Data .

36. Kaufman, D. et al. incl A. Orsi. (2020). A global database of Holocene paleotemperature records. Scientific Data, 7(1), 1-34.


35. Yeung, L. Y., Lee T. Murray, P. Martinerie, E. Witrant, H. Hu, A. Banerjee, A. Orsi, and J. Chappellaz. Isotopic constraint on the twentieth-century increase in tropospheric ozone. Nature 570, no. 7760, p. 224, 2019.

34. Klein, F., Abram, N. J., Curran, M. A. J., Goosse, H., Goursaud, S., Masson-Delmotte, V., Moy, A., Neukom, R., Orsi, A., Sjolte, J., Steiger, N., Stenni, B., and Werner, M.: Assessing the robustness of Antarctic temperature reconstructions over the past 2 millennia using pseudoproxy and data assimilation experiments, Clim. Past, 15, 661-684,, 2019.

33. *Bréant, C., Landais, A., Orsi, A., Martinerie, P., Extier, T., Prié, F., Stenni B., Jouzel J., Masson-Delmotte V. and Leuenberger, M. (2019). Unveiling the anatomy of Termination 3 using water and air isotopes in the Dome C ice core, East Antarctica. Quaternary Science Reviews, 211, 156-165.

32. *Bréant, C., Dos Santos, C. L., Agosta, C., Casado, M., Fourré, E., Goursaud, S., Orsi A. and Landais A.. (2019). Coastal water vapor isotopic composition driven by katabatic wind variability in summer at Dumont d'Urville, coastal East Antarctica. Earth and Planetary Science Letters, 514, 37-47.

31. Agosta, C., Amory, C., Kittel, C., Orsi, A., Favier, V., Gallée, H., & Fettweis, X. (2019). Estimation of the Antarctic surface mass balance using the regional climate model MAR (1979–2015) and identification of dominant processes. The Cryosphere, 13(1), 281-296.


30. *Yang, J. W., Han, Y., Orsi, A. J., Kim, S. J., Han, H., Ryu, Y., ... & Ahn, J. (2018). Surface temperature in twentieth century at the Styx Glacier, northern Victoria Land, Antarctica, from borehole thermometry. Geophysical Research Letters, 45(18), 9834-9842.

29. *Goursaud, S., Masson-Delmotte, V., Favier, V., Orsi, A., and Werner, M. (2018): Water stable isotope spatio-temporal variability in Antarctica in 1960–2013: observations and simulations from the ECHAM5-wiso atmospheric general circulation model, Clim. Past, 14, 923-946,

28. Bertler, N. A. N., et al., incl. A. Orsi. (2018): The Ross Sea Dipole – temperature, snow accumulation and sea ice variability in the Ross Sea region, Antarctica, over the past 2700 years, Clim. Past, 14, 193-214,, 2018.

27. Fegyveresi, J. M., Alley, R. B., Muto, A., Orsi, A. J., & Spencer, M. K. (2018). Surface formation, preservation, and history of low-porosity crusts at the WAIS Divide site, West Antarctica. Cryosphere, 12(1).


26. Stenni, B., Curran, M. A. J., Abram, N. J., Orsi, A., Goursaud, S., Masson-Delmotte, V., Neukom, R., Goosse, H., Divine, D., van Ommen, T., Steig, E. J., Dixon, D. A., Thomas, E. R., Bertler, N. A. N., Isaksson, E., Ekaykin, A., Werner, M., and Frezzotti, M. (2017), Antarctic climate variability on regional and continental scales over the last 2000 years, Clim. Past, 13, 1609-1634,, 2017

25. Carlsen, T., Birnbaum, G., Ehrlich, A., Freitag, J., Heygster, G., Istomina, L., Kipfstuhl, S., Orsi, A., Schäfer, M., and Wendisch, M. (2017),  Comparison of different methods to retrieve optical-equivalent snow grain size in central Antarctica, The Cryosphere, 11, 2727-2741,, 2017

24. Petrenko V.V., A.M. Smith, H. Schaefer, K. Riedel, E. Brook, D. Baggenstos, C. Harth, Q. Hua, C.Buizert, A. Schilt, X. Fain, L.Mitchell, T. Bauska, A. Orsi, R. F. Weiss and J. P. Severinghaus, Minimal geologic methane emissions during Younger Dryas – Preboreal abrupt warming event, Nature 548, no. 7668 (2017): 443-446.

23. Emile-Geay J, McKay NP, Kaufman DS, von Gunten L, et al. incl. A. Orsi. (2017), A global multiproxy database for temperature reconstructions of the Common Era. Scientific Data. 2017 May 3.

22. *Bréant, C., Martinerie, P., Orsi, A., Arnaud, L., and Landais, A. (2017), Modelling the firn thickness evolution during the last deglaciation: constrains on sensitivity to temperature and impurities, Clim. Past, 13, 833-853,, 2017.

21. Orsi A.J, K. Kawamura, V. Masson-Delmotte, X. Fettweis, J. Box, D. Dahl-Jensen, G.D Clow, A. Landais, and J.P. Severinghaus (2017), The recent warming trend in North Greenland, Geophys. Res. Lett., 44,

20. Lundin J.M.D, C. M. Stevens, R. Arthern, C. Buizert, A. Orsi, S. R.M. Ligtenberg, S. B. Simonsen, E. Cummings, R. Essery, W. Leahy, P. Harris, M. Helsen and E. Waddington, (2017),  Firn Model Intercomparison Experiment (FirnMICE), Journal of Glaciology, 2017, 1–22.


19. Landais, A., Masson-Delmotte, V., Capron, E., Langebroek, P. M., Bakker, P., Stone, E. J., Merz, N., Raible, C. C., Fischer, H., Orsi, A., Prié, F., Vinther, B., and Dahl-Jensen, D. (2016) How warm was Greenland during the last interglacial period?, Clim. Past, 12, 1933-1948, .

18. Jones, Julie M., Sarah T. Gille, Hugues Goosse, Nerilie J. Abram, Pablo O. Canziani, Dan J. Charman, Kyle R. Clem, Anais Orsi et al. (2016) "Assessing recent trends in high-latitude Southern Hemisphere surface climate." Nature Climate Change 6, no. 10 (2016): 917-926.

17. *Ritter, François, Hans Christian Steen-Larsen, Martin Werner, Valérie Masson-Delmotte, Anais Orsi, Melanie Behrens, Gerit Birnbaum, Johannes Freitag, Camille Risi, and Sepp Kipfstuhl, (2016) Isotopic exchange on the diurnal scale between near-surface snow and lower atmospheric water vapor at Kohnen station, East Antarctica, The Cryosphere, 10, 1647-1663,, 2016.

16. Casado, M., Cauquoin, A., Landais, A., Israel, D., Orsi, A., Pangui, E., Landsberg, J., Kerstel, E., Prie, F. and Doussin,. (2016). Experimental determination and theoretical framework of kinetic fractionation at the water vapour–ice interface at low temperature. Geochimica et Cosmochimica Acta, 174, 54-69.

15. Petrenko, V.V., Severinghaus, J.P., Schaefer, H., Smith, A.M., Kuhl, T., Baggenstos, D., Hua, Q., Brook, E.J., Rose, P., Kulin, R , Bauska, T., Harth C., Buizert C., Orsi A., Emanuel G., Lee J.E., Brailsford G., Keeling R., Weiss R.F. (2016). Measurements of 14 C in ancient ice from Taylor Glacier, Antarctica constrain in situ cosmogenic 14 CH 4 and 14 CO production rates. Geochimica et Cosmochimica Acta. 177 (2016): 62-77


14. WAIS Divide Project Members (2015), Precise interhemispheric phasing of the bipolar seesaw during abrupt Dansgaard-Oeschger events, Nature, 520, 661–665 (30 April 2015)

13. Mitchell, L. E., C. Buizert, E. J. Brook, D. J. Breton, J. Fegyveresi, D. Baggenstos, A. Orsi, J. Severinghaus, R. B. Alley, M. Albert, R. H. Rhodes, J. R. McConnell, M. Sigl, O. Maselli, S. Gregory, and J. Ahn (2015), Observing and modeling the influence of layering on bubble trapping in polar firn. J. Geophys. Res. Atmos., 120, 2558–2574.

12. Orsi, A. J., K. Kawamura, J.M. Fegyveresi, M.A. Headly, R. B. Alley and J. P. Severinghaus (2015), Differentiating bubble-free layers from melt layers in ice cores using noble gases, Journal of Glaciology, 61(227), 585-594,

11. Masson-Delmotte, V., Steen-Larsen, H. C., Ortega, P., Swingedouw, D., Popp, T., Vinther, B. M., Oerter, H., Sveinbjornsdottir, A. E., Gudlaugsdottir, H., Box, J. E., Falourd, S., Fettweis, X., Gallée, H., Garnier, E., Gkinis, V., Jouzel, J., Landais, A., Minster, B., Paradis, N., Orsi, A., Risi, C., Werner, M., and White, J. W. C. (2015). Recent changes in north-west Greenland climate documented by NEEM shallow ice core data and simulations, and implications for past temperature reconstructions, The Cryosphere, 9, 1481–1504,


10. Souney, J.M., Twickler, M.S., Hargreaves, G.M., Bencivengo, B.M., Kippenhan, M.J., Johnson, J.A., Cravens, E.D., Neff, P.D., Nunn, R.M., Orsi, A.J., Popp, T.J., Rhoades, J.F., Vaughn, B.H., Voigt, D.E., Wong, G.J. and Taylor, K.C. (2014), Core handling and processing for the WAIS Divide ice-core project, Annals of Glaciology, 55(68), p. 15 – 26

9. Orsi, A. J., B. D. Cornuelle, and J. P. Severinghaus (2014), Magnitude and Temporal Evolution of Interstadial 8 Abrupt Temperature Change Inferred From inert gas isotopes in GISP2 Ice Using a New Least-Squares Inversion, EPSL, 395:81-90.


8. WAIS Divide Project Members (2013), Onset of deglacial warming in West Antarctica driven by local orbital forcing , Nature, 500, p. 440 – 444,

7. Petrenko V., et al. incl. A. Orsi (2013), High-precision 14C measurements demonstrate production of in situ cosmogenic 14CH4 and rapid loss of in situ cosmogenic 14CO in shallow Greenland firn, EPSL, 365 190-197

6. NEEM community members (2013), Eemian interglacial reconstructed from a Greenland folded ice core, Nature, 493, 489–494,

5. Steig E.J. and Orsi A.J. (2013), Climate science: The heat is on in Antarctica, Nature Geoscience, 6, 87–88,

4. Guillevic, M., Bazin, L., Landais, A., Kindler, P., Orsi, A., Masson-Delmotte, V., Blunier, T., Buchardt, S. L., Capron, E., Leuenberger, M., Martinerie, P., Prié, F., and Vinther, B. M (2013), Spatial gradients of temperature, accumulation and δ18O-ice in Greenland over a series of Dansgaard-Oeschger events, Climate of the Past 9, 1029-1051,


3. Orsi A., B. Cornuelle and J. Severinghaus (2012), Little Ice Age Cold Interval in West Antarctica: Evidence from Borehole Temperature at the West Antarctic Ice Sheet (WAIS) Divide, Geophys. Res. Let., 39, L09710.

2. Buizert, C., Martinerie, P., Petrenko, V. V., Severinghaus, J. P., Trudinger, C. M., Witrant, E., Rosen, J. L., Orsi, A. J., Rubino, M., Etheridge, D. M., Steele, L. P., Hogan, C., Laube, J. C., Sturges, W. T., Levchenko, V. A., Smith, A. M., Levin, I., Conway, T. J., Dlugokencky, E. J., Lang, P. M., Kawamura, K., Jenk, T. M., White, J. W. C., Sowers, T., Schwander, J., and Blunier, T. (2012), Gas transport in firn: multiple-tracer characterisation and model inter-comparison for NEEM, Northern Greenland, Atmospheric Chemistry and Physics, 12, 4259-4277,


1. Battle, M. O., Severinghaus, J. P., Sofen, E. D., Plotkin, D., Orsi, A. J., Aydin, M., Montzka, S. A., Sowers, T., and Tans, P. P (2011), Controls on the movement and composition of firn air at the West Antarctic Ice Sheet Divide, Atmospheric Chemistry and Physics, 11(21), 11007-11021.