EGU2020-12957
https://doi.org/10.5194/egusphere-egu2020-12957
EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Persistent draining of the stratospheric 10Be reservoir after the Samalas volcanic eruption (1257 CE)

Mélanie Baroni1, Edouard Bard1, Jean-Robert Petit2, Sophie Viseur1, and Aster Team1,3
Mélanie Baroni et al.
  • 1Aix Marseille Univ, CNRS, IRD, INRA, Coll France, CEREGE, Aix-en-Provence, France
  • 2IGE, Univ. Grenoble Alpes, CNRS, IRD, Grenoble INP, F-38000 Grenoble, France
  • 3Georges Aumaître, Didier L. Bourlès, Karim Keddadouche

More than 2,000 analyses of beryllium‐10 (10Be) and sulphate concentrations were performed at a nominal subannual resolution on an ice core covering the last millennium as well as on shorter records from three sites in Antarctica (Dome C, South Pole, and Vostok) to better understand the increase in 10Be deposition during stratospheric volcanic eruptions.

A significant increase in 10Be concentration is observed in 14 of the 26 volcanic events studied. The slope and intercept of the linear regression between 10Be and sulphate concentrations provide different and complementary information. Slope is an indicator of the efficiency of the draining of 10Be atoms by volcanic aerosols depending on the amount of sulphur dioxide (SO2) released and on the altitude it reaches in the stratosphere. The intercept provides an appreciation of the 10Be production in the stratospheric reservoir, ultimately depending on solar modulation (Baroni et al., 2019, JGR).

Among all the identified events, the Samalas event (1257 CE) stands out as the biggest eruption of the last millennium with the lowest positive slope. It released (158 ± 12) Tg of SO2 up to an altitude of 43 km in the stratosphere (Lavigne et al., 2013, PNAS ; Vidal et al., 2016, Sci. Rep.). We hypothesize that the persistence of volcanic aerosols in the stratosphere after the Samalas eruption has drained the stratospheric 10Be reservoir for a decade.

The persistence of Samalas sulphate aerosols might be due to the increase of SO2 lifetime because of: (i) the exhaustion of the OH reservoir required for sulphate formation (e.g. (Bekki, 1995, GRL; Bekki et al., 1996, GRL; Savarino et al., 2003, JGR); and/or, (ii) the evaporation followed by photolysis of gaseous sulphuric acid back to SO2 at altitudes higher than 30 km (Delaygue et al., 2015, Tellus; Rinsland et al., 1995, GRL). In addition, the lifetime of air masses increases to 5 years above 30 km altitude compared with 1 year for aerosols and air masses in the lower stratosphere (Delaygue et al., 2015, Tellus). When this high-altitude SO2 finally returns below the 30 km limit, it could be oxidized back to sulphate and forms new sulphate aerosols. These processes could imply that the 10Be reservoir is washed out over a long time period following the end of the eruption of Samalas.

This would run counter to modelling studies that predict the formation of large particle sizes and their rapid fall out due to the large amount of SO2, which would limit the climatic impact of Samalas-type eruptions (Pinto et al., 1989, JGR; Timmreck et al., 2010, 2009, GRL).

How to cite: Baroni, M., Bard, E., Petit, J.-R., Viseur, S., and Team, A.: Persistent draining of the stratospheric 10Be reservoir after the Samalas volcanic eruption (1257 CE), EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-12957, https://doi.org/10.5194/egusphere-egu2020-12957, 2020

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Presentation version 1 – uploaded on 04 May 2020
  • CC1: Comment on EGU2020-12957, Myriam Khodri, 05 May 2020

    Dear Melanie et al,

    Interesting work!  The negative slopes for eruptions following the Samalas eruption (in 1269CE and 1276CE) would reflect a 10Be washout for at least a decade. Do you have an explanation? Would that mean that after Salamas it takes about a decade to restor 10Be stratospheric reservoir? Or that oxidation of SO2 from Salamas eruption would last a decade ?

    Best regards,

    Myriam 

    • AC1: Reply to CC1, Mélanie Baroni, 05 May 2020

      Dear Myriam,

      Thank you for your interesting question ! The answer is probably both. We think that the negative slopes of the eruptions following the Samalas one, would indicate that the 10Be polar stratospheric reservoir was not anymore in a steady-state because of a persistent draining caused by sulphate aerosols and the persistence of sulphate aerosols after the Samalas eruption could be due to the oxidation of SO2 that would have been possible for a decade. The large amount of SO2 emitted (158Tg-Lavigne et al., 2013) could have exhausted the OH reservoir responsible for the oxidation to sulfate, which could have increased the SO2 lifetime (e.g. Bekki et al., 1995,1996; Savarino et al., 2003)) and the altitude at which it has been injected (43km-Lavigne et al., 2013) may have also played a role because above 30km of altitude, the age of air masses can reach 5 years and gaseous sulphuric acid can be evaporated and photolyzed back to SO2 (e.g. Delaygue et al., 2015; Rinsland et al., 1995). When this SO2 would finally return below 30km of altitude, it could be oxidized to sulphate. Models would help a lot to test these hypotheses !