About one year after the return of the German research icebreaker RV Polarstern, a number of studies resulting from MOSAiC, the ever biggest Arctic international expedition have already been published. Here, we briefly summarize their results.
On 12 October 2020, RV Polarstern returned to Bremerhaven from the MOSAiC (Multidisciplinary drifting Observatory for the Study of Arctic Climate) expedition, 389 days after the ship left for the Arctic in fall 2019. During its mission, Polarstern was anchored to an ice floe and drifted with the ice through the Arctic Ocean. MOSAiC aimed at gathering data from the sea ice, the atmosphere, and the ocean and their interactions with each other. The collected data should help scientists to fill the knowledge gaps on processes taking place particularly during Arctic winter from which only limited observations were yet available due to the very harsh conditions making the central Arctic inaccessible during winter.
In June this year, von der Gathen et al. published in “Nature Communications” their article “Climate change favours large seasonal loss of Arctic ozone”. By looking at the formation of polar stratospheric clouds (PSCs) in cold winters and the output from General Circulation Models (GCMs), the authors monitor the Arctic ozone loss. They conclude that the potential formation of PSCs has a positive trend from 1950 to 2100. At the end of the century, the highest values are reached in their simulations where the radiative forcing of climate is increased by greenhouse gases. The Authors suspect that favorable conditions for large, seasonal loss of Arctic ozone could continue or potentially worsen until the end of the century if the emissions of greenhouse gases continue to rise. (ph)
Another study dealing with ozone loss entitled “Near-Complete Local Reduction of Arctic Stratospheric Ozone by Severe Chemical Loss in Spring 2020“ was already released in September 2020 by Wohltmann et al. in GRL, the “Geophysical Research Letters”. The authors state that the ozone loss in the Arctic, which normally is more limited than the ozone loss in the Antarctic, had reached values of 93%, during measurements from 17 March to 17 April 2020, compared to 95-99% in the Antarctic. Additionally, the portion of ozone in the atmosphere, which never before dropped below 0.5 ppm, had reached values of 0.2 ppm with individual profiles reaching 0.13 ppm in Eureka, Canada on 24 March 2020. The reason for this reduced mixing ratio was an unusually strong, stable, and cold polar vortex which lasted until early to mid-May. (ph)
A study by Katlein et al. also in GRL from August 2020 on “Platelet Ice Under Arctic Pack Ice in Winter” is about decimeter-sized thin ice plates, so-called platelet ice, which grows on the underside of sea ice. Platelet ice is mostly found in the Antarctic where it forms from water that is below the local freezing point. However, during the MOSAiC expedition, the authors could observe the formation of platelet ice in freely drifting pack ice during the Arctic winter; they conclude that platelet ice formation is a widely spread process in the Arctic during winter. (ph)
Krumpen et al. examined the ice floe on which “Polarstern” was initially anchored in fall 2019 and where most of the MOSAiC experiments were carried out during the first legs. In their study entitled “The MOSAiC ice floe: sediment-laden survivor from the Siberian shelf” which was published in “The Cryosphere” in February 2020, the authors were able to determine that the MOSAIC ice floe, that was also called the fortress due to its initial stability, had been formed north of the New Siberian Islands in December 2018. Measurements showed that the sea ice in the vicinity of the Central Observatory was 36% thinner and younger than the surrounding ice. In September 2019, the ice was already classified as exceptionally thin compared to data from the last 26 years, which leads to a higher possibility of a seasonally ice-free Arctic Ocean with big impacts on the Central Arctic ecosystem. (ph)
In June 2021, also Belter et al. published their study on sea ice “Interannual variability in Transpolar Drift summer sea ice thickness and potential impact of Atlantification” in “The Cryosphere”. The authors compare a summer time series, taken from July to August, of extensive ice thickness surveys from the end of the Transpolar Drift between 2001 and 2020 with preliminary results from the MOSAiC expedition. The results show that modal summer ice thickness of the MOSAiC floe and its surroundings are consistent with measurements from the late Transpolar Drift. The authors conclude that the winter sea-ice growth could be limited in time in the future while effects of processes, such as the Atlantification of the Arctic Ocean, would become extended over the summer season due to the shortened duration of the Transpolar Drift in the upcoming years. (ph)
A study published December 2020 by Stroeve et al. also in “The Cryosphere” with the title “Surface-based Ku- and Ka-band polarimetric radar for sea ice studies” was carried out to better understand how snow properties influence sea-ice thickness retrievals. The authors examined the potential for combining dual frequencies to simultaneously map snow depth and sea ice thickness with the Ku- and Ka-band radar. (ph)
In their article “Snow and Ice Thickness Retrievals Using GNSS-R: Preliminary Results of the MOSAiC Experiment”, Munoz-Martin et al. present techniques needed for measuring snow and sea ice thickness and the theory behind the Global Navigation Satellite Systems reflectometry (GNSS-R). The authors showed that this system is fully usable for measurements in the Arctic. The measurements published in the journal “Remote Sensing” in December 2020 showed that the snow layer over sea ice is dominant, while the ice thickness seems to have a smaller impact on the GNSS reflections. There is some sensitivity to ice thickness variations, especially at the lower frequency band, shown by the interference pattern which was produced by the four-layer model. (ph)
A recently published article on “Meteorological conditions during the MOSAiC expedition: Normal or anomalous?” by Rinke et al. in Elementa: Science of the Anthropocene depicts the meteorological conditions during the MOSAiC expedition. Furthermore, it compares the near-surface meteorological conditions with the interannual variability and extremes within the past four decades, based on hourly ERA5 reanalysis data. The conditions experienced at the research icebreaker RV Polarstern were relatively normal. However, from time to time from late fall 2019 until early spring 2020 anomalous and record-breaking conditions were recorded such as cases of especially warm and moist air intrusions as well as strong storm events during winter and spring. The summer was all-time warmest and wettest in July and August 2020. Moreover, the near-melting point conditions lasted more than a month longer than usual. These results fit into the general trend of increasing temperature and moisture in the central Arctic. Contrary, from November 2019 to March 2020 unusually cold conditions occurred, these are associated with a positive phase of the Arctic Oscillation pattern. (th)
At least five other publications, amongst them are Krumpen et al. (preprint) and Dethloff et al. (preprint) are currently under review and will be released in the near future.
Belter, H. J., Krumpen, T., von Albedyll, L., Alekseeva, T. A., Birnbaum, G., Frolov, S. V., Hendricks, S., Herber, A., Polyakov, I., Raphael, I., Ricker, R., Serovetnikov, S. S., Webster, M., and Haas, C. (2021). Interannual variability in Transpolar Drift summer sea ice thickness and potential impact of Atlantification. The Cryosphere, 15, 2575–2591, doi.org/10.5194/tc-15-2575-2021.
von der Gathen, P., Kivi, R., Wohltmann, I. et al. (2021). Climate change favours large seasonal loss of Arctic ozone. Nature Communications 12, 3886. doi.org/10.1038/s41467-021-24089-6
Katlein, C., Mohrholz, V., Sheikin, I., Itkin, P., Divine, D. V., & Stroeve, J., et al. (2020). Platelet Ice Under Arctic Pack Ice in Winter. Geophysical Research Letters, 47, e2020GL088898. doi.org/10.1029/2020GL088898
Krumpen, T., Birrien, F., Kauker, F., Rackow, T., von Albedyll, L., Angelopoulos, M., Belter, H. J., Bessonov, V., Damm, E., Dethloff, K., Haapala, J., Haas, C., Harris, C., Hendricks, S., Hoelemann, J., Hoppmann, M., Kaleschke, L., Karcher, M., Kolabutin, N., Lei, R., Lenz, J., Morgenstern, A., Nicolaus, M., Nixdorf, U., Petrovsky, T., Rabe, B., Rabenstein, L., Rex, M., Ricker, R., Rohde, J., Shimanchuk, E., Singha, S., Smolyanitsky, V., Sokolov, V., Stanton, T., Timofeeva, A., Tsamados, M., and Watkins, D. (2020). The MOSAiC ice floe: sediment-laden survivor from the Siberian shelf. The Cryosphere, 14, 2173–2187. doi.org/10.5194/tc-14-2173-2020.
Munoz-Martin, J.F., Perez, A., Camps, A., Ribó, S., Cardellach, E., Stroeve, J., Nandan, V., Itkin, P., Tonboe, R., Hendricks, S., Huntemann, M., Spreen, G., Pastena, M. (2020). Snow and Ice Thickness Retrievals Using GNSS-R: Preliminary Results of the MOSAiC Experiment. Remote Sensing, 12, 4038. doi.org/10.3390/rs12244038.
Rinke, A., Cassano, J., Cassano, E.N., Jaiser, R., Handorf, D. (2021). Meteorological conditions during the MOSAiC expedition: Normal or anomalous? Elementa: Science of the Anthropocene, 9(1), 00023. doi.org/10.1525/elementa.2021.00023.
Stroeve, J., Nandan, V., Willatt, R., Tonboe, R., Hendricks, S., Ricker, R., Mead, J., Mallett, R., Huntemann, M., Itkin, P., Schneebeli, M., Krampe, D., Spreen, G., Wilkinson, J., Matero, I., Hoppmann, M., and Tsamados, M. (2020). Surface-based Ku- and Ka-band polarimetric radar for sea ice studies. The Cryosphere, 14, 4405–4426. doi.org/10.5194/tc-14-4405-2020.
Wohltmann, I., von der Gathen, P., Lehmann, R., Maturilli, M., Deckelmann, H., Manney, G. L., et al. (2020). Near-Complete Local Reduction of Arctic Stratospheric Ozone by Severe Chemical Loss in Spring 2020. Geophysical Research Letters, 47, e2020GL089547. doi.org/10.1029/2020GL089547.
