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An Assessment of the Temporal Variability in the Annual Cycle of Daily Antarctic Sea Ice in the NCAR Community Earth System Model, Version 2: A Comparison of the Historical Runs With Observations

Raphael, Marilyn N. ; Handcock, Mark S. ; Holland, Marika M. ; Landrum, Laura L.

Journal of geophysical research. Oceans, 2020-11, Vol.125 (11), p.n/a [Periódico revisado por pares]

Washington: Blackwell Publishing Ltd

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  • Título:
    An Assessment of the Temporal Variability in the Annual Cycle of Daily Antarctic Sea Ice in the NCAR Community Earth System Model, Version 2: A Comparison of the Historical Runs With Observations
  • Autor: Raphael, Marilyn N. ; Handcock, Mark S. ; Holland, Marika M. ; Landrum, Laura L.
  • Assuntos: Amplitude ; Amplitudes ; Annual variations ; Antarctic circulation ; Antarctic sea ice ; Antarctic sea ice variability ; Atmospheric circulation ; Atmospheric models ; Atmospheric research ; Climate ; Climate change ; Climate models ; climate system modeling ; Daily ; daily Antarctic sea ice ; Estimates ; Future climates ; Geophysics ; H system ; observed and simulated sea ice comparisons ; Polar environments ; Satellite observation ; Satellites ; Sea ice ; sea ice atmosphere interaction ; Semiannual oscillation ; Simulation ; Statistical analysis ; statistical estimation of sea ice variability ; Storms ; Temporal variability ; Temporal variations ; Variability ; Volatility
  • É parte de: Journal of geophysical research. Oceans, 2020-11, Vol.125 (11), p.n/a
  • Descrição: Understanding the variability of Antarctic sea ice is an ongoing challenge given the limitations of observed data. Coupled climate model simulations present the opportunity to examine this variability in Antarctic sea ice. Here, the daily sea ice extent simulated by the newly released National Center for Atmospheric Research (NCAR) Community Eart h System Model Version 2 (CESM2) for the historical period (1979–2014) is compared to the satellite‐observed daily sea ice extent for the same period. The comparisons are made using a newly developed suite of statistical metrics that estimates the variability of the sea ice extent on timescales ranging from the long‐term decadal to the short term, intraday scales. Assessed are the annual cycle, trend, day‐to‐day change, and the volatility, a new statistic that estimates the variability at the daily scale. Results show that the trend in observed daily sea ice is dominated by subdecadal variability with a weak positive linear trend superimposed. The CESM2 simulates comparable subdecadal variability but with a strong negative linear trend superimposed. The CESM2's annual cycle is similar in amplitude to the observed, key differences being the timing of ice advance and retreat. The sea ice begins its advance later, reaches its maximum later and begins retreat later in the CESM2. This is confirmed by the day‐to‐day change. Apparent in all of the sea ice regions, this behavior suggests the influence of the semiannual oscillation of the circumpolar trough. The volatility, which is associated with smaller scale dynamics such as storms, is smaller in the CESM2 than observed. Plain Language Summary Antarctic sea ice is strongly variable in space and in time. Lack of observed data makes it difficult to determine what causes this variability and limits our ability to understand the variability and to project how it might change in the future. Climate models give the opportunity to study the sea ice and to project change. We compare the sea ice simulations produced by the National Center for Atmospheric Research (NCAR) Community Earth System Model Version 2 (CESM2) with satellite‐observed data for the years 1979–2014. We examine the annual cycle, trend, day‐to‐day change in sea ice and the volatility, a new statistic that estimates the variability at the daily scale. We show that the CESM2 is able to simulate subdecadal variability comparable to that apparent in the observed sea ice but not the weak, positive, linear trend. The CESM2 also simulates an annual cycle of similar amplitude to that observed but the ice starts growing later and retreating later in the CESM2 than is observed. This difference in timing in the annual cycle occurs in the sea ice all around Antarctica, which suggests that it might be because of a circum‐Antarctic atmospheric circulation feature called the circumpolar trough. Key Points Antarctic sea ice extent variability is dominated by subdecadal variability, and that is well represented in the CESM2 simulations The CESM2 simulates an annual cycle of sea ice extent that is comparable in size to that observed but begins its advance and retreat later The later retreat of the CESM2 sea ice is potentially related to its simulation of the semiannual oscillation of the circumpolar trough
  • Editor: Washington: Blackwell Publishing Ltd
  • Idioma: Inglês
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