01 Nov 2022
01 Nov 2022
Status: this preprint is open for discussion.

Estimating the uncertainty of sea-ice area and sea-ice extent from satellite retrievals

Andreas Wernecke1,2, Dirk Notz1,2, Stefan Kern2, and Thomas Lavergne3 Andreas Wernecke et al.
  • 1Max Planck Institute for Meteorology, Hamburg, Germany
  • 2Center for Earth System Research and Sustainability (CEN), Institute of Oceanography, Universität Hamburg, Hamburg, Germany
  • 3Norwegian Meteorological Institute, Oslo, Norway

Abstract. The net Arctic sea-ice area (SIA) can be estimated from the routine monitoring of sea-ice concentration (SIC) by passive microwave measurements from satellites. To be a truly useful metric, for example, of the sensitivity of the Arctic sea-ice cover to global warming, we need, however, reliable estimates of its uncertainty . We here derive this uncertainty by taking spatial and temporal error correlations of the underlying local sea ice concentration products into account. Doing so, we find that the observational uncertainties of both sea-ice area and sea-ice extent (SIE) in 2015 are about 300 000 km2 for daily and weekly estimates and 160 000 km2 for monthly estimates. This is about half of the spread in estimated sea-ice area from different passive microwave SIC products, showing that random SIC errors play at least as much a role in SIA uncertainties as inter-SIC-product biases. We further show that the trend of SIA in September, which is traditionally the month with least Arctic sea ice is 105 000 km2 a-1 ± 9 000 km2 a-1 for the period from 2002 to 2017. This is the first estimate of a SIA trend with an explicit representation of temporal error correlations.

Andreas Wernecke et al.

Status: open

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Andreas Wernecke et al.

Model code and software

Script to create MC ensemble to represent uncertainties in ESA CCI SIC dataset Andreas Wernecke

Andreas Wernecke et al.


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Short summary
The total area of Arctic sea ice (SIA) is routinely monitored with the help of satellite measurements, which is an important climate indicator. Uncertainties in observations of sea-ice concentration (SIC) cancel out when averaging but the degree to which this is happening has been unclear. We calculate the uncertainty in SIA based on uncertainties in SIC . We find that daily SIA estimates have uncertainties of about 300 000 km2; The 2002 to 2017 September trend is 105 000 ± 9 000 km2 per year.