• Michel, C., A. Terpstra, and T. Spengler, 2018: Polar mesoscale cyclone climatology for the Nordic seas based on ERA-Interim. J. Climate, 31, 25112532, https://doi.org/10.1175/JCLI-D-16-0890.1.

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    Cyclogenesis density of PMCs for ASIE index (a) lower than its mean minus one standard deviation and (b) greater than its mean plus one standard deviation. Unit is number of PMCs per extended winter per 104 km2. The thick black line represents 50% sea ice concentration.

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  • 1 Geophysical Institute, University of Bergen and Bjerknes Centre for Climate Research, Bergen, Norway
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© 2019 American Meteorological Society. For information regarding reuse of this content and general copyright information, consult the AMS Copyright Policy (www.ametsoc.org/PUBSReuseLicenses).

Corresponding author: Clio Michel, clio.michel@uib.no

© 2019 American Meteorological Society. For information regarding reuse of this content and general copyright information, consult the AMS Copyright Policy (www.ametsoc.org/PUBSReuseLicenses).

Corresponding author: Clio Michel, clio.michel@uib.no

In Michel et al. (2018), there was a mistake in the Arctic sea ice extent (ASIE) calculation, leading to a few deviations in section 5b, though without changing the overall results. Equation (8), Table 2, Fig. 13, and the affected parts of the text in section 5b should be as follows.

Table 2.

North Atlantic Oscillation (NAO), Scandinavian blocking (SB), and Arctic sea ice extent (ASIE) indices averaged over the genesis dates for PMCs along with their standard deviations for all polar mesoscale cyclones (ALL) and the PMCs formed in forward (FS) and reverse shear (RS) conditions. The PMCs whose genesis occurs in September are excluded from the calculation (30 PMCs for ALL, 12 for FS, 0 for RS).

Table 2.
Fig. 13.
Fig. 13.

Cyclogenesis density of PMCs for ASIE index (a) lower than its mean minus one standard deviation and (b) greater than its mean plus one standard deviation. Unit is number of PMCs per extended winter per 104 km2. The thick black line represents 50% sea ice concentration.

Citation: Journal of Climate 32, 3; 10.1175/JCLI-D-18-0759.1

The daily sea ice concentration extent A(t) is calculated as
e8

The mean value and standard deviation of the Arctic sea ice extent in the region 66°–90°N, 20°W–60°E are 1.44 ± 0.34 × 106 km2. Regressing the time series of the mean A(t) over every extended winter yields a mean sea ice extent decrease per decade during the extended winter of −0.08 × 106 km2, which is lower than the standard deviation. The cross correlations between the mean Arctic sea ice index and the number of polar mesoscale cyclones (PMCs) for each extended winter are very low with −0.16, 0.06, and −0.12 for all, forward, and reverse shear PMCs, respectively.

To assess the preference of PMC occurrence with respect to sea ice extent, we average the sea ice index over the genesis dates for all PMCs and for both genesis conditions (revised values for Table 2).

For Fig. 13, the number of PMCs fulfilling the criteria has slightly changed (1464 PMCs instead of 1490 for I ≤ −1 and 1368 PMCs instead of 1354 for I ≥ 1), but the genesis density pattern remains almost unchanged.

REFERENCE

Michel, C., A. Terpstra, and T. Spengler, 2018: Polar mesoscale cyclone climatology for the Nordic seas based on ERA-Interim. J. Climate, 31, 25112532, https://doi.org/10.1175/JCLI-D-16-0890.1.

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