Lake and river ice cover (CLIM 020) - Assessment published Nov 2012

Key policy question: What is the trend in the ice cover of rivers and lakes across Europe?

Observed change in duration of lake and river ice cover

Note: Ice break-up dates and freezing dates of a) Danube River, at Budapest, 1876–2011 (5-year running average) and b) Lake Kallavesi, Finland, 1833–2011.

Data source:

• River Danube water temperature measurements provided by University of Natural Resources and Life Sciences, Vienna (BOKU)

• Water temperature in Lake Võrtsjärv provided by Estonian University of Life Sciences

• Hydrology and Water Resources Management Data system provided by Finnish Environment Institute (SYKE)

• First Ice Appearance and Final Disappearance on Danube River, at Budapest, 1876–2011 provided by Eötvös Loránd University, Institute of geography and earth sciences

• Temperatuur oppervlaktewater, 1910 - 2010 provided by Compendium voor de Leefomgeving

• Data on Ice-breakup Dates and Freezing Dates of Lake Kallavesi, Finland, 1833-2011 provided by Finnish Environment Institute (SYKE)

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Key assessment

Past trends

The duration of ice cover in the northern hemisphere has shortened at a mean rate of 12 days per century over the last 150–200 years, resulting from a 5.8 day later ice cover and a 6.5 day earlier ice break-up on average [i].

There are, however, large differences across regions. At the Hungarian section of the River Danube, the date of first ice appearance has shifted 19–29 days later over the 1876–2011 period, while the date of final ice disappearance shifted 18–23 days earlier [ii] (see Figure 1.a). In Lake Kallavesi, eastern Finland the freezing date has shifted 15 days later in 1833–2011, while the breakup date has shifted 12 days earlier in 1822–2011 [iii] (see Figure 1.b).

Projections

One recent study has simulated changes in lake ice cover throughout the Northern Hemisphere (40– 75 °N) based on one global climate model driven by the SRES A2 emission scenario. The results indicate an overall decrease in the duration of lake ice cover of 15–50 days across regions by 2040–2079, compared to the baseline period 1960–1999 [iv]. The ice cover of lakes in regions where the ice season is already short or where ice cover only occurs in cold winters is generally more strongly affected by increasing temperature than that of lakes in colder regions [v]. However, the ecological consequences of reduced ice cover are expected to be lower in areas where ice cover normally is less frequent and ecosystems thereby are adapted to less ice or ice-free conditions.

[i] John J. Magnuson et al., „Historical Trends in Lake and River Ice Cover in the Northern Hemisphere“, Science 289, Nr. 5485 (August 9, 2000): 1743–1746, doi:10.1126/science.289.5485.1743; EEA, Impacts of Europe’s changing climate - 2008 indicator-based assessment. Joint EEA-JRC-WHO report EEA Report (Copenhagen: European Environment Agency, September 29, 2008), http://www.eea.europa.eu/publications/eea_report_2008_4.

[ii] Katalin Takács, „Changes in river ice regime of the River Danube“ (Eötvös Loránd University, 2011), ftp://152.66.121.2/Floodrisk/_DC/docs/4_28_kkaatta.pdf.

[iii] SYKE, „Lake ice in Finland - observed trends and future outlooks.“, Finnish Environment Institute, 2011, http://www.environment.fi/default.asp?contentid=373875&lan=EN.

[iv] Y. Dibike et al., „Response of Northern Hemisphere lake-ice cover and lake-water thermal structure patterns to a changing climate“, Hydrological Processes 25 (2011): 2942–2953, doi:10.1002/hyp.8068.

[v] G. A. Weyhenmeyer et al., „Large geographical differences in the sensitivity of ice-covered lakes and rivers in the Northern Hemisphere to temperature changes“, Global Change Biology 17 (2011): 268–275, doi:10.1111/j.1365-2486.2010.02249.x.