Lake and river ice cover
- The duration of ice cover in the northern hemisphere has shortened at a mean rate of 12 days per century, resulting from an average 5.7 days later ice cover and 6.3 days earlier ice break-up.
- The strongest trends in northern Europe are in the timing of ice break-up which is consistent with the fastest warming in winter and spring.
- The ice cover of lakes with mean winter temperature close to zero is much more dependent on temperature change than lakes in colder regions such as northern Scandinavia.
Ice break-up dates from selected European lakes and rivers (1835-2006) and the North Atlantic Oscillation (NAO) index for winter 1864-2006
Note: Time series of ice break-up dates from selected European lakes and rivers. Data smoothed with a 7-year moving average
Benson, B. and Magnuson, J., 2000 (updated 2006). Global lake and river ice phenology database. In: Boulder, C.O., National Snow and Ice Data Center/World Data Center for Glaciology.Bauernfeind, E. and U.H. Humpesch 2001. Die Eintagsfliegen Zentraleuropas (Insecta: Ephemeroptera) Bestimmung und Ökologie. Verlag des Naturhistorischen Museums, Wien Austria.
An analysis of long (more than 150 year) ice records from lakes and rivers throughout the northern hemisphere by Magnuson et al. (2000) indicated that for a 100 year period, ice cover has been occurring on average 5.7 +/- 2.4 days later (+/- 95 % confidence interval), while ice break-up has been occurring on average 6.3 +/- 1.6 days earlier, implying an overall decrease in the duration of ice cover at a mean rate of 12 days per 100 years. These results do not appear to change with latitude, or between North America and Eurasia, or between rivers and lakes.
Changes in ice parameters mostly show trends that are in agreement with observed local temperature increases. Air temperature is the key variable determining the timing of ice break-up (Palecki and Barry, 1986; Livingstone, 1997).
A few longer time-series reveal reduced ice cover (a warming trend) beginning as early as the 16th century, with increasing rates of change after about 1850 (see Figure 1). The early and long-term decreasing trend in the ice break-up dates is the result of the end of the Little Ice Age, which lasted from about 1400 to 1900 (Kerr, 1999). In the 20th century, the effects of the North Atlantic Oscillation on the ice regime of European inland waters appear to be stronger than the effects of increasing temperatures.
Studying ice cover information from 11 Swiss lakes over the last century, Franssen and Scherrer (2008) found that ice cover was significantly reduced in the past 40 years, and especially during the past two decades.
Ice cover of lakes in southern Sweden is more sensitive to climate change than those in the north, where mean winter temperatures are below zero most of the winter. A study of 196 Swedish lakes along a latitudinal temperature gradient revealed that a 1 oC air temperature increase caused an up to 35 days earlier ice break-up in Sweden's warmest southern regions with annual mean air temperatures around 7 oC. It caused only about 5 days earlier break-up in Sweden's coldest northern regions where annual mean air temperatures are around - 2 oC (Weyhenmeyer et al., 2004; Weyhenmeyer, 2007). Ice break-up in Finland has also become significantly earlier from the late 19th century to the present time, except in the very north (Korhonen, 2006).
Future increases in air temperature associated with climate change are likely to result in generally shorter periods of ice cover on lakes and rivers. The most rapid decrease in the duration of ice cover will occur in the temperate region where the ice season is already short or only occurs in cold winters (Weyhenmeyer et al., 2004). As a result, some of the lakes that now freeze in winter and that mix from top to bottom during two mixing periods each year (dimictic lakes) will potentially change into monomictic (mixing only once) open-water lakes with consequences for vertical mixing, deep-water oxygenation, nutrient recycling and algal productivity. This may lead to an alteration in the ecological status of normally ice-covered lakes in temperate regions.
Regional climate model projections for northern Germany, based on the IPCC high emissions SRES A2 and intermediate emissions B2 climate scenarios, imply that for the Muggelsee, the percentage of ice-free winters will increase from about 2 % now to more than 60 % by the end of the century (Livingstone and Adrian, submitted). In contrast, increases in mean annual air temperature are likely to have a much smaller effect on lakes in very cold regions (e.g. northern Scandinavia) until these also reach the threshold of having winter temperature close to zero.
Indicator specification and metadata
- Ice break-up dates from selected European lakes and rivers (1835-2006) and the North Atlantic Oscillation (NAO) index for winter 1864-2006
Policy context and targets
In April 2009 the European Commission presented a White Paper on the framework for adaptation policies and measures to reduce the European Union's vulnerability to the impacts of climate change. The aim is to increase the resilience to climate change of health, property and the productive functions of land, inter alia by improving the management of water resources and ecosystems. More knowledge is needed on climate impact and vulnerability but a considerable amount of information and research already exists which can be shared better through a proposed Clearing House Mechanism. The White Paper stresses the need to mainstream adaptation into existing and new EU policies. A number of Member States have already taken action and several have prepared national adaptation plans. The EU is also developing actions to enhance and finance adaptation in developing countries as part of a new post-2012 global climate agreement expected in Copenhagen (Dec. 2009). For more information see: http://ec.europa.eu/environment/climat/adaptation/index_en.htm
No targets have been specified
Related policy documents
No related policy documents have been specified
Methodology for indicator calculation
Methodology for gap filling
No methodology references available.
Data sets uncertainty
No uncertainty has been specified
Global Lake and River Ice Phenology Database
provided by National Snow and Ice Data Center (NSIDC)
Climate change (Primary topic)
Typology: Descriptive indicator (Type A - What is happening to the environment and to humans?)
- CLIM 020
Contacts and ownership
EEA Contact InfoPeter Kristensen
EEA Management Plan2008 2.3.1 (note: EEA internal system)
For references, please go to www.eea.europa.eu/soer or scan the QR code.
This briefing is part of the EEA's report The European Environment - State and Outlook 2015. The EEA is an official agency of the EU, tasked with providing information on Europe's environment.
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