Global audience for NIWA’s lake research

THURSDAY, APRIL 2, 2015

Global audience for NIWA’s lake research

Holidaymakers knew it was a summer to remember, and science backed it up: the Rotorua lakes, some of New Zealand’s most popular, recorded their warmest temperatures in almost a decade over the peak summer months of January and February this year.

Interest in lake temperatures, however, runs deeper than summer fun and holiday swimming. Research by NIWA scientists on lake surface temperatures is informing global understanding of climate change, and New Zealand expertise has contributed to an article for Scientific Data, which is published by the leading environmental journal Nature.

NIWA Lake Scientist Piet Verburg said: “This summer has been unusually hot, resulting in very shallow mixed layers in lakes. As a result of the balmy conditions cyanobacterial blooms have occurred, even in nutrient-poor lakes where this is normally not seen such as Lake Tarawera, in the Bay of Plenty.”

Dr Verburg’s work, and the research of other NIWA scientists, is part of the Global Lake Temperature Collaboration (GLTC), an international group assembled to provide better access to global lake temperature records. The GLTC project was established in 2010 to build a global database of lake surface temperatures, including both satellite data and “on the ground” measurements from collection programmes such as NIWA’s.

It is now widely recognised that global and regional climate change has important implications for aquatic ecosystems. Recent studies have revealed significant warming of lakes and reservoirs throughout the world.

The observed rate of lake warming is sometimes greater than that of ambient air temperature. Rapid changes in lake temperature have profound implications for hydrology, productivity, and biotic communities.

New Zealand has about 3820 lakes with a surface area greater than one hectare, and NIWA and regional councils collect lake temperature data for about 120 of them, from Lake Taupo, the North Island’s largest lake to Lake Okareka, one of the smallest. The data is valued globally as there are fewer lakes in the Southern Hemisphere than the Northern, and these datasets broaden the global reference.

The GLTC project started as a small group of 10 people from three countries, and has grown to include more than 70 investigators from 20 countries worldwide. Its database of 291 lakes and reservoirs worldwide provides summer mean lake surface temperatures from 1985-2009, and roughly doubles the amount of data available from satellites alone.

This new dataset represents the first publicly available global compilation of in-situ and satellite-based lake surface temperature data. The GLTC database also provides information on climatic drivers (air temperature, solar radiation, cloud cover), as well as geomorphometric characteristics that may affect lake temperature (latitude, longitude, elevation, lake surface area, maximum depth, mean depth, volume).

This unique global dataset will offer an invaluable baseline perspective on lake thermal conditions for ongoing and future studies of environmental change.

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