Study aims to fathom El Nino effect

Scientist Heidi Roop recovers scientific data sensors at Lake Ohau. Photo supplied.
Scientist Heidi Roop recovers scientific data sensors at Lake Ohau. Photo supplied.
If a new scientific study goes to plan, Lake Ohau in North Otago could provide a better understanding of how systems like the El Nino climate pattern drive the New Zealand climate.

United States scientist Heidi Roop began a three-year study of the lake in March, after being awarded GNS Science's Sarah Beanland Memorial Scholarship, and already the former US Geological Survey member said she was "reasonably confident" samples taken from the lake bed would help create a record of weather patterns for at least 1000 years.

Ms Roop said the study, which forms part of her PhD studies at Victoria University, and is in collaboration with national and international research institutes, would investigate the relationship between large-scale climate systems like the El Nino southern oscillation and New Zealand's climate patterns, and could provide a better understanding of southern hemisphere weather.

A high sediment inflow meant that sediment layers at Lake Ohau could be likened to the rings of a tree and provided a "preserved and detailed" record of annual climate variations, she said.

"We want to know if major storm events are recorded at the outflow, or if we are missing periods of time and significant events, such as earthquakes, that might help us to compile a detailed annual climate record.

"The beauty of Lake Ohau sediment is that you have precise time markers seemingly at annual intervals. I hope to be able to say something meaningful about each annual package of sediment for the past 1000 years.

"Previous work on Lake Tekapo suggested that the sediment layering there is not annual and quite complicated, making it difficult to use those sediments for a detailed reconstruction of climate. Many different lakes can be used to study climate in this way, but finding a lake that can provide reliable information on an annual basis back thousands of years is uncommon, and makes the Lake Ohau record unique in the region."

El Nino occurrences are associated with a rise or fall in sea temperatures in the Pacific Ocean, and can affect where tropical cyclones hit land.

Studying Lake Ohau could result in a better understanding of the impact of El Nino and other large climate systems.

"We anticipate that changes in precipitation will be a primary driver of changing sedimentation in Lake Ohau. If this is true, we hope to provide information about how the timing and amount of precipitation has changed in the past. Precipitation in New Zealand is driven, in part, by large-scale climate systems like El Nino and the latitudinal position of the westerly winds, thus allowing us to learn about how these features behaved in the past."

GNS quaternary paleoclimate scientist Dr Marcus Vandergoes said Ms Roop's work was a "key component" in a scientific collaboration studying how climate change has affected the frequency and magnitude of storm events and hydrology in the South Island.

"This type of research is essential to broaden our knowledge of the potential impact of climate change in the future."

Although the final findings would not be known for another three years, initial samples, collected every three months, had "been in line with expectations", Ms Roop said.

A website was also being developed to keep local residents informed of progress.

- andrew.ashton@odt.co.nz

 

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