Changing weather patterns
“Since 1950, there has been 0.4 to 0.7°C warming, with more heatwaves, fewer frosts, more rain in south-west New Zealand, and less rain in north-eastern New Zealand. New Zealand is already experiencing impacts from recent climate change… These are now evident in increasing stresses on water supply and agriculture, changed natural ecosystems, reduced seasonal snow cover, and glacier shrinkage.”
– IPCC 4th Assessment on climate change impacts for New Zealand (2007).
While the quote is more than a decade old, the message remains the same: rising concentration of greenhouse gasses (GHG) in the atmosphere is changing weather patterns globally and locally. These GHGs trap heat in the atmosphere. More heat = more energy, turbo-charging atmospheric weather events and leading to ‘weather bombs’. Storms become more intense, so flooding is more frequent and intense. On the opposite end of the scale, droughts are harsher and evapotranspiration increases, affecting plants. Winter snowpack and glacial mass in New Zealand is decreasing rapidly, leading to a change in river flows.
In February 2018, temperatures in Siberia reached 35°C above average. In August 2019, the Greenland ice sheet was \’in the throes of one of its greatest melting events ever recorded\’, while heat-driven wildfires broke out in Siberia and Greenland. These changes in temperatures alter the way global weather behaves, sometimes leading to unexpected outcomes, for example, the ‘wobble’ in the polar vortex leading to massive temperature swings across North America. A similar \’wobble\’ to the jetstream in the Southern Hemisphere also impacts the weather we experience in New Zealand.
The impacts of higher temperatures also affect the weather in the ocean, and with it, the oceanic food web. What has now become known as a ‘marine heatwave’ was responsible for killing millions of fish, marine mammals, and seabirds in 2017. That affects the availability of food for river birds that depend on oceanic and coastal ecosystems over winter.
Marine heatwaves are now predicted to become the new normal.
Why is it a problem for braided rivers?
\”A 41-year record of the endemic red-billed gull (Larus novaehollandiae scopulinus, a medium-sized inshore feeder on krill) shows that its breeding success is positively related to krill abundance, which is, in turn, positively related to the La Niña (or positive phase of the ENSO cycle) when winter conditions are stable, and upwelling associated with northeasterly winds in late spring (Mills et al. 2008). Recent changes in the PDO and El Niño (negative) phase ENSO events led to a more than 50% decline in red-billed gulls between 1983 and 2003.\”


Research and references
Below are references to material specifically used in this page or are of direct relevance. If you are interested in this topic, for the latest information we recommend Climate Central or the journal Nature Climate Change.
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National Science Challenges: projects | 2019: Paulik et al (NIWA); New Zealand Fluvial and Pluvial Flood Exposure
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2019 (July) NIWA: 2019 so far – a story of weather and climate extremes
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2019: NIWA Our Changing Oceans
- 2019: Greenland ice sheet record melting
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2019: Cornwall; Ocean heat waves like the Pacific’s deadly ‘Blob’ could become the new normal
Science magazine editorial
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2019: Beaugrand; Prediction of unprecedented biological shifts in the global ocean. Nature Climate Change 9, 237-243
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2019: Smale et al; Marine heatwaves threaten global biodiversity and the provision of ecosystem services. Nature Climate Change 9, 306–312
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2018: Thin Ice (interactive explanation of New Zealand\’s declining glaciers)
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2018: Siberia burning (NASA/Climate Central)
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2018: Renner and Zohner; Climate Change and Phenological Mismatch in Trophic Interactions Among Plants, Insects, and Vertebrates; Annual Review of Ecology, Evolution, and Systematics Vol. 49:165-182
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2018: Keogan et al; Global phenological insensitivity to shifting ocean temperatures among seabirds. Nature Climate Change, 2018; 8 (4)
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2015: Paleczny et al; Population Trend of the World’s Monitored Seabirds 1950-2010, Plos One June 9, 2015
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2014: Constable et al; Climate change and Southern Ocean ecosystems I: how changes in physical habitats directly affect marine biota. Global Change Biology Oct; 20(10) pp3004-25
- 2011: McGlone and Walker (DOC) Potential effects of climate change on New Zealand’s terrestrial biodiversity and policy recommendations for mitigation, adaptation and research
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2010: Hoegh-Guldberg & Bruno; The Impact of Climate Change on the World’s Marine Ecosystems; Science Vol. 328, Issue 5985, pp. 1523 -1528
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2007: IPCC 4th Assessment on climate change impacts for New Zealand