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Climate: Are tropical storms migrating north?

Along with affecting the marine food chain, declining concentrations of phytoplankton in the oceans could impact global weather patterns.

Tropical cyclones appear to be migrating north.

Study finds that point of maximum intensity has moved poleward by 35 miles per decade

Staff Report

FRISCO — Tropical storm trackers say that the location where cyclones reach their maximum intensity is shifting north by about 35 miles each decade. The changes could put more coastal infrastructure at risk, while other areas that rely on tropical storms for water could be left high and dry, researchers said.

The amount of poleward migration varies by region. The greatest migration is found in the northern and southern Pacific and South Indian Oceans, but there is no evidence that the peak intensity of Atlantic hurricanes has migrated poleward in the past 30 years.

The amount of poleward migration is greatest in the northern and southern Pacific and South Indian Oceans, but there is no evidence that the peak intensity of Atlantic hurricanes has migrated poleward in the past 30 years.

By using the locations where tropical cyclones reach their maximum intensity, the scientists have high confidence in their results.

“Historical intensity estimates can be very inconsistent over time, but the location where a tropical cyclone reaches its maximum intensity is a more reliable value and less likely to be influenced by data discrepancies or uncertainties,” said Jim Kossin, the paper’s lead author, who is a scientist with NOAA’s National Climatic Data Center currently stationed at the NOAA Cooperative Institute for Meteorological Satellite Studies at the University of Wisconsin-Madison.

Consistent with this poleward shift, many other studies are showing an expansion of the tropics over the same period since 1980.

“The rate at which tropical cyclones are moving toward the poles is consistent with the observed rates of tropical expansion,” Kossin explained. “The expansion of the tropics appears to be influencing the environmental factors that control tropical cyclone formation and intensification, which is apparently driving their migration toward the poles.”

The expansion of the tropics has been observed independently from the poleward migration of tropical cyclones, but both phenomena show similar variability and trends, strengthening the idea that the two phenomena are linked. Scientists have attributed the expansion of the tropics in part to human-caused increases of greenhouse gases, stratospheric ozone depletion, and increases in atmospheric pollution.

However, determining whether the poleward shift of tropical cyclone maximum intensity can be linked to human activity will require more and longer-term investigations.

“Now that we see this clear trend, it is crucial that we understand what has caused it – so we can understand what is likely to occur in the years and decades to come,” said Gabriel Vecchi, scientist at NOAA’s Geophysical Fluid Dynamics Laboratory and coauthor of the study.

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