New research reveals history of South Pacific Convergence Zone

Philippa Higgins undertaking research in the South PacificUNSW Civil and Environmental Engineering PhD student Philippa Higgins has published new research on the South Pacific Convergence Zone (SPCZ), using moisture‐sensitive tree‐ring records to understand the long‐term behaviour of the SPCZ, and how it may change under future climate conditions.

The paper, titled 'One Thousand Three Hundred Years of Variability in the Position of the South Pacific Convergence Zone', addresses the significant rainfall variability that South Pacific island communities experience between seasons, across years, and between decades. The variability is due to changes in the average position and intensity of the SPCZ, the largest rain belt in the Southern Hemisphere. The SPCZ tends to move from east to west in response to changes in sea surface temperatures and winds that accompany the El Niño‐Southern Oscillation. Lower frequency variability is also present in the SPCZ; however, this variability is poorly understood because data records from the region are too short.

In this research, Philippa and her colleagues extended the record of SPCZ variability back in time to 700 CE using a statistical model based on moisture‐sensitive tree‐ring records from both sides of the Pacific. They analysed the SPCZ reconstruction during periods when the average climate conditions were different from today and assessed the impact that changes in solar output and volcanic eruptions may have had during these periods. This research helps to understand the long‐term behavior of the SPCZ, which is essential to understand how it may change under future climate conditions.

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