Long term trends in extreme daily temperature and precipitation on sub-Antarctic Marion Island from 1950 to 2020
Loading...
Date
2024
Authors
Kabase, Zenande
Journal Title
Journal ISSN
Volume Title
Publisher
University of Fort Hare
Abstract
Sub-Antarctic Marion Island (46° 54’ S, 37° 53’ E) has experienced notable changes due to global climate change in recent decades. Records indicate a gradual increase in mean annual air temperature, with a rise of 2.4°C per century. Both maximum and minimum temperatures have increased by over 1°C, while annual rainfall has decreased to less than 2000 mm over the past seventy-one years. The onset of extreme events in the Antarctic Peninsula and subAntarctic region was observed in the early 2000s, and forecasts suggest these events will become more frequent, intense, and prolonged in the future. The objective of this study was to analyse the trends and patterns of daily extreme climatic parameters, specifically air temperature and precipitation, on Marion Island from 1950 to 2020. This analysis aimed to contextualize these changes within the observed alterations in the island's synoptic weather, providing insight into the underlying drivers. Daily temperature and precipitation data were obtained from the South African Weather Service (SAWS) and analysed. Linear regression statistics were employed to evaluate trends and patterns in the daily extremes, utilizing 25 extreme indices developed by the Expert Team on Climate Change Detection Indices (ETCCDI). The results spanning 71 years revealed a consistent climate shift on Marion Island. Mean annual air temperatures and daily maximum temperatures increased by 1.2°C (p < 0.01), while daily minimum temperatures rose by 0.9°C (p < 0.01). There was a significant rise in warm spells (p < 0.05) and warm nights (p < 0.01), accompanied by a notable decrease in cold spells (p < 0.01), cold nights, and annual frost days. The annual precipitation trend indicated a decline, with a significant reduction of 1042.3 mm (p < 0.01) in mean annual rainfall, along with a decrease in heavy precipitation events over the study period. Additionally, the occurrence of consecutive dry days increased by an average of 5 to 7 days between 1950 and 2020. Anthropogenic forcing, particularly the positive phase of the Southern Antarctic Mode, is identified as the primary cause of ocean and atmospheric warming in the sub-Antarctic region. The positive shift of the Southern Antarctic Mode due to anthropogenic forcing is a significant impact of how climate change is affecting the region and surrounding areas, and how frequent the phase could be due to an intensification of climate change conditions in the region. This phenomenon leads to the intensification and poleward migration of the Southern Hemisphere westerly winds. Changes in wind patterns, such as prolonged exposure to warm north-westerly winds and reduced exposure to post-cold front sectors associated with passing cyclones, likely contribute to the observed trends in temperature extremes and precipitation on Marion Island. Continued elevation of daily air temperature extremes and reduction in daily precipitation extremes may result in abnormal warming, further deglaciation, further retreat of the permanent snowline, disruption of soil frost and needle ice processes, and prolonged drying of the mires on this periglacial sub-Antarctic island.
Description
Masters dissertation
Keywords
Marion Island (Prince Edward Islands), Temperature, Climatic changes -- Antarctic regions, Precipitation (Meteorology) -- Antarctic regions
Citation
Kabase, Z. (2024) Long term trends in extreme daily temperature and precipitation on sub-Antarctic Marion Island from 1950 to 2020. MSc (Geography) dissertation. Alice, South Africa: University of Fort Hare.