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The Combined Influence of ENSO and SAM on Antarctic Climate Variability in Austral Spring

Clem, Kyle R.
http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1396540411

Abstract Details

2014, Master of Science (MS), Ohio University, Geography (Arts and Sciences).
Recent studies have identified significant warming trends across West Antarctica and the Antarctic Peninsula, which is likely linked to tropical forcing. Consistent with the warming trends are significant changes in sea ice concentration in the Ross, Amundsen, and Bellingshausen Seas. This study investigates changes in the regional circulation associated with the Amundsen-Bellingshausen Seas Low (ABSL) and the role that these changes have on the temperature trends during austral spring. Further, this study investigates temporal variations in El Niño-Southern Oscillation (ENSO)-related tropical forcing and Southern Annular Mode (SAM)-related forcing on the ABSL and the regional climate during austral spring. Based on gridded climatological data, a statistically significant deepening of the ABSL in the Ross Sea region and increases in pressure/geopotential height to the northeast of the Antarctic Peninsula during austral spring over the period 1979-2012 is detected. Consistent with these trends are a strengthening of the meridional winds, with increased warm (cold) air advection onto western West Antarctica (the Ross Sea) associated with the deepening pressure in the Ross Sea region, and increased warm air advection onto the western Antarctic Peninsula associated with the strengthening high pressure to the northeast of the Peninsula. The ABSL trends in the Ross Sea are likely related to outgoing longwave radiation (OLR) in the Niño 1+2 region in the far eastern tropical Pacific, and the pressure/geopotential height trends to the northeast of the Antarctic Peninsula are likely associated with trends in the Southern Oscillation Index (SOI), a measure of ENSO variability. Based on these connections, more than half of the warming along the Antarctic Peninsula is congruent with trends in the SOI (towards more La Niña-like conditions), while nearly half of the warming across western West Antarctica is congruent with trends in the Niño 1+2 region. This study also finds a spatial and temporal dependency regarding the impacts that SAM and ENSO have on the Antarctic Peninsula during austral spring: relationships with ENSO and Antarctic Peninsula climate are persistent and statistically significant across the western Peninsula, while relationships with the SAM are persistent and statistically significant across the northeastern Peninsula. Other ENSO/SAM-Peninsula temperature correlations appear weak over the full period of record as they vary temporally, fluctuating in response to changing correlations between the SAM index and SOI in austral spring. Changes in the SOI-SAM correlations are due primarily to the 1988 La Niña/SAM negative event, which significantly altered the location of the ENSO teleconnection in the South Pacific Ocean and, therefore, its influence on the regional climate. Whether or not there is decadal variability in the ENSO-SAM relationship remains unclear; however, it is evident that the influence across the Peninsula varies in both space and time, related to the strength and spatial extent of the response in the Amundsen-Bellingshausen Seas. This suggests that in order to accurately attribute the regional warming to ENSO-related tropical forcing, it is necessary to consider the role of the regional circulation manifested by the phase of each climate mode together.
Ryan Fogt (Advisor)
Dorothy Sack (Committee Member)
Thomas Smucker (Committee Member)
182 p.
Climate Change; Meteorology
ENSO; SAM; teleconnection; Antarctica; climate

Recommended Citations

Citations

  • Clem, K. R. (2014). The Combined Influence of ENSO and SAM on Antarctic Climate Variability in Austral Spring [Master's thesis, Ohio University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1396540411

    APA Style (7th edition)

  • Clem, Kyle. The Combined Influence of ENSO and SAM on Antarctic Climate Variability in Austral Spring. 2014. Ohio University, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1396540411.

    MLA Style (8th edition)

  • Clem, Kyle. "The Combined Influence of ENSO and SAM on Antarctic Climate Variability in Austral Spring." Master's thesis, Ohio University, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1396540411

    Chicago Manual of Style (17th edition)

ohiou1396540411
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This open access ETD is published by Ohio University and OhioLINK.