This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5). The West Antarctic Peninsula (WAP) is the one region of the Antarctic continent that is unequivocally warming, and as such is associated with the mobilization and loss of major ice shelves, as has been recently observed for the Larsen B (2002) and Wilkins Ice Shelf (2008). The Amundsen/Bellingshausen Seas Low (ABSL) is a sub-synoptic, often persistent low-pressure weather system that leads to sustained west-northwesterly airflows across the WAP region. Long term changes in the strength and position of the ABSL, its teleconnection with large scale climate modes such as the Southern Annular Mode (SAM) and the El-Nino Southern Oscillation (ENSO), and its interaction with the polar vortex are suspected to be important factors in attribution of Antarctic climate change currently being dramatically observed in the WAP. Because of the paucity of reliable observations in this extremely remote area of the continent, much remains that is uncertain
Existing satellite-era observational data (since 1979), along with reanalysis sets, will be examined to shed better definition of the variability in position and intensity of the ABSL as a weather feature. Several modeled data sets, from a range of mesoscale and climatological models (e.g. Polar MM5, AMIP, CCM CAM3, HadAM3, ECHAM4.5) will also be examined at the regional scales appropriate to the ABSL to better describe the large scale influences of climate patterns such as ENSO and SAM. Finally an assessment of the effects variability in the ABSL may have on the regional West Antarctic climate will be made.
The Amundsen-Bellingshausen Seas Low (ABSL) is a semi-permanent region of low atmospheric pressure off the coast of West Antarctica, sitting approximately above the Amundsen and Bellinghausen Seas. Over the last three years of this project, the characteristic variability of the ABSL has been investigated thoroughly, as well as processes that influence this variability. Further, the connection of the ABSL to the regional climate across the Antarctic Peninsula and West Antarctica has been detailed. Significant advances in scientific understanding as a result of this project include: a) the ABSL has a marked seasonal cycle in its intensity and location, being farthest poleward in winter and farthest east (west) during austral summer (winter). It reaches its greatest depth during late austral winter through austral spring (Fogt et al. 2012a; Figure 1); b) the ABSL position and intensity is strongly modulated by the underlying synoptic-scale activity (Fogt et al. 2012a; Figure 2); c) the cyclones in the Ross Sea have been increasing in intensity during austral spring, leading to a deeper ABSL in this season. The location of the stronger ABSL, through implied geostrophic temperature advection, is consistent with the ongoing warming in West Antarctica in spring (Fogt et al. 2012a; Figure 3); d) The zonally asymmetric structure of the Southern Annular Mode (SAM), and particularly its high southern latitude component, influences the location and intensity of the ABSL. The asymmetric component of the SAM, and hence the ABSL, has strong connections with the temperatures across the Antarctic Peninsula (Fogt et al. 2012b; Figure 4); e) The influence of the El Niño – Southern Oscillation (ENSO) and the SAM act to change the overall spatial extent of the ABSL. During times of La Niña occurring with positive SAM events, or El Niño occurring with negative SAM events, the spatial extent of the ABSL is larger, so that there are uniform ENSO- and SAM-related climate impacts across the Antarctic Peninsula in austral spring (Clem and Fogt, 2014; Figure 5); f) Stratospheric ozone depletion appears to only have a significant impact on the changes in the ABSL in the troposphere in austral summer, while changes in the stratosphere above the ABSL are also observed in austral spring (Zbacnik and Fogt, in review; Figure 6). Intellectual Merit The project has investigated the role of the atmospheric circulation in explaining the ongoing warming and ice loss across West Antarctica and the Antarctic Peninsula. As little has been known on the patterns of the atmospheric circulation in this data sparse region, the project has provided important fundamental knowledge on this circulation variability, and how this variability is tied to the better understood patterns of large-scale climate, such as ENSO and the SAM. Further, the project has shown that at least part of the warming in West Antarctica during austral spring is consistent with changes in the ABSL and the underlying synoptic scale cyclones in the Ross Sea: as these cyclones have been intensifying in this region, a greater magnitude of warm air advection has occurred onto West Antarctica. The project also established links between the ABSL, ENSO, SAM, and the climate of the Antarctic Peninsula in austral spring. Building upon previous work that detailed the position and intensity of the ABSL, the paper by Clem and Fogt (2013) demonstrated that the breadth / spatial extent of the ABSL is also important to consider, as this dictates the extent of the ENSO influence beyond the western Antarctic Peninsula, and the SAM influence beyond the northeastern Antarctic Peninsula. While it is becoming more evident that the ABSL is modulated by large-scale patterns of internal / natural climate variability, it is much less clear of an anthropogenic influence. Particularly, only during austral summer is there a discernible influence of stratospheric ozone depletion on changes in the ABSL magnitude. Broader Impacts The project has trained a total of 6 undergraduate students on research methods, scientific writing, and scientific presentations. All but one of the undergraduate students have pursued graduate education. The project has also included research conducted in part by five graduate students. The work has been presented at numerous conferences, both domestic and international, and in three publications to date (one additional publication is currently under review). The project also involved two female scientists, a minority in the atmospheric sciences. The results have also been disseminated to the Athens community. Polar climate change and results from this work were presented to middle school earth science classrooms at six different schools across southeast Ohio. Other lectures on climate change given by the PI to the Athens and Ohio University communities have also incorporated elements of this research project. A final outreach event is planned at the Athens Public Library in February 2014.
