The influence of the Amundsen Sea Low on the winds in the Ro

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TitleThe influence of the Amundsen Sea Low on the winds in the Ross Sea and surroundings: Insights from a synoptic climatologyAbstractThe Amundsen Sea Low (ASL) is an area of climatologically low atmospheric pressure situated over the Southern Ocean. The depth and location of this feature have significant effects on winds, temperature, moisture transport, and sea ice in its vicinity. In this article, we quantify the modulating effect of this feature on winds over the Ross Sea and Ross Ice Shelf. We examine composites of surface winds sampled according to extrema in ASL depth, longitude, and latitude. We employ the output of a previously developed synoptic climatology to identify the explanatory synoptic-scale forcings. In autumn, winter, and spring (AWS) we find that the impact of the depth of the ASL is smaller than that of its location. The ASL moves eastward when it is deep, thereby reducing its influence on Ross Sea winds. When the ASL is northward, we find strongly enhanced southerly flows over the Ross Sea and Ice Shelf, forced by greater cyclonic activity in the north of the Ross Sea. In summer, we find increased cyclonic flow coinciding with a deeper ASL, despite the ASL being located in the Bellingshausen Sea at this time. The responses to the ASL longitude and latitude are profoundly different to those in AWS, suggesting that relationships are strongly dependent on the varying seasonal location of the low. We examine two metrics of the ASL depth and identify that the absolute mean sea level pressure (MSLP) has a more widespread response than that of the relative MSLP. Copyright2015. American Geophysical Union. All Rights Reserved.AcknowledgementsThe authors wish to thank John Cassano, Ryan Fogt, and two anonymous reviewers for their valuable input on this study. Thanks also go to James Renwick and Andrew Orr for their insightful comments on an early version of this work. This study was supported by a grant from the New Zealand Antarctic Research Institute, a University of Canterbury Doctoral Scholarship, and a New Zealand Ministry of Foreign Affairs and Trade Ross Sea Dependency Scholarship. ERA-Interim output was downloaded from the European Centre for Medium-Range Weather Forecasts data server (http://apps. ecmwf.int/datasets/), the Marshall SAM index from the British Antarctic Survey (http://www.antarctica.ac.uk/met/ gjma/sam.html), the SOI from the University Corporation for Atmospheric Research (http://www.cgd.ucar.edu/ cas/catalog/climind/soi.html), and the Nino 3.4 index from the National Center for Atmospheric Research (http://www.cgd.ucar.edu/cas/catalog/ climind/Nino_3_3.4_indices.html).

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1st AuthorCoggins, J.AuthorCoggins, J.McDonald, A.Year2015JournalJournal of Geophysical Research AtmospheresVolume120Number6Pages2167-2189DOI10.1002/2014JD022830URLhttps://www.scopus.com/inward/recor.....f31209cd6f658645fb4368362Keywordscompositecyclonedepthgeographical variationice shelfquantitative analysissea level pressuresurface windsynoptic meteorologywind direction, Amundsen SeaBellingshausen SeaRoss SeaSouthern Ocean, rank3Author KeywordsAmundsen Sea LowAntarcticacycloneRoss Ice Shelfsurface windProgrammeK055 - Dynamics in the Antarctic Middle Atmosphere - MF calibration

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TypeArticleCitationCoggins, J. and McDonald, A. (2015). The influence of the {Amundsen Sea Low} on the winds in the {Ross Sea} and surroundings: Insights from a synoptic climatology. Journal of Geophysical Research Atmospheres, 120(6): 2167-2189 IdentifierCoggins2015Relevancerank3

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K055 - Dynamics in the Antarctic Middle Atmosphere - MF calibration