Aberystwyth University Speedup and fracturing of George VI Ice Shelf, Antarctic Peninsula Holt, Thomas Owen; Glasser, Neil Franklin; Quincey, Duncan Joseph; Siegfrieg, Matthew Published in: Cryosphere DOI: 10.5194/tc-7-797-2013 Publication date: 2013 Citation for published version (APA): Holt, T. O., Glasser, N. F., Quincey, D. J., & Siegfrieg, M. (2013). Speedup and fracturing of George VI Ice Shelf, Antarctic Peninsula. Cryosphere, 7, 797-816. https://doi.org/10.5194/tc-7-797-2013 General rights Copyright and moral rights for the publications made accessible in the Aberystwyth Research Portal (the Institutional Repository) are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights. • Users may download and print one copy of any publication from the Aberystwyth Research Portal for the purpose of private study or research. • You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the Aberystwyth Research Portal Take down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim. tel: +44 1970 62 2400 email: [email protected] Download date: 10. Oct. 2021 EGU Journal Logos (RGB) Open Access Open Access Open Access Advances in Annales Nonlinear Processes Geosciences Geophysicae in Geophysics Open Access Open Access Natural Hazards Natural Hazards and Earth System and Earth System Sciences Sciences Discussions Open Access Open Access Atmospheric Atmospheric Chemistry Chemistry and Physics and Physics Discussions Open Access Open Access Atmospheric Atmospheric Measurement Measurement Techniques Techniques Discussions Open Access Open Access Biogeosciences Biogeosciences Discussions Open Access Open Access Climate Climate of the Past of the Past Discussions Open Access Open Access Earth System Earth System Dynamics Dynamics Discussions Open Access Geoscientific Geoscientific Open Access Instrumentation Instrumentation Methods and Methods and Data Systems Data Systems Discussions Open Access Open Access Geoscientific Geoscientific Model Development Model Development Discussions Open Access Open Access Hydrology and Hydrology and Earth System Earth System Sciences Sciences Discussions Open Access Open Access Ocean Science Ocean Science Discussions Open Access Open Access Solid Earth Solid Earth Discussions The Cryosphere, 7, 797–816, 2013 Open Access Open Access www.the-cryosphere.net/7/797/2013/ The Cryosphere doi:10.5194/tc-7-797-2013 The Cryosphere Discussions © Author(s) 2013. CC Attribution 3.0 License. Speedup and fracturing of George VI Ice Shelf, Antarctic Peninsula T. O. Holt1, N. F. Glasser1, D. J. Quincey2, and M. R. Siegfried3 1Centre for Glaciology, Institute of Geography and Earth Sciences, Aberystwyth University, Aberystwyth SY23 3DB, UK 2School of Geography, University of Leeds, Leeds LS2 9JT, UK 3Scripps Institution of Oceanography, UCSD, 9500 Gilman Drive, La Jolla CA 92093, USA Correspondence to: T. O. Holt ([email protected]) Received: 5 December 2012 – Published in The Cryosphere Discuss.: 24 January 2013 Revised: 9 April 2013 – Accepted: 11 April 2013 – Published: 6 May 2013 Abstract. George VI Ice Shelf (GVIIS) is located on the Doake et al., 1998), Larsen B (Rott et al., 2002; Glasser and Antarctic Peninsula, a region where several ice shelves have Scambos, 2008), Jones (Fox and Vaughan, 2005), Wordie undergone rapid breakup in response to atmospheric and (Reynolds, 1988; Vaughan, 1993) and Muller¨ (Ward, 1995). oceanic warming. We use a combination of optical (Landsat), During 1998, 2008 and 2009, the Wilkins Ice Shelf experi- radar (ERS 1/2 SAR) and laser altimetry (GLAS) datasets enced major breakup phases (Braun et al., 2009; Scambos et to examine the response of GVIIS to environmental change al., 2009; Padman et al., 2012) that highlighted the ongoing and to offer an assessment on its future stability. The spa- cryospheric response to atmospheric (Vaughan et al., 2003) tial and structural changes of GVIIS (ca. 1973 to ca. 2010) and oceanic (Martinson et al., 2008) warming. are mapped and surface velocities are calculated at different Ice-shelf stability on the AP has been linked to the south- time periods (InSAR and optical feature tracking from 1989 ward migration of a critical atmospheric thermal boundary to 2009) to document changes in the ice shelf’s flow regime. by a number of previous studies, linked to a rapid warming in Surface elevation changes are recorded between 2003 and the 1980s and 1990s. Morris and Vaughan (2003) remarked 2008 using repeat track ICESat acquisitions. We note an that the timing of ice-shelf collapse events was closely linked increase in fracture extent and distribution at the south ice to the arrival of the −9 °C mean-annual isotherm. During front, ice-shelf acceleration towards both the north and south 2000, this isotherm stretched from the Wilkins Ice Shelf em- ice fronts and spatially varied negative surface elevation bayment, across Alexander Island and George VI Ice Shelf change throughout, with greater variations observed towards (GVIIS), before extending along the AP to Jason Peninsula the central and southern regions of the ice shelf. We propose north of Larsen C Ice Shelf (Fig. 1). It has also been noted that whilst GVIIS is in no imminent danger of collapse, it is that ice shelves respond to variations in oceanic temperature vulnerable to ongoing atmospheric and oceanic warming and and circulation (e.g. Shepherd et al., 2004; Holland et al., is more susceptible to breakup along its southern margin in 2010; Bindschadler et al., 2011; Pritchard et al., 2012), and ice preconditioned for further retreat. through associated effects such as decreasing sea ice extents (Yuan and Martinson, 2000; Parkinson and Cavalieri, 2012) that may increase iceberg-calving rates from ice shelves through increased wave propagation (Brunt et al., 2011). At- 1 Introduction tributing specific ice-shelf changes to a single mechanism is still challenging, however, due to the complexity of ocean– 1.1 Background ice–atmosphere interactions. Several common glaciological characteristics have been In recent years, several Antarctic Peninsula (AP) ice shelves identified on those ice shelves that have recently exhibited have undergone dramatic and rapid retreat (Cook and breakup phases; ice-shelf collapse is typically preceded by Vaughan, 2010): for example, Prince Gustav Channel ice the following: (1) sustained ice-front retreat, resulting in a shelf (Rott et al., 1996; Cooper, 1997; Glasser et al., 2011), frontal geometry that bows inwards towards its centre from Larsen Inlet (Skvarca, 1993), Larsen A (Rott et al., 1998; Published by Copernicus Publications on behalf of the European Geosciences Union. 798 T. O. Holt et al.: Speedup and fracturing of George VI Ice Shelf -2000000 -1900000 -1800000 -1700000 100 km A Chapman PA Riley Millett ALM Bertram ER Willey Ryder North LA AN MB Ice Front Transition McArthur GoodenoughD Ü 0 Conchie 0 0 0 0 0 0 GT13 GT12 Eris JupiterPluto GT01 0 7 GT11 Grotto G 7 7 E 7 O R Haumea G E Eros E V I AL GT10 I EXANDE C ER IS Mars E GT02a LAN Saturn ND S GT02b H GT02c Kirwan Inlet E l Glaciers a L 0 nu 0 0 n F 0 E E 0 GVI Ice Front 2010 (Jan) a ) 0 0 0 0 N A N n 0 A 7 a 0 7 6 L 6 L G e 2 G -9W°C ImLeKanI aNnSnual isotherm m ( U U L C rm L I ° S I INCunEat aSk/ HbaEreL gFround e S S -9 th S NN H o H Grounded Ice is II N Faure Inlet N C Ice Shelf Area 2010 (Jan) C EE O O PP A A II S A Prince Gustav S DD T B GT03 T Larsen Inlet W e d d e l l B A C H RR n Larsen A S e a I C E EE VV t S H E L F GT04a Larsen B EE EKLUND a TT GT04b 0 N IISLANDS 0 r 0 J a s o n P e n i n s u l a O 0 0 0 0 c M 0 7 -9°C mean annual GT05 7 5 t 5 isotherm (2000) South i Muller c Ice Front GT06 P e n i n s Jones u Wordie l R o n n e GT07 a E n t r a n c e C a p e J e r e m y DE ATLEY IIS.. Wilkins GT08 B e l l i n g s h a u s e n SPATZ S e a Exttentt off A ISLAND GT09 0 500 km 0 0 0 0 0 0 0 7 7 4 4 -2000000 -1900000 -1800000 -1700000 Fig. 1. (A) George VI Ice Shelf with localities mentioned in the text and its key tributary glaciers. The names of tributary glaciers were taken from the Antarctic Place-names Committee (http://www.antarctica.ac.uk/apc/) except for those labelled “GT##” that were otherwise previously unnamed. Note the positioning of the −9 °C mean annual isotherm across Alexander Island (source: Morris and Vaughan, 2003). MB = Marguerite Bay. (B) The Antarctic Peninsula region displaying localities mentioned in the text, including the embayments of former ice shelves. both lateral pinning points (Doake et al., 1998); (2) contin- (Braun et al., 2009). It has also been suggested that extensive ued thinning from atmospheric or oceanic warming (Shep- meltwater on the ice-shelf surface acts as a driving force in herd et al., 2004; Fricker and Padman, 2012); (3) an increase fracture propagation that preconditions the ice shelf for rapid in flow speed (Rack et al., 2000; Rack and Rott, 2004; Vieli et retreat (Scambos et al., 2000, 2003; MacAyeal et al., 2003), al., 2007); and (4) structural weakening, typically along su- although the winter breakup events of the Wilkins Ice Shelf ture zones (Glasser and Scambos, 2008), but also transverse suggested that this is not a precursor for all collapse phases to flow due to changing stress regimes within the ice shelf (see Scambos et al., 2009).