Ice dynamics from Earth observations Twila Moon Bristol Glaciology Centre Geographical Sciences University of Bristol twila.moon@bristol.ac.uk www.twilamoon.com 1
When you have mapped the ice sheets once your career will be over because they don t change very quickly. - A well- known glaciologist, circa 1995 ice sheet ocean ice sheet bed 2
2005-2010 2000-2005 GF GF GF XYXY N XY ^_ GF GF U XY ") ")XY N XY Velocity 10 100 (m/yr) 1000 Velocity 10 scale 100 (m/yr) 1000 3
First look at Greenland glacier velocities 15 Jakobshavn Isbræ Velocity (km/yr) 10 5 Up glacier Terminus 0 0 30 60 Distance along glacier (km) [Joughin et al., Nature, 2004] 4
First look at Greenland glacier velocities 12 Helheim Glacier Velocity (km/yr) 9 6 3 0 20 Distance along glacier (km) 40 [Howat et al., GRL, 2005] 5
First look at Greenland glacier velocities 14 Kangerdlugssuaq Glacier Velocity (km/yr) 7 0 0 20 40 Distance along glacier (km) [Howat et al., Science, 2007] 6
Rapid speedup in Antarctica [Scambos et al., GRL, 2004] 7
Projections for future sea level rise [IPCC 2007] 8
Projections for future sea level rise Dynamical processes related to ice flow not included in current models Understanding of these processes is limited and there is no consensus on their magnitude. [IPCC 2007] 9
Impacts of ice mass loss 6 m 60 m 10
Local to global impacts of ice sheet change 6 m 60 m 11
Local to global impacts of ice sheet change 6 m 60 m 12
Focus on areas of large, rapid change!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!( 2005-2010!( 2000-2005!(!(!(!(!(!(!(!(!(!(!( GF GF GF!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!( GF XYXY!(!( N XY ^_ GF XYXY XY XY XY GF GF NW U!(!(!(!(!(!( ") XY!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!( ")XY N XY Velocity 10 100 (m/yr) 1000 Velocity 10 scale 100 (m/yr) 1000 13
A connected ice- ocean system glacier & fjord topography terminus change hydrologic system velocity ice mélange & sea ice fjord & ocean characteristics ice sheet bed & bathymetry 14
Multi- year velocity changes 2000-2010 changes: 28% speedup 34% speedup 15
Widespread retreat (1992/93-2009/10) Terminus change 10+ km retreat 7 to 10 km retreat 4 to 7 km retreat 1 to 4 km retreat Advance/retreat <1 km 1+ km advance [Data available: NSIDC] 16
Local variability in space and time 2010 to 2011 Percent annual velocity change [modified from Moon et al., Science, 2012] 17
Local variability in space and time 2010 to 2011 Percent annual velocity change [modified from Moon et al., Science, 2012] 18
Improving temporal resolution 19
Long- term speedup linked to retreat Mean velocity (m/yr) Mean terminus position (m) 20 [Moon et al., JGR, 2015]
Seasonal patterns respond to different forcing? Mean velocity (m/yr) Mean terminus position (m) 21 [Moon et al., JGR, 2015]
Seasonal terminus change sea ice link Mean terminus position (m) [Moon et al., JGR, 2015] 22
Hydrology- induced speedup Distributed and inefficient system Increasingly efficient Efficient and channelized system Ice flow direction [Carr et al., 2013] [Diagrams: I. Hewitt] 23
Distinct seasonal velocity patterns Relative measured Relative measured velocity (m/yr) velocity (m/yr) 500 250 500 0 250-250 -500 0-250 a) Type 1 b) Type 2 c) Type 3 2009 2010 2011 2012 2013 a) Type 1 b) Type 2 c) Type 3 2009 2010 2011 2012 2013 + 0-500 Jan-1 Jul-1 Dec-31 Jan-1 Jul-1 Dec-31 Jan-1 Jul-1 Dec-31 40 + Date of year 40 20 Runoff (kg m -2 day -1 ) Date of year 24 [Moon et al., GRL, 2014]
Velocity linked to terminus change Relative measured velocity (m/yr) 500 250 0-250 a) c) Type 13 b) Type 2 c) Type 3 2009 2010 2011 2012 2013 faster speed spring position -500 Dec-31 Jan-1 Jul-1 Dec-31 40 20 0 + Runoff (kg m -2 day -1 ) Date of year [Moon et al., GRL, 2014] 25
Velocity linked to subglacial hydrology a) b) Type 12 b) c) Type 23 c) Type 3 + Dec-31 Jan-1 Jul-1 Dec-31 Jan-1 Jul-1 Dec-31 Date of year + Date of year 40 20 0 Runoff (kg m -2 day -1 ) [Diagrams: I. Hewitt] [Moon et al., GRL, 2014] 26
Velocity linked to subglacialhydrology a) Type 1 b) Type 2 c) Type 3 + Jan-1 Jul-1 Dec-31 Jan-1 Jul-1 Dec-31 Date of year 40 20 0 Runoff (kg m -2 day -1 ) [Diagrams: I. Hewitt] 27 [Moon et al., GRL, 2014]
Velocity reflecting surface melt changes 2010 & 2012 response 2012 response 28
More improvements in space/time measurements Landsat 8 to ice surface velocity (globally). [Fahnestock et al., RSE, 2015] 29
Multiple satellites on the task Sentinel 1 radar-derived velocities. [Nagler et al., RS, 2015] 30
From regional to ice sheet wide analysis 200 km 31
From regional to ice sheet wide analysis 2014 200 km 200 km 32
Answering questions across space and time 4000 3500 Velocity (m/yr) Velocity (m/yr) 3000 2500 2000 1500 1000 500 2013 2013.5 2014 2014.5 2015 2015.5 Differences during 2014 summer to fall: (May 24-June 9) to (Sep 6-Sep 22) 33
Answering questions across space and time 4000 3500 Velocity (m/yr) Velocity (m/yr) 3000 2500 2000 1500 1000 500 2013 2013.5 2014 2014.5 2015 2015.5 Differences during 2014 summer to fall: (May 24-June 9) to (Sep 6-Sep 22) 34
Progress at all scales. For example Location & timing Understanding mass loss & freshwater flux Predicting sea level rise 35
New projections of future sea level rise New projections of future SLR RCP8.5 (high) 2007 IPCC high RCP2.6 (low) [IPCC 2013] 36
New projections of future sea level rise New projections of future SLR RCP8.5 (high) 2007 IPCC high RCP2.6 (low) Many of the IPCC 2013 conclusions regarding sea level rise and mass loss from ice sheets only have medium confidence. [IPCC 2013] 37
Expect more velocity changes to come [Paolo et al., Science, 2015] 38
Look where others aren t 2007-14 compared to 1985-94 [Tedstone et al., Nature, 2016] 39
Thank you & be in touch! Twila Moon Bristol Glaciology Centre Geographical Sciences University of Bristol twila.moon@bristol.ac.uk www.twilamoon.com 40