PROGRESS IN ICESHEET MONITORING USING SENTINEL SATELLITES

Transcription

1 Polar Space Task Group PROGRESS IN ICESHEET MONITORING USING SENTINEL SATELLITES Thomas Nagler, Helmut Rott, Markus Hetzenecker, Jan Wuite / ENVEO Contributions by Dana Floricioiu / DLR Anders Kusk / DTU

2 Greenland Ice Sheets CCI Team: IV: Ice velocity costal regions + select areas (phase 1), all ice sheet (ph. 2) SEC: Surface elevation changes, ERS/Envisat/CryoSat, 1991-present GLL: Grounding lines from SAR, main northern floating glaciers 1991-present CFL: Calving front locations main outlet glaciers 1991-present GMB: Gravimetric mass balance from GRACE (phase 2, starting 2015) ECV grid/line data SEC IV GLL CFL GMB - Horizontal resolution 5 km 500 m 200 m 200 m 50 km - Temporal resolution 1 yr 1 yr (S1) 5 yr 1 yr 1 month - Accuracy 0.1 m/yr 20 m/yr 1 km 200 m? Jakobshavn Glacier front PSTG 5 th Session, 5-7 Oct Nagler & Rott 2

3 Antarctic Ice Sheet CCI Team: Products PSTG 5 th Session, 5-7 Oct Nagler & Rott 3

4 Public outreach: DMI-DTU-GEUS Monthly mass loss (GMB) Daily ice sheet melt (met model) PSTG 5 th Session, 5-7 Oct Nagler & Rott 4

5 PSTG 5 th Session, 5-7 Oct Nagler & Rott 5

6 Greenland Ice Sheet Surface Velocity Sentinel-1 January March tracks with 3 repeat acquisitions ~800 slices ~25000 bursts IV Product v E, v N, v dz 250 m pixel spacing Nagler, Rott, Hetzenecker, Wuite & Poutin, The Sentinel-1 Mission: New Opportunities for Ice Sheet Observations. Rem. Sens PSTG 5 th Session, 5-7 Oct Nagler & Rott 6 6

7 Sentinel 1 Ice Surface Velocity & Comparison to TSX and PALSAR S Jan days 3-15 TSX, Dec-Feb / 22 days 11 days image pairs PalSAR, Dec2009, 46 days PalSAR, Aug days PSTG 5 th Session, 5-7 Oct Nagler & Rott 7 7

8 Length-Profiles S1 versus TSX & PALSAR Store Glacier and Umiammakku Glacier A B A B A B PSTG 5 th Session, 5-7 Oct Nagler & Rott 8 8

9 S1 Acquisition Strategy for Margins Track 090 by T. Nagler / ENVEO, agreed by R. Forsberg / DTU, and B. Scheuchl / UCI S1 Tracks for Greenland Margins, acquired every Cycle of 12 days (total year) in IW mode: Track 026 Track 074 Track 090 Track 112 Track 141 Track 170 The same tracks should also be acquired during the campaigns with Full coverage of Greenland June 2015 Implemented by ESA Thomas 16-17/1/2012 Nagler Icesheet 9 PSTG 5 th Session, 5-7 Oct Nagler & Rott 9

10 Monitoring Greenland Margins with Sentinel-1 Products: Ice Velocity Calving Front Grounding Line (?) ERS /ENVISAT Thomas Nagler PSTG 5 th Session, 5-7 Oct Nagler & Rott 10 10

11 Monitoring Greenland Margins with Sentinel-1 Thomas Nagler PSTG 5 th Session, 5-7 Oct Nagler & Rott 11 11

12 Sentinel-1 Acquisition Strategy - Greenland Revised - Icesheet wide Coverage: 1 Annual Campaign (Dec-Mar: 8 consecutive acquisitions), includes the tracks used for monitoring the margins (replaces previous proposal: 2 annual campaigns (Sept-Oct; Jan-Mar) each 4 repeat aqcuisitions). - This will increase the probability for complete icesheets wide IV coverage significantly - To be extended to Arctic Icecaps - Continous monitoring of Greenland margins (every cycle) using 6 tracks (implemented by ESA since June 2015) - Enables continous short term variations of ice dynamics of outlet glaciers - Sentinel-1 A+B: apply the acqusition strategy to S1A and S1B - Icesheet wide Coverage: consecutive acquisitions (6 days repeat) - Margins: 6 tracks with 6 days repeat acquisitions Sentinel-2 Acquisition Strategy over Greenland needs to be discussed with ESA During Summer: need for continous monitoring of margins for ice velocity in synergy with SAR and mapping ice / snow reology, support calving fronts PSTG 5 th Session, 5-7 Oct Nagler & Rott 12

13 Greenland Sentinel-2 L1C data Data acquired during Comissioning Phase Sentinel-2 Band8 (10m) 16 Aug 2015 Sentinel-2 Band8 (10m) 8 Sept 2015 PSTG 5 th Session, 5-7 Oct Nagler & Rott 13

14 L1C (Terrain Rectified ) Data acquired in Commision Phase 16 Aug Sept 2015 Offset Tracking no cloud masking applied Stable Rock Analysis Sentinel-2 Ice Velocity Tracking - L1C Rectified Data set No Cloudmasking applied Clouds PSTG 5 th Session, 5-7 Oct Nagler & Rott 14

15 Sentinel-1 Coverage (30 Sept 2015) PSTG 5 th Session, 5-7 Oct Nagler & Rott 15

16 Pine Island Glacier, West Antarctica Average velocity 10/ / /1/2012 Icesheet Thomas Nagler 16

17 30 Sentinel 1 Ice velocity v h Product: 200 m Filchner / Ronne IS Gardner Inlet 16-17/1/2012 Icesheet Thomas Nagler 17 PSTG 5 th Session, 5-7 Oct Nagler & Rott 17

18 DEM Differencing and Mass Balance by InSAR Spatially detailed observations of surface elevation change by single pass SAR interferometry: TanDEM-X The change in glacier volume V over time t is converted to change of glacier mass (the net mass balance, B N ) : B N ( t) = V( t) Glacier ice: = 900 kg m -3 Effects of SAR signal penetration (position of scattering phase center, Z ) to be considered. Using repeat observations at same radar frequency and snow state (either dry or wet) or estimate penetration for given snow state and radar frequency (EM model and/or empirical data) Position of ( Z ) X-band: -1 m for refrozen firn -5 m for dry seasonal snow Depends on snow microstructure PSTG 5 th Session, 5-7 Oct Nagler V w [%] & Rott 18 Pen etration depth [m] = 0.4 gcm -3 Wet snow Z near surface

19 Elevation Change by TanDEM-X DEM Differencing Total Change (Basin 1 to 8) V = km 3 /yr M = Gt/yr Rott et al., GRL 2014 PSTG 5 th Session, 5-7 Oct Nagler & Rott 19

20 Sentinel-1 Acquisition Strategy for Antarctica Icesheet wide Coverage: - 1 Campaign (4 consecutive repeat acquisitions) per year, IW HH mode, Jun Sep - First campaign in 2015 started Monitoring Margins: - Currently: continuous acquisitions of Antarctic Peninsula and Amundsen SS - Extension to regions with main ice export and significant changes Proposed Coverage of margins to be continuously covered by S1 There is a high need for systematic Sentinel-2 acquisitions over Antarctica (Currently no Sentinel-2 acquisition over Antarctica planned) PSTG 5 th Session, 5-7 Oct Nagler & Rott 20