a global estimate of mountain glacier volume and mass
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1 [email protected] A Global Estimate of Mountain Glacier Volume and Mass Change and …. Neue Perspektiven der Erdbeobachtung 13.11.2019
A Global Estimate of Mountain Glacier Volume and Mass Change and its Contribution to Sea Level Rise between 60°N and 56°S
T Seehaus, C Sommer, P Malz, D Farías, M Braun
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2 [email protected] A Global Estimate of Mountain Glacier Volume and Mass Change and …. Neue Perspektiven der Erdbeobachtung 13.11.2019
Sea level change as measured from satellite
Currently about almost a third comes from glaciers and ice caps
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3 [email protected] A Global Estimate of Mountain Glacier Volume and Mass Change and …. Neue Perspektiven der Erdbeobachtung 13.11.2019
Sea level change and ice mass contributions
Globally ~215 000 glaciers and ice caps • 158 ± 41 * 10³ km³ (2019), ~50 -130 * 10³ km³ (IPCC 2013) • 0.32 ± 0.08 m sea level contribution (Farinotti et al. 2019),
0.41 m(IPCC 2013) • Only 2% of the glaciers
have so far any in-situ ice thickness measurement
Farinotti et al. (2019), NGEO
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4 [email protected] A Global Estimate of Mountain Glacier Volume and Mass Change and …. Neue Perspektiven der Erdbeobachtung 13.11.2019
Gardner et al. 2013
Motivation: Mass budget worldwide…
Zemp et al. 2019
Mass budgets of glaciers worldwide so far
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5 [email protected] A Global Estimate of Mountain Glacier Volume and Mass Change and …. Neue Perspektiven der Erdbeobachtung 13.11.2019
DEM differencing to derive dh/dt
Methods: Derive dh/dt from TanDEM-X
SRTM:
C-band bistatic SAR
TanDEM-X:
X-band bistatic SAR
Image: DLR
Image: NASA
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6 [email protected] A Global Estimate of Mountain Glacier Volume and Mass Change and …. Neue Perspektiven der Erdbeobachtung 13.11.2019
Methods: Derive dh/dt from input data
SRTM input:
DEM-product Version 3.0
Res: 1 arc sec
t0 = 2000-16-02
• Create projected, non void filled mosaics of 1x1° tiles
dh/dt dataset
TanDEM-X - SRTM output:
Projected 30x30 m pixel maps of dh/dt:
Elev.(TDX) – Elev.(SRTM)
t1 – t0
TanDEM-X input:
SLC-products (archive)
Res: processed to reference (SRTM)
t1 = 2011/12/13
• Select scene pairs (>4000) • InSAR process DEMs • Adjust and mosaic
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7 [email protected] A Global Estimate of Mountain Glacier Volume and Mass Change and …. Neue Perspektiven der Erdbeobachtung 13.11.2019
TanDEM-X DEM-processing
Differential InSAR processing: → Interferogram calculation with SRTM as reference model
Deramping and further corrections: → Minimizing systematic errors for each DEM strip (Nuth & Kääb 2011, Malz et al. 2018)
From TanDEM-X to elevation change datasets
Mosaicing, differencing, masking and error assessment → Combining data takes to a subregional result
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8 [email protected] A Global Estimate of Mountain Glacier Volume and Mass Change and …. Neue Perspektiven der Erdbeobachtung 13.11.2019
Mass balance by geodetic method in the constraints of SRTM orbits: <60°N and >56°S
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DEM differencing:
TanDEM-X SRTM
dh/dt dM/dt
Our approach:
this study
Area [km²]
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Total: ~175,000
Motivation: mb by one single method
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9 [email protected] A Global Estimate of Mountain Glacier Volume and Mass Change and …. Neue Perspektiven der Erdbeobachtung 13.11.2019
Our results: Elevation change
Aggregated mean dh/dt per 1x1° lat/lon – area scaled center points
Results: Gridded elevation change overview
DEM differencing:
TanDEM-X SRTM
dh/dt dM/dt
Aggregated results to enhance overview
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10 [email protected] A Global Estimate of Mountain Glacier Volume and Mass Change and …. Neue Perspektiven der Erdbeobachtung 13.11.2019
Regionalized change results: Southern Patagonia Icefield
dh/dt 2000-2012
Northern Patagonia Icefield dh/dt 2000-2012
Results: South America - elevation change
• Patagonia (8 & 9) shows the most extreme negative change rates
• Dessert (5) and Central Andes (6) as well as Lake District (7) slightly negative to balanced
• Tropical Andes (1-4) heterogenous
Specific mass balance (m.w.e./a)
Mass Balance South America (Braun et al 2019): 19.4 ± 0.6 Gt a-1
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13 [email protected] A Global Estimate of Mountain Glacier Volume and Mass Change and …. Neue Perspektiven der Erdbeobachtung 13.11.2019
Regionalized change results:
• Himalaya shows
clear depletion
• Minima in Spiti Lahaul and Nyenquentangla range regions
• Hindu Kush, Outer Tien Shan & E Tibetan Plateau show slightly negative changes
Results: High mountain Asia - elevation change
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14 [email protected] A Global Estimate of Mountain Glacier Volume and Mass Change and …. Neue Perspektiven der Erdbeobachtung 13.11.2019
Regionalized change results:
• Central Tien Shan,
Pamir, W Karakoram more or less balanced
• Kunlun Shan and W Tibetan Plateau gain height
• Large accumulation areas with positve change rates
Results: High mountain Asia - elevation change
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15 [email protected] A Global Estimate of Mountain Glacier Volume and Mass Change and …. Neue Perspektiven der Erdbeobachtung 13.11.2019
Regionalized change results:
• Central Tien Shan,
Pamir, W Karakoram more or less balanced
• Kunlun Shan and W Tibetean Plateau gain height
• Large accumulation areas with positve change rates
Results: High mountain Asia - elevation change
Karakoram:
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16 [email protected] A Global Estimate of Mountain Glacier Volume and Mass Change and …. Neue Perspektiven der Erdbeobachtung 13.11.2019
Regionalized change results:
• Central Tien Shan,
Pamir, W Karakoram more or less balanced
• Kunlun Shan and W Tibetean Plateau gain height
• Large areas with positve change rates
Results: High mountain Asia - elevation change
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17 [email protected] A Global Estimate of Mountain Glacier Volume and Mass Change and …. Neue Perspektiven der Erdbeobachtung 13.11.2019
Regionalized change results:
• Central Tien Shan,
Pamir, W Karakoram more or less balanced
• Kunlun Shan and W Tibetean Plateau gain height
• Large accumulation areas with positve change rates
Results: High mountain Asia - elevation change
Kunlun:
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18 [email protected] A Global Estimate of Mountain Glacier Volume and Mass Change and …. Neue Perspektiven der Erdbeobachtung 13.11.2019
Regionalized mass balance:
Results*: High mountain Asia - mass balance
negative mb
positive /neutral mb
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19 [email protected] A Global Estimate of Mountain Glacier Volume and Mass Change and …. Neue Perspektiven der Erdbeobachtung 13.11.2019
Regionalized mass balance:
Results*: High mountain Asia - mass balance
• Positive elevation change signal needs further investigation : influence of climate vs. weather vs. penetration differences vs. SRTM related biases
• Standard processing with constant density of 900 km m-3 not yet adjusted for large gaining accumulation areas
negative mb
positive /neutral mb
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20 [email protected] A Global Estimate of Mountain Glacier Volume and Mass Change and …. Neue Perspektiven der Erdbeobachtung 13.11.2019
Results: North America - elevation change
Overview:
North America West
Stikine Icefield dh/dt 2000-2012
Juneau Icefield dh/dt 2000-2012
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21 [email protected] A Global Estimate of Mountain Glacier Volume and Mass Change and …. Neue Perspektiven der Erdbeobachtung 13.11.2019
Results: North America – hypsometric analysis
Stikine Icefield dh/dt 2000-2012
Juneau Icefield dh/dt 2000-2012
fields
Berthier et al. 2018 (ASTER)
Our results
Hypsometric distribution of elevation change and glacier area
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22 [email protected] A Global Estimate of Mountain Glacier Volume and Mass Change and …. Neue Perspektiven der Erdbeobachtung 13.11.2019
-44.95 ± 1.3 Gt a-1 mass balance world wide in SRTM constraints (174,740 km²)
10,000
Our preliminary results: Mass balance (2000-2011/15)
inte
rpo
late
d
me
asu
red
Area [km²]
Results: „Global“ mass balance
-20
Mass balance [Gt a-1]
-1
-10 1+2
3
16
17
2
11
7 9
12 13-15
10
19 18
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23 [email protected] A Global Estimate of Mountain Glacier Volume and Mass Change and …. Neue Perspektiven der Erdbeobachtung 13.11.2019
Conclusions:
• Mass balance (2000-2011/17) by the presented geodetic method results preliminarily to a total of - 44.95 ± 1.3 Gt a-1 on 174,740 km²
• Comparability of southern and northern hemispheric datasets require some assumptions on glacier surface conditions and penetration depth.
• Processing chain is almost ready for a second real global approach – i.e. the extension of our analysis to the Arctic – depend on a second global acquisition with TanDEM-X or a comparable, compatible X-Band mission Problem: data is not released
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24 [email protected] A Global Estimate of Mountain Glacier Volume and Mass Change and …. Neue Perspektiven der Erdbeobachtung 13.11.2019
Thank you for your attention!
Acknowledgements:
TanDEM-X satellite data was kindly provided under DLR AO XTI_GLAC0264
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25 [email protected] A Global Estimate of Mountain Glacier Volume and Mass Change and …. Neue Perspektiven der Erdbeobachtung 13.11.2019
Comparison
C-Band SRTM TanDEM-X 90m:
• SRTM positively
biased on central N to S axis of Tibetan Plateau
• Steep ranges in W and N with slight positve tendency
• Signals not overruled by artefacts (moasic, geoid correction, acquisition geometry)
Results evaluating elevation change
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26 [email protected] A Global Estimate of Mountain Glacier Volume and Mass Change and …. Neue Perspektiven der Erdbeobachtung 13.11.2019
Comparison
C-Band SRTM
X-Band SRTM:
• Pattern is not reliably equal to TanDEM-X DEM comparison
• Gaps a decicive positions (accumulation areas)
• Mosaicing artefacts predominant
Results evaluating elevation change
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27 [email protected] A Global Estimate of Mountain Glacier Volume and Mass Change and …. Neue Perspektiven der Erdbeobachtung 13.11.2019
Results: North america – hypsometric analysis
Stikine Icefield dh/dt 2000-2012
Juneau Icefield dh/dt 2000-2012
fields
Berthier et al.
2018 (ASTER)
Our results
• Results in accordance with published ones
• SRTM gaps negliglable
• No systematic bias for accumulation area in North America
Hypsometric distribution of elevation change and glacier area