SSH retrieval in the ice covered Arctic Ocean: from waveform classification to regional sea level maps

Transcription

1 ESA Climate Change Initiative SSH retrieval in the ice covered Arctic Ocean: from waveform classification to regional sea level maps CLS LEGOS PML

2 Arctic SIE status 2 nd lowest on record with km² Reached on september 10th

3 PROCESSING Sea Level CCI Phase II AR#3 and Final Meeting February th 2017

4 Processing strategy Waveform classification, Dedicated retracking, Geophysical corrections, Data editing, 2016 Consistency with GMSL Gridding, 2016 Sea Level CCI Phase II AR#3 and Final Meeting February th 2017

5 Waveform selection & retracking Brownian (open ocean) and specular (leads) returns selected, One adaptive retracker to rule them all, No need for a open ocean/lead bias

6 Mean SLA (m) Sea Level CCI Phase II AR#3 and Final Meeting February th 2017 Data editing MQE and backscatter, hooking points through backscatter variations, Temporal editing based on local signal variance, Decreasing hooking flag severity

7 SLA estimation Geophysical corrections based on models as much as possible, Missions referenced to the global MSL between 50 and 66 with LSR 2016

8 Final SARAL product Daily grids, Not independent (30 day avg), On 2 by 1 cells, Only SARAL and Envisat at the moment, CryoSat-2 expected in the near future, Future: ERS, Sentinel-3

9 REGIONAL AVERAGES Sea Level CCI Phase II AR#3 and Final Meeting February th 2017

10 Arctic sea level variability Variability in agreement with DTU, Trends are slightly different (but uncertainties are likely high)

11 Arctic sea level variability Variability in agreement with DTU, Trends are slightly different (but uncertainties are likely high)

12 Arctic sea level variability Variability in agreement with DTU, Trends are slightly different (but uncertainties are likely high)

13 REGIONAL DISTRIBUTION Sea Level CCI Phase II AR#3 and Final Meeting February th 2017

14 Arctic sea level variability Variability trapped at the coast for CLS/PML, homogeneous for DTU Beaufort gyre visible in Envisat record,

15 Comparing variability levels to the few tide gauges available Comparison sample is (very) small, Slightly better agreement than with DTU dataset, is it significant?

16 Seasonal signal Amplitude Phase (month of max) Sea Level CCI Phase II AR#3 and Final Meeting February th 2017

17 Trends Consistent trends distribution, But slightly larger amplitudes Sea Level CCI Phase II AR#3 and Final Meeting February th 2017

18 Regional SL budget From Carret et al. (submitted), Comparisons between altimetry minus steric and GRACE ocean mass trends

19 CONCLUSION & OUTLOOK Sea Level CCI Phase II AR#3 and Final Meeting February th 2017

20 Conclusion Based on waveform classification & new retracking algorithm Improvements in 2016 : Improved Hooking Flag Consistency with with GMSL record (no extra referencing effort needed) First validation results suggest a good performance, More geophysical validation in Carret et al., submitted Freely available upon request to info-sealevel@esa-sealevel-cci.org, Sea Level CCI Phase II AR#3 and Final Meeting February th 2017

21 Outlook To continue to improve sea-level estimation from high rate altimeter measurements, thanks to adapted retracking algorithms, better altimeter corrections (ocean tide, mean sea-surface, dynamic atmospheric corrections, etc..), To provide regional sea-level products dedicated to high latitude areas covering all the altimeter period from 1992 onwards and based on ERS- 1, ERS-2, Envisat, Cryosat, SARAL-Altika and Sentinel-3 missions. To improve these products with new dedicated algorithms such as dedicated editing algorithms, mapping algorithms To improve the sea-level seamless transition with the global sea level ECVs products