1. GOCE geoids and derived Mean Dynamic Topography in the Arctic Ocean Ole B. Andersen & Per Knudsen. DTU Space – Copenhagen, Denmark

2. GOCE 5th user workshop, UNESCO, Paris, France, November, 2014 2DTU Space, Technical University of Denmark Outline The Arctic Region. The GOCE Geoids in the Arctic (and problems) Altimetric MSS (and problems) Satellite derived MDT Summary

3. GOCE 5th user workshop, UNESCO, Paris, France, November, 2014 3DTU Space, Technical University of Denmark Study Area and problems Feb. Mar. Jul. 0 Fortunately Cryosat-2 provides altimetry Up to 88N.........

4. GOCE 5th user workshop, UNESCO, Paris, France, November, 2014 4DTU Space, Technical University of Denmark Satellite derived MDT The Mean Dynamic Topography is obtained through: 1.Subtracting a MSS and a GOCE geoid MDT = MSS – Geoid 2.Filtering to create consistent difference.

5. GOCE 5th user workshop, UNESCO, Paris, France, November, 2014 5DTU Space, Technical University of Denmark GOCE in the Arctic – Polar GAP....

6. GOCE 5th user workshop, UNESCO, Paris, France, November, 2014 6DTU Space, Technical University of Denmark Getting around the Polar Gap Normal equation scheme (EGM-DIR-5) contribution to the solution: reduced beforehand: GRACE Spherical harmonic degree 2602 130 180 GOCE SGG Txx + Tyy + Tzz + Txz LAGEOS 30 Spherical cap stabilizer 230 130175 300

7. GOCE 5th user workshop, UNESCO, Paris, France, November, 2014 7DTU Space, Technical University of Denmark GOCE GEOIDS Combinedd/o EGM082190 EIGEN C6-31949 Satellite Only DIR R3240 DIR R4260 DIR R5300 TIM R1224 TIM R5280 GOCO 3s250 DGM 1s250 ITG GOCE2s240 Ufilt Difference DIR R4 – DIR R5 Arctic > 66N>80N R4 – R5 (DIR)21 cm43 cm R4 – R5 (TIM)39 cm17 cm

8. GOCE 5th user workshop, UNESCO, Paris, France, November, 2014 8DTU Space, Technical University of Denmark GOCE Geoids diff (max degree) GOCE TIM R4 – GOCE DIR R4 GOCE TIM R5 – GOCE DIR R5 Arctic > 66N>80N R5 (DIR-TIM)39 cm72 cm Combined6 cm7 cm

9. GOCE 5th user workshop, UNESCO, Paris, France, November, 2014 9DTU Space, Technical University of Denmark ALTIMETRIC MSS CLS MSS01 CNES/CLS11

10. GOCE 5th user workshop, UNESCO, Paris, France, November, 2014 10DTU Space, Technical University of Denmark UCL and DTU MSS (complete) UCL04 (diff with 1Y of Cryosat-2) DTU 10

11. GOCE 5th user workshop, UNESCO, Paris, France, November, 2014 11DTU Space, Technical University of Denmark Tide In Arctic we Only have Sun syncronous satellites DAC

12. GOCE 5th user workshop, UNESCO, Paris, France, November, 2014 12DTU Space, Technical University of Denmark Very high number of data, but Seasonal Ice-coverage 100 % 0 % Typical error pattern follows number of data with decimeter error in The interior of the Arctic and sub decimeter error in Northern Atlantic. 20 Years (ERS1/ERS2/ENVISAT re-edited data coverage

13. GOCE 5th user workshop, UNESCO, Paris, France, November, 2014 13DTU Space, Technical University of Denmark Mean Dynamic Topography DTU13MDT DTU13MSS – EIGEN 6C-3 PIOMASGECCOTOPAZ

14. GOCE 5th user workshop, UNESCO, Paris, France, November, 2014 14DTU Space, Technical University of Denmark MDT from combined GOCE geoid models EGM08 EIGEN 6C-3 (DTU13) Gauss - filtering at 100 km 3

15. GOCE 5th user workshop, UNESCO, Paris, France, November, 2014 15DTU Space, Technical University of Denmark GOCE satellite only geoid models DIR R4 / R5 TIM R1 / R5 COCO 3S DGM 1S

16. GOCE 5th user workshop, UNESCO, Paris, France, November, 2014 16DTU Space, Technical University of Denmark Zonal differences Notice color scale doubles for every step....

17. GOCE 5th user workshop, UNESCO, Paris, France, November, 2014 17DTU Space, Technical University of Denmark MDT statistics (all to d/o=180). Signal (std) MeanMax (180) EGM080.1770.011.61 EIGEN C6-30.176-0.021.88 Satellite Only DIR R30.4940.024.41 DIR R40.3840.002.32 DIR R50.4110.002.29 TIM R10.7990.015.92 TIM R50.4670.002.22 GOCO 3s0.3030.031.59 DGM 1s0.3540.012.24 ITG GOCE20.7970.093.66

18. GOCE 5th user workshop, UNESCO, Paris, France, November, 2014 18DTU Space, Technical University of Denmark Conclusions Polar GAP is still a very vivid problem Spherical Cap regularisation is far from perfect.... EIGEN6C-3 and EGM2008 gives very similar MDT (same ArcGP data) Satellite only MDT exhibit ”star like pattern” Geoid differences seen down to 80 N. MSS are significantly less accurate Than at low latitude. 3 10cm/s 15cm/s 5-10cm/s Geostrophic currents from DTU13MDT Beaufort Gyre

19. GOCE 5th user workshop, UNESCO, Paris, France, November, 2014 19DTU Space, Technical University of Denmark Thank You