# Temporal Variations in Ice Thickness of the Shirase Glacier Derived from Cryosat-2/SIRAL Data

^{1}

^{2}

^{*}

## Abstract

**:**

## 1. Introduction

^{−1}[6]. As in West Antarctica, it was observed that the basal melting beneath the tongue of the Shirase Glacier caused an inflow of southward-flowing warm water from offshore [7], but the interannual variability of the inflow of warm water needs to be considered. Therefore, it is important to accurately measure the ice thickness of the glacier in order to continuously monitor the trend of the ice mass balance.

^{−1}[10]; furthermore, the flow velocity at the grounding line of the Shirase Glacier, which was 2.3 km a

^{−1}, made it one of the fastest flowing glaciers, and extremely fast compared to most other known glaciers, since the mean flow velocity of the 9 glaciers in East Antarctica is 1.0 km a

^{−1}[11]. The application of the offset tracking method to intensity images derived from SAR has been shown to be effective for fast-flowing glaciers such as the Shirase Glacier (e.g., [12]), and the flow velocity at the grounding line has shown no significant changes in the last 24 years [13], while interannual variation in ice thickness remains insufficiently studied.

## 2. Materials and Methods

#### 2.1. Estimation of the Area of the Shirase Glacier

#### 2.2. CryoSat-2/SIRAL Data

^{−3}and 1.47–j0.0001 [31], respectively. Since the penetration depth was one order larger than the measured snow depth, we considered the snow on the glacier to make a negligible contribution to the backscatter of CryoSat-2/SIRAL. Therefore, we did not apply backscatter correction to the CryoSat-2/SIRAL data used in this study.

#### 2.3. ALOS World 3D Data

#### 2.4. Control Point Survey Results

#### 2.5. Conversion of CryoSat-2/SIRAL Data into Ice Thickness

## 3. Results

#### 3.1. Comparison of CryoSat-2 Height with AW3D30 DSM

#### 3.2. Estimate of Ice Thickness

## 4. Discussion

#### 4.1. Decline of Ice Thickness with Distance from Grounding Line

^{−1}[13]. This is comparable to the decline in estimated ice thickness obtained using the ice radar, which was 7–16 m, resulting from basal melting, located approximately 20 km downstream from the grounding line [7]; however, it is possible that there are other factors at play, as discussed in Section 4.2. Meanwhile, an annual ${H}_{dec}$ of 0.1 m was obtained in $D$ ≥ 35 km, suggesting that the contribution of basal melting to the difference in ice thickness was minimal.

#### 4.2. Fluctuation of Ice Thickness with the Breaking Away of Glacier and Landfast Ice

^{−1}at the grounding line of Shirase Glacier [13]. In the profile at 30 km in Figure 8, the ice thickness in 2012 (14 years after 1998) was 330.0 m, while the mean thickness for 2012–2020 was 356.5 m; therefore, the difference from the mean was 26.5 m. Hence, the profile at 30 km downstream in 2012 showed a lesser value than in other years. The change in ice thickness 30 km downstream from the grounding line in 2012 should be compared with that at 25 km downstream from the grounding line in 2010 (as there was less than a 5 km advance between 2010 and 2012); however, the ice thickness in 2010 was obtained in this study due to insufficient stacking for the analysis. Consequently, the ice thickness at 25 km downstream from the grounding line in 2011 was verified, and the profile at 25 km in 2011 presented in Figure 8 was the lesser, at 426.4 m (where the mean for 2012–2020 was 449.3 m). This was attributed to the acceleration in the glacier flow associated with the retreat of the terminus of the Shirase Glacier in 1998 [12]. Similarly, the ice thickness in 2005 was not determined, but the glacier would have advanced approximately 30 km in 12 years, and the profile at 30 km in 2017, presented in Figure 8, can be regarded as indicating the change 12 years after 2005. In this figure, the profile at 30 km in 2017 was 314.3 m, corresponding to a difference from the mean of 42.2 m and showing a lesser value compared to other years. The ice thickness 30 km downstream from the grounding line in 2017 was compared with that 25 km downstream from the grounding line in 2015. The profile 25 km downstream in 2015, presented in Figure 8, was 451.5 m, which was the smallest value between 2013 and 2016. This was attributed to the breaking up and flowing out of the southernmost landfast ice into Lützow-Holm Bay, which surrounds the terminus of the Shirase Glacier, in 2005 [33].

## 5. Conclusions

## Supplementary Materials

## Author Contributions

## Funding

## Data Availability Statement

## Acknowledgments

## Conflicts of Interest

## Appendix A

Date/Orbit | Date/Orbit | Date/Orbit | Date/Orbit |
---|---|---|---|

06 Jan 2011/Descending | 11 Jan 2011/Ascending | 04 Feb 2011/Descending | 07 Feb 2011/Ascending |

02 Mar 2011/Descending | 08 Mar 2011/Ascending | 31 Mar 2011/Descending | 06 Apr 2011/Ascending |

29 Apr 2011/Descending | 05 May 2011/Ascending | 26 May 2011/Descending | 24 Jun 2011/Descending |

30 Jun 2011/Ascending | 23 Jul 2011/Descending | 29 Jul 2011/Ascending | 19 Aug 2011/Descending |

21 Aug 2011/Descending | 25 Aug 2011/Ascending | 15 Sep 2011/Descending | 17 Sep 2011/Descending |

23 Sep 2011/Ascending | 16 Oct 2011/Descending | 21 Oct 2011/Ascending | 12 Nov 2011/Descending |

14 Nov 2011/Descending | 17 Nov 2011/Ascending | 11 Dec 2011/Descending | 16 Dec 2011/Ascending |

09 Jan 2012/Descending | 14 Jan 2012/Ascending | 07 Feb 2012/Descending | 10 Feb 2012/Ascending |

05 Mar 2012/Descending | 07 Mar 2012/Descending | 10 Mar 2012/Ascending | 03 Apr 2012/Descending |

08 Apr 2012/Ascending | 02 May 2012/Descending | 05 May 2012/Ascending | 07 May 2012/Ascending |

29 May 2012/Descending | 31 May 2012/Descending | 03 Jun 2012/Ascending | 26 Jun 2012/Descending |

02 Jul 2012/Ascending | 25 Jul 2012/Descending | 31 Jul 2012/Ascending | 21 Aug 2012/Descending |

23 Aug 2012/Descending | 27 Aug 2012/Ascending | 19 Sep 2012/Descending | 25 Sep 2012/Ascending |

18 Oct 2012/Descending | 24 Oct 2012/Ascending | 14 Nov 2012/Descending | 16 Nov 2012/Descending |

20 Nov 2012/Ascending | 22 Nov 2012/Ascending | 13 Dec 2012/Descending | 19 Dec 2012/Ascending |

11 Jan 2013/Descending | 17 Jan 2013/Ascending | 07 Feb 2013/Descending | 09 Feb 2013/Descending |

13 Feb 2013/Ascending | 08 Mar 2013/Descending | 13 Mar 2013/Ascending | 06 Apr 2013/Descending |

11 Apr 2013/Ascending | 05 May 2013/Descending | 08 May 2013/Ascending | 01 Jun 2013/Descending |

06 Jun 2013/Descending | 30 Jun 2013/Descending | 05 Jul 2013/Ascending | 29 Jul 2013/Descending |

03 Aug 2013/Ascending | 25 Aug 2013/Descending | 27 Aug 2013/Descending | 30 Aug 2013/Ascending |

23 Sep 2013/Descending | 28 Sep 2013/Ascending | 02 Oct 2013/Ascending | 21 Oct 2013/Descending |

27 Oct 2013/Ascending | 17 Nov 2013/Descending | 19 Nov 2013/Descending | 23 Nov 2013/Ascending |

16 Dec 2013/Descending | 22 Dec 2013/Ascending | 14 Jan 2014/Descending | 20 Jan 2014/Ascending |

10 Feb 2014/Descending | 12 Feb 2014/Descending | 16 Feb 2014/Ascending | 11 Mar 2014/Descending |

15 Mar 2014/Ascending | 17 Mar 2014/Ascending | 09 Apr 2014/Descending | 15 Apr 2014/Ascending |

08 May 2014/Descending | 04 Jun 2014/Descending | 06 Jun 2014/Descending | 08 Jun 2014/Ascending |

10 Jun 2014/Ascending | 12 Jun 2014/Ascending | 03 Jul 2014/Descending | 08 Jul 2014/Ascending |

01 Aug 2014/Descending | 06 Aug 2014/Ascending | 28 Aug 2014/Descending | 30 Aug 2014/Descending |

02 Sep 2014/Ascending | 22 Sep 2014/Descending | 26 Sep 2014/Descending | 01 Oct 2014/Ascending |

25 Oct 2014/Descending | 30 Oct 2014/Ascending | 21 Nov 2014/Descending | 23 Nov 2014/Descending |

26 Nov 2014/Ascending | 20 Dec 2014/Descending | 25 Dec 2014/Ascending | 27 Dec 2014/Ascending |

18 Jan 2015/Descending | 20 Jan 2015/Descending | 23 Jan 2015/Ascending | 15 Feb 2015/Descending |

19 Feb 2015/Ascending | 14 Mar 2015/Descending | 20 Mar 2015/Ascending | 12 Apr 2015/Descending |

18 Apr 2015/Ascending | 11 May 2015/Descending | 17 May 2015/Ascending | 07 Jun 2015/Descending |

13 Jun 2015/Ascending | 06 Jul 2015/Descending | 12 Jul 2015/Ascending | 04 Aug 2015/Descending |

10 Aug 2015/Ascending | 31 Aug 2015/Descending | 02 Sep 2015/Descending | 06 Sep 2015/Ascending |

29 Sep 2015/Descending | 05 Oct 2015/Ascending | 28 Oct 2015/Descending | 02 Nov 2015/Ascending |

22 Nov 2015/Descending | 24 Nov 2015/Descending | 26 Nov 2015/Descending | 29 Nov 2015/Ascending |

30 Nov 2015/Descending | 23 Dec 2015/Descending | 28 Dec 2015/Ascending | 21 Jan 2016/Descending |

26 Jan 2016/Ascending | 19 Feb 2016/Descending | 22 Feb 2016/Ascending | 17 Mar 2016/Descending |

19 Mar 2016/Descending | 22 Mar 2016/Ascending | 15 Apr 2016/Descending | 20 Apr 2016/Ascending |

14 May 2016/Descending | 19 May 2016/Ascending | 09 Jun 2016/Descending | 11 Jun 2016/Descending |

15 Jun 2016/Ascending | 08 Jul 2016/Descending | 14 Jul 2016/Ascending | 06 Aug 2016/Descending |

12 Aug 2016/Ascending | 29 Aug 2016/Descending | 02 Sep 2016/Descending | 04 Sep 2016/Descending |

08 Sep 2016/Ascending | 01 Oct 2016/Descending | 07 Oct 2016/Ascending | 30 Oct 2016/Descending |

05 Nov 2016/Ascending | 26 Nov 2016/Descending | 28 Nov 2016/Descending | 02 Dec 2016/Ascending |

25 Dec 2016/Descending | 31 Dec 2016/Ascending | 23 Jan 2017/Descending | 25 Jan 2017/Descending |

29 Jan 2017/Ascending | 21 Feb 2017/Descending | 24 Feb 2017/Ascending | 20 Mar 2017/Descending |

25 Mar 2017/Ascending | 18 Apr 2017/Descending | 23 Apr 2017/Ascending | 17 May 2017/Descending |

20 May 2017/Ascending | 22 May 2017/Ascending | 13 Jun 2017/Descending | 18 Jun 2017/Ascending |

12 Jul 2017/Descending | 17 Jul 2017/Ascending | 10 Aug 2017/Descending | 15 Aug 2017/Ascending |

06 Sep 2017/Descending | 08 Sep 2017/Descending | 11 Sep 2017/Ascending | 04 Oct 2017/Descending |

10 Oct 2017/Ascending | 31 Oct 2017/Descending | 02 Nov 2017/Descending | 08 Nov 2017/Ascending |

29 Nov 2017/Descending | 01 Dec 2017/Descending | 03 Dec 2017/Ascending | 05 Dec 2017/Ascending |

28 Dec 2017/Descending | 03 Jan 2018/Ascending | 26 Jan 2018/Descending | 01 Feb 2018/Ascending |

24 Feb 2018/Descending | 28 Feb 2018/Ascending | 29 Mar 2018/Ascending | 21 Apr 2018/Descending |

27 Apr 2018/Ascending | 20 May 2018/Descending | 24 May 2018/Ascending | 16 Jun 2018/Descending |

18 Jun 2018/Descending | 21 Jun 2018/Ascending | 15 Jul 2018/Descending | 18 Jul 2018/Ascending |

20 Jul 2018/Ascending | 13 Aug 2018/Descending | 18 Aug 2018/Ascending | 09 Sep 2018/Descending |

12 Sep 2018/Ascending | 14 Sep 2018/Ascending | 08 Oct 2018/Descending | 11 Oct 2018/Ascending |

13 Oct 2018/Ascending | 04 Nov 2018/Descending | 06 Nov 2018/Descending | 11 Nov 2018/Ascending |

03 Dec 2018/Descending | 05 Dec 2018/Descending | 08 Dec 2018/Ascending | 01 Jan 2019/Descending |

06 Jan 2019/Ascending | 29 Jan 2019/Descending | 04 Feb 2019/Ascending | 27 Feb 2019/Descending |

03 Mar 2019/Ascending | 26 Mar 2019/Descending | 01 Apr 2019/Ascending | 05 Apr 2019/Ascending |

24 Apr 2019/Descending | 30 Apr 2019/Ascending | 23 May 2019/Descending | 29 May 2019/Ascending |

19 Jun 2019/Descending | 25 Jun 2019/Ascending | 18 Jul 2019/Descending | 24 Jul 2019/Ascending |

16 Aug 2019/Descending | 22 Aug 2019/Ascending | 12 Sep 2019/Descending | 14 Sep 2019/Descending |

18 Sep 2019/Ascending | 20 Sep 2019/Ascending | 09 Oct 2019/Descending | 11 Oct 2019/Descending |

14 Oct 2019/Ascending | 16 Oct 2019/Ascending | 09 Nov 2019/Descending | 14 Nov 2019/Ascending |

06 Dec 2019/Descending | 08 Dec 2019/Descending | 11 Dec 2019/Ascending | 04 Jan 2020/Descending |

09 Jan 2020/Ascending | 02 Feb 2020/Descending | 07 Feb 2020/Ascending | 02 Mar 2020/Descending |

05 Mar 2020/Ascending | 27 Mar 2020/Descending | 29 Mar 2020/Descending | 31 Mar 2020/Descending |

03 Apr 2020/Ascending | 27 Apr 2020/Descending | 02 May 2020/Ascending | 25 May 2020/Descending |

29 May 2020/Descending | 31 May 2020/Ascending | 21 Jun 2020/Descending | 23 Jun 2020/Descending |

25 Jun 2020/Ascending | 27 Jun 2020/Ascending | 20 Jul 2020/Descending | 22 Jul 2020/Descending |

26 Jul 2020/Ascending | 12 Aug 2020/Descending | 14 Aug 2020/Descending | 18 Aug 2020/Descending |

08 Sep 2020/Descending | 12 Sep 2020/Ascending | 14 Sep 2020/Ascending | 03 Oct 2020/Descending |

07 Oct 2020/Ascending | 24 Oct 2020/Descending | 26 Oct 2020/Descending | 01 Nov 2020/Ascending |

20 Nov 2020/Descending | 26 Nov 2020/Ascending | 15 Dec 2020/Descending |

Date/Orbit | Date/Orbit | Date/Orbit | Date/Orbit |
---|---|---|---|

31 Mar 2011/Descending | 04 Apr 2011/Ascending | 26 May 2011/Descending | 19 Aug 2011/Descending |

12 Nov 2011/Descending | 12 Jan 2012/Ascending | 05 Mar 2012/Descending | 29 May 2012/Descending |

30 Jun 2012/Ascending | 23 Sep 2012/Ascending | 09 Apr 2013/Ascending | 01 Jun 2013/Descending |

30 Jun 2013/Descending | 25 Aug 2013/Descending | 04 Jun 2014/Descending | 03 Jul 2014/Descending |

06 Jul 2014/Ascending | 28 Aug 2014/Descending | 21 Nov 2014/Descending | 12 Apr 2015/Descending |

16 Apr 2015/Ascending | 13 Jun 2015/Ascending | 06 Jul 2015/Descending | 10 Jul 2015/Ascending |

31 Aug 2015/Descending | 03 Oct 2015/Ascending | 31 Oct 2015/Ascending | 24 Nov 2015/Descending |

22 Feb 2016/Ascending | 18 Apr 2016/Ascending | 09 Jun 2016/Descending | 08 Jul 2016/Descending |

12 Jul 2016/Ascending | 02 Sep 2016/Descending | 05 Oct 2016/Ascending | 20 Mar 2017/Descending |

13 Jun 2017/Descending | 12 Jul 2017/Descending | 06 Sep 2017/Descending | 08 Oct 2017/Ascending |

25 Apr 2018/Ascending | 18 Jul 2018/Ascending | 09 Sep 2018/Descending | 03 Dec 2018/Descending |

02 Feb 2019/Ascending | 28 Apr 2019/Ascending | 19 Jun 2019/Descending | 18 Jul 2019/Descending |

22 Jul 2019/Ascending | 12 Sep 2019/Descending | 11 Dec 2019/Ascending | 05 Feb 2020/Ascending |

30 Apr 2020/Ascending | 23 May 2020/Descending | 21 Jun 2020/Descending | 27 Jun 2020/Ascending |

24 Jul 2020/Ascending | 26 Oct 2020/Descending | 30 Oct 2020/Ascending |

## References

- Fretwell, P.; Pritchard, H.D.; Vaughan, D.G.; Bamber, J.L.; Barrand, N.E.; Bell, R.; Bianchi, C.; Bingham, R.G.; Blankenship, D.D.; Casassa, G.; et al. BEDMAP2: Improved ice bed, surface and thickness datasets for Antarctica. Cryosphere
**2013**, 7, 375–393. [Google Scholar] [CrossRef] [Green Version] - Rignot, E.; Jacobs, S.; Mouginot, J.; Scheuchl, B. Ice-shelf melting around Antarctica. Science
**2013**, 341, 266–270. [Google Scholar] [CrossRef] [Green Version] - Rignot, E.; Vaughan, D.; Schmeltz, M.; Dupont, T.; Macayeal, D. Acceleration of Pine Island and Thwaites Glaciers, West Antarctica. Ann. Glaciol.
**2002**, 34, 189–194. [Google Scholar] [CrossRef] [Green Version] - Shepherd, A.; Ivins, E.R.; Geruo, A.; Barletta, V.R.; Bentley, M.J.; Bettadpur, S.; Briggs, K.H.; Bromwich, D.H.; Forsberg, R.; Galin, N.; et al. A Reconciled Estimate of Ice-Sheet Mass Balance. Science
**2012**, 338, 1183–1189. [Google Scholar] [CrossRef] [Green Version] - Rignot, E.; Bamber, J.L.; van den Broeke, M.R.; Davis, C.; Li, Y.; van de Berg, W.J.; van Meijgaard, E. Recent Antarctic ice mass loss from radar interferometry and regional climate modelling. Nat. Geosci.
**2008**, 1, 106–110. [Google Scholar] [CrossRef] [Green Version] - Nakamura, K.; Yamanokuchi, T.; Doi, K.; Shibuya, K. Net mass balance calculations for the Shirase Drainage Basin, east Antarctica, using the mass budget method. Polar Sci.
**2016**, 10, 111–122. [Google Scholar] [CrossRef] - Hirano, D.; Tamura, T.; Kusahara, K.; Ohshima, K.I.; Nicholls, K.W.; Ueno, S.; Simizu, D.; Ono, K.; Fujii, M.; Nogi, Y.; et al. Strong ice-ocean interaction beneath Shirase Glacier Tongue in East Antarctica. Nat. Commun.
**2020**, 11, 4221. [Google Scholar] [CrossRef] - Nakawo, M.; Ageta, Y.; Yoshimura, A. Discharge of ice across Soya Coast. Mem. Nat. Inst. Polar Res. Spec. Issue
**1978**, 7, 235–244. [Google Scholar] - Fujii, Y. Aerophotographic interpretation of surface features and estimation of ice discharge at the outlet of the Shirase drainage basin Antarctica. Antarct. Rec.
**1981**, 72, 1–15. [Google Scholar] [CrossRef] - Pattyn, F.; Derauw, D. Ice-dynamic conditions of Shirase Glacier, Antarctica, inferred from ERS SAR interferometry. J. Glaciol.
**2002**, 48, 559–565. [Google Scholar] [CrossRef] [Green Version] - Rignot, E. Mass balance of East Antarctic glaciers and ice shelves from satellite data. Ann. Glaciol.
**2002**, 34, 217–227. [Google Scholar] [CrossRef] [Green Version] - Nakamura, K.; Doi, K.; Shibuya, K. Estimation of seasonal changes in the flow of Shirase Glacier using JERS-1/SAR image correlation. Polar Sci.
**2007**, 1, 73–83. [Google Scholar] [CrossRef] [Green Version] - Nakamura, K.; Aoki, S.; Yamanokuchi, T.; Tamura, T.; Doi, K. Validation for Ice Flow Velocity Variations of Shirase Glacier Derived From PALSAR-2 Offset Tracking. IEEE J. Sel. Top. App. Earth Obs. Remote Sens.
**2022**, 5, 3269–3281. [Google Scholar] [CrossRef] - Griggs, J.; Bamber, J. Antarctic ice-shelf thickness from satellite radar altimetry. J. Glaciol.
**2011**, 57, 485–498. [Google Scholar] [CrossRef] [Green Version] - Laxon, S.W.; Giles, K.A.; Ridout, A.L.; Wingham, D.J.; Willatt, R.; Cullen, R.; Kwok, R.; Schweiger, A.; Zhang, J.; Haas, C.; et al. CryoSat-2 estimates of Arctic sea ice thickness and volume. Geophys. Res. Lett.
**2013**, 40, 732–737. [Google Scholar] [CrossRef] [Green Version] - McMillan, M.; Shepherd, A.; Sundal, A.; Briggs, K.; Muir, A.; Ridout, A.; Hogg, A.; Wingham, D. Increased ice losses from Antarctica detected by CryoSat-2. Geophys. Res. Lett.
**2014**, 41, 3899–3905. [Google Scholar] [CrossRef] - Chuter, S.J.; Bamber, J.L. Antarctic ice shelf thickness from CryoSat-2 radar altimetry. Geophys. Res. Lett.
**2015**, 42, 10721–10729. [Google Scholar] [CrossRef] [Green Version] - Naruse, R. Surface flow and strain of the ice sheet measured by a triangulation chain in Mizuho Plateau. Mem. Nat. Inst. Polar Res. Spec. Issue
**1978**, 7, 198–226. [Google Scholar] - Mae, S.; Naruse, R. Possible causes of ice sheet thinning in the Mizuho Plateau. Nature
**1978**, 273, 291–292. [Google Scholar] [CrossRef] - Fujii, Y.; Kusunoki, K. The role of sublimation and condensation in the formation of ice sheet surface at Mizuho Plateau. Antarct. J. Geophys. Res.
**1982**, 78, 4293–4300. [Google Scholar] [CrossRef] - Yamanokuchi, T.; Doi, K.; Shibuya, K. Validation of grounding line of the East Antarctic ice sheet derived by ERS-1/2 interferometric SAR data. Polar Geosci.
**2005**, 18, 1–14. [Google Scholar] - Gerrish, L.; Fretwell, P.; Cooper, P. Medium Resolution Vector Polylines of the Antarctic Coastline (7.5). UK Polar Data Cent. Nat. Environ. Res. Counc. UK Res. Innov.
**2022**. [Google Scholar] [CrossRef] - Murayama, H. General Characteristics of the Antarctic Lakes near Syowa Station. Antarct. Rec.
**1977**, 58, 43–62. [Google Scholar] [CrossRef] - Brenner, A.C.; Blndschadler, R.A.; Thomas, R.H.; Zwally, H.J. Slope-induced errors in radar altimetry over continental ice sheets. J. Geophys. Res.
**1983**, 88, 1617–1623. [Google Scholar] [CrossRef] - Bamber, J.L. Ice sheet altimeter processing scheme. Int. J. Remote Sens.
**1994**, 15, 925–938. [Google Scholar] [CrossRef] - Brenner, A.C.; DiMarzio, J.P.; Zwally, H.J. Precision and Accuracy of Satellite Radar and LaserAltimeter Data Over the Continental Ice Sheets. IEEE Trans. Geosci. Remote Sens.
**2007**, 45, 321–331. [Google Scholar] [CrossRef] - Raney, R.K. The delay/Doppler radar altimeter. IEEE Trans. Geosci. Remote Sens.
**1998**, 36, 1578–1588. [Google Scholar] [CrossRef] - Wingham, D.J.; Francis, C.R.; Baker, S.; Bouzinac, C.; Brockley, D.; Cullen, R.; de Chateau-Thierry, P.; Laxon, S.W.; Mallow, U.; Mavrocordatos, C.; et al. CryoSat: A mission to determine the fluctuations in Earth’s land and marine ice fields. Adv. Space Res.
**2006**, 37, 841–871. [Google Scholar] [CrossRef] - Slater, T.; Shepherd, A.; McMillan, M.; Muir, A.; Gilbert, L.; Hogg, A.E.; Konrad, H.; Parrinello, T. A new digital elevation model of Antarctica derived from CryoSat-2 altimetry. Cryosphere
**2018**, 12, 1551–1562. [Google Scholar] [CrossRef] [Green Version] - Wingham, D.J.; Ridout, A.J.; Scharroo, R.; Arthern, R.J.; Shum, C.K. Antarctic elevation change from 1992 to 1996. Science
**1998**, 282, 456–458. [Google Scholar] [CrossRef] - Ulaby, F.T.; Moore, R.K.; Fung, A.K. Microwave Remote Sensing; Artech House: Norwood, MA, USA, 1986; Volume III. [Google Scholar]
- Tadono, T.; Nagai, H.; Ishida, H.; Oda, F.; Naito, S.; Minakawa, K.; Iwamoto, H. Generation of the 30 m-mesh global digital surface model by ALOS PRISM. Intl. Arch. Photogram. Remote Sens. Spatial Inf. Sci.
**2016**, XLI-B4, 157–162. [Google Scholar] [CrossRef] - Ushio, S.; Wakabayashi, H.; Nishio, F. Sea ice variation in Lützow–Holmbukta, Antarctica, during the last fifty years. Seppyo
**2006**, 68, 299–305. [Google Scholar] - Nakamura, K.; Shigeru, A.; Tsutomu, Y.; Takeshi, T. Interactive movements of outlet glacier tongue and landfast sea ice in Lützow-Holm Bay, East Antarctica, detected by ALOS-2/PALSAR-2 imagery. Sci. Remote Sens.
**2022**, 6, 100064. [Google Scholar] [CrossRef] - Nakamura, K.; Yaginuma, S. Relationship between ice flow velocity of Shirase Glacier and its surrounding landfast ice derived from ALOS-2/PALSAR-2. In Proceedings of the the 73rd (Autumn 2022) Conference of the Remote Sensing Society of Japan, Isshindenkozubeta, Japan, 29–30 November 2022; pp. 269–270. [Google Scholar]
- Pavlis, N.K.; Holmes, S.A.; Kenyon, S.C.; Factor, J.K. The development and evaluation of the Earth Gravitational Model 2008 (EGM2008). J. Geophys. Res.
**2012**, 117, B04406. [Google Scholar] [CrossRef] [Green Version] - Watson, D.F.; Philip, G.M. A refinement of inverse distance weighted interpolation. Geo-Process.
**1985**, 2, 315–327. [Google Scholar]

**Figure 1.**(

**a**) Map of Lützow-Holm Bay, East Antarctica; the red line indicates the grounding line of the Shirase Glacier [21] and the green line indicates the grounding line of other glaciers and the coastline [22]. The blue rectangle defines the area of the Shirase Glacier analyzed in the present study. (

**b**) Locations of ponds in exposed rock area for the height validation in this study.

**Figure 2.**Schematic diagram of measurement performed using CryoSat-2/SIRAL over irregular terrain with slope.

**Figure 4.**Color-coded map of the estimated ice thickness distribution for the Shirase Glacier, as derived from (

**a**) the AW3D30 height and the CryoSat-2 height in (

**b**) 2011, (

**c**) 2012, (

**d**) 2013, (

**e**) 2014, (

**f**) 2015, (

**g**) 2016, (

**h**) 2017, (

**i**) 2018, (

**j**) 2019 and (

**k**) 2020. The red line indicates the grounding line of the Shirase Glacier [21] and the black line indicates the grounding line of other glaciers and the coastline [22].

**Figure 5.**Mean ice thickness profile from 2011 to 2020, extracted at 5 km intervals along the central streamline of the glacier. Ice thickness derived from (

**a**) the CryoSat-2 height and (

**b**) the AW3D30 height.

**Figure 6.**The relationship between ice thickness estimated on the basis of the AW3D30 height and that estimated on the basis of the CryoSat-2 height in the range of 10–40 km downstream from the grounding line.

**Figure 7.**The relationship between the ice thickness and the ice flow velocity assuming an incompressible fluid and the law of conservation of mass. The schematic diagram illustrates (

**a**) that there is no change in the ice thickness, while (

**b**) the ice thickness decrease $\Delta H$ is associated with the acceleration in flow velocity $\Delta v$.

**Figure 8.**The annual mean of ice thickness at 25 km and 30 km downstream from the grounding line of the Shirase Glacier.

Specification | Value |
---|---|

Agency | ESA |

Launch date | 8 April 2010 |

Satellite altitude | 717 km |

Repeat cycle (Sub-cycle) | 369 days (30 days) |

Sensor | SIRAL |

Frequency | 13.575 GHz (Ku band) |

Footprint (SIN mode) | 0.25 km (Along track) 1.60 km (Across track) |

**Table 2.**The amount of CryoSat-2/SIRAL data used in this study. Data for the Shirase Glacier are indicated without parentheses, and those used for validation are indicated with parentheses.

Year | Amt Data | Year | Amt Data | Year | Amt Data | Year | Amt Data | Year | Amt Data |
---|---|---|---|---|---|---|---|---|---|

2011 | 28 (5) | 2012 | 32 (5) | 2013 | 30 (4) | 2014 | 34 (5) | 2015 | 31 (9) |

2016 | 31 (7) | 2017 | 31 (5) | 2018 | 30 (4) | 2019 | 32 (7) | 2020 | 36 (8) |

Year | Measuring Points | Removed Ratio | Year | Measuring Points | Removed Ratio | ||
---|---|---|---|---|---|---|---|

Original | After QC | Original | After QC | ||||

2011 | 1032 | 262 | 74.6% | 2012 | 989 | 213 | 78.5% |

2013 | 869 | 160 | 81.6% | 2014 | 853 | 207 | 75.7% |

2015 | 927 | 175 | 81.1% | 2016 | 969 | 248 | 74.4% |

2017 | 841 | 157 | 81.3% | 2018 | 1008 | 272 | 73.0% |

2019 | 1018 | 252 | 75.2% | 2020 | 985 | 206 | 79.1% |

**Table 4.**The mean and standard deviation of the CryoSat-2 height and the AW3D30 height for each of the ponds in the exposed rock areas, as described in Section 2.1.

Pond Name | CryoSat-2 (m) | AW3D30 (m) |
---|---|---|

Maruwan O-ike | 6.33 ± 1.61 | 10.38 ± 0.52 |

Dairi Ike | 48.57 ± 0.71 | 50.97 ± 0.44 |

Skallen O-ike | 7.83 ± 1.26 | 12.87 ± 0.92 |

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## Share and Cite

**MDPI and ACS Style**

Satake, Y.; Nakamura, K.
Temporal Variations in Ice Thickness of the Shirase Glacier Derived from Cryosat-2/SIRAL Data. *Remote Sens.* **2023**, *15*, 1205.
https://doi.org/10.3390/rs15051205

**AMA Style**

Satake Y, Nakamura K.
Temporal Variations in Ice Thickness of the Shirase Glacier Derived from Cryosat-2/SIRAL Data. *Remote Sensing*. 2023; 15(5):1205.
https://doi.org/10.3390/rs15051205

**Chicago/Turabian Style**

Satake, Yurina, and Kazuki Nakamura.
2023. "Temporal Variations in Ice Thickness of the Shirase Glacier Derived from Cryosat-2/SIRAL Data" *Remote Sensing* 15, no. 5: 1205.
https://doi.org/10.3390/rs15051205