[ecco-support] Question about the inconsistency between ECCO Version 4 Release 1 and the latest Version 4 Release 3

[Fenty, Ian G (329C)]

Qi,

Thank you for your question.  I am fairly certain that there are no in situ ocean temperature measurements in front of Totten used to constrain any ECCO state estimate at this time.  The recent observations in front of Totten published in Rintoul et al., 2016 have not yet been incorporated.

Looking at the figure S5 it appears that all three products are actually quite different quantitatively (SOSE: temperature range from +1 to -1 over a few years, ECCOv4R1: +.6 to +.2 over 24 years, ECCO2: 0.6 to -1.5 over 24 years.)  The ECCOv4 solutions are almost certainly too coarse to adequately resolve circulation on the continental shelf in front of Totten.  The warming over the first few years of the ECCOv4R3 solution may be due to spin-up.  After 1998 the ECCOv4R3 solution does show a vaguely similar qualitative pattern of cooling, slight warming, then cooling again.    However, I’m afraid that without observations it is not really possible to determine which of these solutions is closest to reality or if the qualitative changes reported by Li are real.

In the meanwhile, please take a look at Khazendar et al., 2013 Observed thinning of Totten Glacier is linked to coastal polynya variability in Nature Communications for a discussion on how sea ice can affect ocean temperatures on the shelf in the region.

Ian


On 3/26/18, 11:37 PM, "ecco-support-bounces at mit.edu<mailto:ecco-support-bounces at mit.edu> on behalf of Adam Liang" <ecco-support-bounces at mit.edu<mailto:ecco-support-bounces at mit.edu> on behalf of qi.liang.whu at gmail.com<mailto:qi.liang.whu at gmail.com>> wrote:

Hello ECCO groups,

My name is Qi Liang, and I'm a graduate student at Chinese Antarctic Center of Surveying and Mapping, Wuhan University, China. Recently I was doing some research on Antarctic glacier and its relationship with ocean forcing. The ECCO ocean potential temperature products provided me great help.

The ECCO Version 4 represents the latest ocean state estimate of the ECCO. Furthermore, the newly released  Version 4 Release 3 extended the time period to the year 2015 and includes some additional improvements. But I find some big differences between Version 4 Release 1 and Version 4 Release 3, as well as the ECCO2.

In the work of Li et al., (2016), he plotted the potential ocean temperature in front of Totten Glacier with SOSE, ECCO_V4 and ECCO2 products, respectively. The potential temperature is averaged between 450 m and 600 m depth, over a spatial domain spanning 115 E to 118 E and 65.5 S and 67 S. The figure looks like this: (Figure S5 in his paper)

[cid:ii_jejeilmn0_16208dfde4cc9c67]
As you can see, although there are some differences between those three products, the similar temporal trend of temperatures is obvious. However, when I plotted the ECCO Version 4 Release 3 product with the same area and ocean depth, it demonstrated a total different temporal trend, looks like this:

[cid:ii_jejev43l2_16208e915472171c]

It confused me and I've no idea which product should I use for the data analysis. I was wondering if you guys could give some advice about that?

Thank you for reading my message. If you have any questions, don't hesitate to let me know.


Best regards
Qi


Reference:
Li, X., E. Rignot, J. Mouginot, and B. Scheuchl (2016), Ice flow dynamics and mass loss of Totten Glacier, East Antarctica, from 1989 to 2015, Geophys. Res. Lett., 43, 6366–6373, doi:10.1002/2016GL069173.

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