Sea surface height anomaly and geostrophic velocity from altimetry measurements over the Arctic Ocean (2011–2018)
Abstract. In recent decades the decline of the Arctic sea ice has modified vertical momentum fluxes from the atmosphere to the ice and the ocean, thereby affecting the surface circulation. In the past ten years satellite altimetry has contributed to understand these changes. However, data from ice-covered regions require dedicated processing, originating inconsistency between ice-covered and open ocean regions in terms of biases, corrections and data coverage. Thus, efforts to generate consistent Arctic-wide datasets are still required to enable the study of the Arctic Ocean surface circulation at basin-wide scales. Here we provide and assess a monthly gridded dataset of sea surface height anomaly and geostrophic velocity. This dataset is based on Cryosat-2 observations over ice-covered and open ocean areas of the Arctic up to 88° N for the period 2011 to 2018, interpolated using the Data-Interpolating Variational Analysis (DIVA) method. Geostrophic velocity was not available north of 82° N before this study. To examine the robustness of our results, we compare the generated fields to one independent altimetry dataset and independent data of ocean bottom pressure, steric height and near-surface ocean velocity from moorings. Results from the comparison to near-surface ocean velocity show that our geostrophic velocity fields can resolve seasonal to interannual variability of boundary currents wider than about 50 km. We further discuss the seasonal cycle of sea surface height and geostrophic velocity in the context of previous literature. Large scale features emerge, i.e. Arctic-wide maximum sea surface height between October and January, with the highest amplitude over the shelves, and basin wide seasonal acceleration of Arctic slope currents in winter. We suggest that this dataset can be used to study not only the large scale sea surface height and circulation but also the regionally confined boundary currents. The dataset is available in netCDF format from PANGAEA at [data currently under review].
Francesca Doglioni et al.
Francesca Doglioni et al.
Acoustic Dopper Current Profiler (ADCP) from moorings taken in the Eurasian and Makarov basins, Arctic Ocean, 2015–2018. Arctic Data Center https://doi.org/10.18739/A2HT2GB80
Physical oceanography and current meter data (including raw data) from FRAM moorings in the Fram Strait, 2016–2018 https://doi.org/10.1594/PANGAEA.904565
NABOS II – ADCP Water Current Data 2013–2015. urn:node:ARCTIC https://doi.org/10.18739/A28G8FJ3H
Physical oceanography and current meter data from moorings F1-F14 and F15/F16 in the Fram Strait, 1997–2016 https://doi.org/10.1594/PANGAEA.900883
Francesca Doglioni et al.
Viewed (geographical distribution)
The manuscript describes a new Arctic-wide sea surface height and geostrophic current velocity data set with a monthly resolution from 2011 to 2018 using CryoSat-2 data. They aim at documenting their product, describe the methodological steps, and final make a comparison to other products in various ways. This has been done!
The manuscript is well written, and structured in a fine manner. Though, it is a problem that the authors compare their dynamic ocean topography with a product with a different geoid and not even mention it.
The languish is fine. There are some grammatical errors and funny formulations, but all in all a nice written manuscript.
The authors need to fix the plotting issue around -180/180 longitude, and I am missing a location map of the moorings.
L74-75: I am a little puzzled about these sentences. Changes in steric and mass are normally referred to changes in absolute sea level which could be dynamic ocean topography or sea level anomaly!?
L90-94: In Armitage et. al. 20220, Nature, they include density. Why are you not including this? When are the balance valid?
L102: Which retracker is used?
L183: Which tide model is this? Is it the same as the altimetry?
L195: How are leads detected?
L245: I do not understand the sentence, please reformulate.
L258: What are causing the striping effect? Have you studied the effect of the chosen geophysical corrections? Could it be due to the rather old tide model you have used?
Fig 5: Caption (c). You should add that it is an interpolation error.
L297: What is a good score, as small as possible, can you be more precise?
L318: You should mention, that the 4.2 cm comes from the cross-over error
L323: Have have you derived the 3.5 cm? Are you assuming that the standard deviations are independent?
L373: “can be appreciated” how and why?
L379-380: How are you getting the average, are the numbers in cm?
Fig 6b: What are causing the bands in the plot?
L397: Your are comparing two data sets with different geoid? Then you will see the geoid difference as well!
L405: What is η’i?
Fig. 7 + text: Why are the errors following the bathymetry? Could this be differences in the geoid?
Table 5: assume it is for the total comparison. How have you calculated the total values?
L419: I may have missed it, but are you not comparing your data to all the moorings in table 1 and 2? If not please, delete or mark them in the table as not used.
Table7, L432-440: You should rewrite this section. I do not completely follow what you have done. What is distance covered in table caption? Distance between the moorings? Are the altimetry data averaged in the same distance? Also make a reference to section 4.5, were you describe the tests.
L441-442: Please, rephrase the sentence.
Fig. 9: Very nice figure, but what is panel (c). Are you missing something?
L495: How are these surface classifications different?
L571: Explain the deviations from the harmonic fit fig. 11c
L609-610: Do not follow the last sentence
Title: I suggest to change geostrophic velocity => geostrophic current velocity (for clarification)
L6: comma: Here,
L:39-40: It would be appropriate to mention ICESat-2. ICESat-1’s coverage is 86 lat, so almost the same as CryoSat.
L:59: Do you mean indicate? Could you be more specific?
L117: The figure should already be introduced in the introduction
L132: Move sentence Data are available... to the top of the paragraph.
L509: we took two steps => performed/prepared to analyzes??