Ocean model output in support of Denman Terrestrial Campaign

[mmr0]

What do we expect to see at our Shackleton sampling/mooring site?

Wish list for pre-departure

• South/North and East/West transects of T & S intersecting (66.2129° S, 98.8425° E), roughly 20km long to cover prospective hot water drill (HWD) sites
• TS plots from two boxes outside the cavity for January, colored by depth. For both MITgcm and ACCESS

Ideas for later

• An estimate of the Cavity residence time for Shackleton and/or Denman?
• Current speed at (-66.2078, 98.8669) and its variability including tides. Variation over depth also of interest.
• TS plots from inside the Denman & Shackleton cavities

When? Campaign is early Jan, so summer data is most relevant. Would be interested to see summer vs winter perhaps?

Brief summary of the Hot Water Drilling: One borehole through the Shackleton Ice Shelf, near the western flank of the Denman Ice Shelf. Ice approx 200m thick, water column total depth ~600m, TBC. Data sampling will include CTD profiling, water sample collection, video logging and sediment collection. Following profiling, we will deploy a mooring with 2 x CTD (one near ice-ocean interface and one near seafloor, sampling @ 10 minute intervals) and 1 x current meter (near ice-ocean interface, sampling @ 30 minute intervals), and a distributed temperature sensing (DTS) fibre optic cable which will give meter-resolution temperature through both the ice and water column. Expected endurance of the ocean instruments is ~ 3 years. DTS data will be 1 year. At the surface, an APRES will collect basal melt rate data.

What do we expect to see near Duanne's epishelf lake sites?

Wish list:

• Summertime T & S transect from (-66.0987, 99.1761) to (-65.4753, 102.1599)
• Summertime T & S transect from (-65.413, 99.5659) to (-66.387, 100.453)

Any help on any of these would be amazing!!

[mmr0]

Box 1 lats = array([-65.4987, -65.7091, -65.6935, -65.4519]) lons = array([97.8152, 97.8152, 98.2762, 98.2574])

Box 2 lats = array([-65.3273, -65.5688, -65.561 , -65.2961]) lons = array([98.5867, 98.6337, 99.1606, 99.123 ])

[claireyung]

Some ACCESS-OM2-01 IAF Cycle 4 T-S Diagrams

Map:

T-S over 2000-2018 (monthly data):

Only Januarys:

Looks like some CDW coming in in Box2 but not in Box1?

[yuhang559]

MITgcm, RYF (1990-91), BedMachine bathymetry Map: (be careful the depth is the ocean depth or the ocean thickness - there is an ice shelf on the top of the ocean layer in the ice shelf region.) TS diagrams: Looks water masses in MITgcm are much colder than ACCESS :)

[mmr0]

Yiew, thanks @claireyung @yuhang559, this is awesome! Yeah it looks like Boxes 1 and 2 are pretty similar except for Box 1 being much shallower and excluding CDW in ACCESS and mostly excluding it in MITgcm. We definitely didn't catch any ISW haha. How do I interpret all this near-freezing point fresher water in MITgcm e.g. in Box 2 in Jan? is this freshwater from melted sea ice?

[mmr0]

Some papers:

Ribiero et al 2023 - Change in watermass properties east of Shackleton from historical -> recent data https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2023JC019882

Van Wijk 2022 - CDW observed in trough in front of/adjacent to Denman Ice Tongue from profiling floats https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2022GL100460

[yuhang559]

Yiew, thanks @claireyung @yuhang559, this is awesome! Yeah it looks like Boxes 1 and 2 are pretty similar except for Box 1 being much shallower and excluding CDW in ACCESS and mostly excluding it in MITgcm. We definitely didn't catch any ISW haha. How do I interpret all this near-freezing point fresher water in MITgcm e.g. in Box 2 in Jan? is this freshwater from melted sea ice?

Yes, the freshwater in MITgcm is both from the sea ice and the melting of the ice shelf.

[yuhang559]

MITgcm(RYF, tides) Current speed and two summer sections

Velocity map:

Velocity-depth figure (white circle in velocity map): Our model includes the tides, but we only save the monthly mean data, so it probably can't capture the tide variability and the velocity-depth figure shows the velocity is highly sensitive to the position of the dots.

TS diagram sections: To plot it conveniently, I interpolated the matrix, so section 1 and section 2 look in different resolutions.

[mmr0]

Thanks so much Yuhang, this is super useful!

MITgcm(RYF, tides) Current speed and two summer sections

Velocity map:

Velocity-depth figure (white circle in velocity map): Our model includes the tides, but we only save the monthly mean data, so it probably can't capture the tide variability and the velocity-depth figure shows the velocity is highly sensitive to the position of the dots.

TS diagram sections: To plot it conveniently, I interpolated the matrix, so section 1 and section 2 look in different resolutions.