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Arctic sea ice / Re: Arctic Ocean salinity, temperature and waves
« on: November 21, 2020, 02:51:42 AM »
Yermak plateau area. 36 hour loop
Band I4 inverted colors
Band I4 inverted colors
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Something is definitely going on hereSome of this is surface wetness from rain.
Know of anywhere this data is available? I've been looking, can't find it. I've sent a couple emails to the RAMMB folks inquiring about it, and asking if there was a way to add it to the slider. No response yet. Perhaps if others also ask, we could talk them into adding it.
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NOAA-20 formerly JPSS-1 has an improved microwave channel and a design life of 7 years it was launched November 2017 22 bands from 23 GHz to 183 GHz. Nadir resolution 15.8-74.8 km 32 kbps in addition to the Advanced Technology Microwave Sounder (ATMS)
6.925/7.3, 10.65, 18.7, 23.8, 36.5 and 89 Ghz resolution from 3 to 62km
Turbulent mixing near the Yermak Plateau during the Coordinated Eastern Arctic Experimenthttps://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/92JC01097
Abstract
Recent current measurements obtained from drifting platforms over the Yermak Plateau in the eastern Arctic Ocean confirm that the plateau is a region of greatly enhanced diurnal tidal currents. Modulation of the diurnal currents is clearly related to the plateau topography, as has been previously proposed. We show, however, that temporal variability due to spring‐neap modulation must also be considered in interpreting records from drifting platforms. We review simple models of tidal current amplification in this region and find that the previous assumption of near‐resonant, barotropic shelf waves propagating around the plateau's entire perimeter is inconsistent with the true topography. Instead, we propose that the diurnal variability is due to topographic shelf waves at the K 1 and O 1 tidal frequencies that are generated at points on the plateau's perimeter where the waves' group velocities are near zero. Observed cross‐slope variations in ellipticity, orientation, and magnitude of tidal oscillations are consistent with the presence of topographic waves generated in this manner. The topographic enhancement of the diurnal tide near the Yermak Plateau has important consequences for the sea ice cover, hydrography, and general circulation of this region. For example, the stress divergence applied by the tidal currents at the ice base greatly exceeds the typical divergence of the surface wind stress, and tides may therefore be important to local ice deformation. The strong cross‐slope tidal currents also appear to be responsible for the production of high‐frequency internal wave packets, which are associated with energetic diapycnal mixing in the pycnocline. We also consider the possibility that tidal rectification is responsible for a mean current transporting Atlantic Water clockwise around the plateau.
Effects of tides on the quasi-steady upwelling-downwelling regimes and water mass exchange between the Arctic and Atlantic Oceans.
Abstract
Astronomical tides are strong in the regions of the Arctic shelf and GIN Seas, with amplitudes reaching up to 4.4m in the Hudson Strait, 2-3m in the White Sea and greater than 1m in the Canadian Archipelago. If nonlinear friction is present, at the sea bed or within a stratification water column, periodical motions transfer energy to shear stresses with a substantial non-periodic component. Over bottom topography, anomalous bottom shear stress generates vorticity and vertical motions, resulting in either an ageostrophic circulation or geostrophic upwelling/downwelling of isopycnals. Using a pan-Arctic and a North Atlantic ocean-ice model, both of which explicitly resolve tides, we examine the effects of tides on the vertical motions generated by Ekman pumping near the sea bed and at the ice-ocean interface, and the stretching and tilting of vorticity. We found that tides significantly increase the intensity of vertical upwellings and downwelling regimes near the shelf break. We extend the semi-geostrophic two dimensional Eliassen -Sawyer equation and three-dimensional omega-equation to take into account the effects of tides. We also discuss the application of the equations for the analysis of watermass transformations and dense water overflow in the main gateways between the Atlantic and Arctic Oceans : Fram Strait, Yermak Plateau, Barents Sea shelf break, Denmark Strait and Faroe Channel.
Thanks JayW. Been wanting that for agesI agree, seems more expansive than what we saw last year. Wonder if it's due to ice thickness, perhaps due to the higher tide cycle, interesting for sure. I see it starting at roughly 7°E. I see a separate feature at 81.3°N at the ice edge that I don't see is directly related.
Even more active than I imagined. 280km from nearest land. I think that's 82.5N which puts the eddy near the white blob. https://col.st/5Us0O (available for a while)
It's nice to see several people are taking note of what's going above Greenland/the Lincoln Sea. This entire region just continues to surprise and I wish I understood more of the dynamics which facilitated such a vast separation plus an ever-widening crack.This is today. There is a lot going on. Interesting swirls in the open areas extending north from Greenland. Then there's the interesting feature in the lower right, and the subsequent waves propagating northward. After seeing this gif from blumenkraft.
As it appears (to my non-expert eyes) that clouds cause artifacts in the concentration products, the big question in my mind is whether they cause high-concentration streaks, or whether they cause low concentration streaks... Can some kind soul superimpose (and synchronize) the cyclone and the concentration images and prove it one way or the other?I'm not an expert, but I have seen enough artifacts caused by clouds and rain to agree, they do confuse the sensors. I'd also add that like worldview, these concentration/area products are stitching together multiple satellite passes over the course of 24 hours. When sea ice is moving around, I wonder how much this motion also plays into the final product. In my humble opinion, these figures should include error bounds to describe the inherent uncertainty in the data being displayed.
p.s. Of course it's also possible the storm causes actual concentration changes that appear to be in its shape. Would love an expert opinion.
Another view of that gap that has appeared near the pole.RAMMB contrast boosted.
Nice, though I'm not sure what band I4 is showing. Mercator temperature resolution is too low to show much change on the Ellesmere coast yet. Salinity is often a better indicator of up/downwelling. Here is the modelled 0m salinity jul1-24 and 0m temperature, jul18-24It's sensitive to temperatures. I was thinking insolation was playing a role as well. The eddies are interesting.
It could just be insolation, probably both.
A lot of MYI ice in the Beaufort that has not suffered big heat nor big storms. These things can quench the melting season if August weather come dull.They are currently breaking up under a weak cyclone. Same is happening near Banks island.
The comet was visible last night here in Calif. It was about halfway between the horizon and the Big Dipper at 9:45pm. Kinda fuzzy with the naked eye but nice using binoculars. You only see so many comets in one lifetime. I can remember where I watched four memorable ones.Quite visible in the Maine darkness. Snagged a few shots last night.
Spotted these cloud formations on Worldview today. First between Svalbard and Franz Josef Land, second between FJL and Novaya Zemlya. I was struck by their small scale "cyclonic" appearance, don't think I've noticed anything like them before. My first thought was thuderstorm, especially the first image. The central structure in each is about 15 - 25 miles across. Just wondering if I'm correct, I'd be grateful for any insight.These mesoscale lows adre actually pretty common, especially if you look at enough RAMMB imagery. Unfortunately, I don't think they are thunderstorms (not to say nT- storms can't happen in the artic), but isee them as nteresting circulations in the mid or lower atmosphere.
Jay, do you know, which band would be capable of showing the sediments?Geocolor would likely be best, but a far as individual bands, I've seen high resolution band I1 "red" pick it up (M5 "red" also), and band M4 "green". Sediment is normally brown, a color combination of red and green, so I'd use one of those. The green band could also pick up algae as well I'd think. When toggling though the bands, I'd say green does best.
So what are we actually seeing in these shots? The water temperature or sediments?It is shortwave IR, it's temperature, I've used it with GOES imagery as well.
Because if it's the sediments, we can assume river discharge.
JayW - great loop. If you watch the protruding arm it is really interesting to watch as the ice spreads and then contracts twice and is just starting a third expansion at the end of the loop - each time it contracts you can see it has also suffered significant melting. Not sure what is the cause - it is so regular it must be some tidal movement (or a pulsing upwelling?)Not every orbital swath can capture the area, so there's a roughly 12 hour gap between days that the JPSS satellites can't see, that's the "surge" you see. Otherwise, it's about 50 minutes between frames, sometimes 100 depending on image availability.
The face of the rest of the ice does not seem to be affected by whatever is cause that arm to 'pulse'.