Iceberg A23a
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We saw this anomaly in the wave map. For its size it can only be A23a Iceberg.
(Fig 1)
However the position of the Iceberg is much further north.
(Fig 2)
When I change the model from ECMWF to GFS, another anomaly appears - closer to the position A23a should be.
But there's still that anomaly on the same spot next to S Sandwich isl. (Fig 3)
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@idefix37 The anomaly on my first image is further south than the actual position of A23a, closer to South Sandwich Islands - NOT north of South Georgia.
Your image of the satellite layer show the current position of the iceberg - but the anomaly I marked on my first image (a large object creating a wave shadow) can only be A23a - but it shows significantly further South than the current position of the iceberg.
As far as I know, there is no significant iceberg North of South Georgia - nor in the position of the anomaly on my first image.
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@idefix37
It looks like you are mistaking South Orkney island with South Georgia.
A23a is between South Georgia and South Orkney, closer to South Georgia. The satellite layer you posted has its correct position.
But the disturbance seen by Albatros is much further south, East of South Orkney. I had noticed it myself.
If the position of such large object is showing on the weather map so far away from its actual position, can we trust the accuracy of the position where the storms are? -
@BrazilNuts said in Iceberg A23a:
can we trust the accuracy of the position where the storms are?
Yes we can trust the position of the storms.
Just compare the position of a storm shown by a forecast model with the actual position from satellite image. -
@BrazilNuts said in Iceberg A23a:
@idefix37
It looks like you are mistaking South Orkney island with South Georgia.
A23a is between South Georgia and South Orkney, closer to South Georgia. The satellite layer you posted has its correct position.I don’t mistake South Orkney island S60°46’ with South Georgia S54°11’ !
None of my previous screenshots is showing South Orkney island !
You misinterpreted my screenshots.Yes, A23a is between South Georgia and South Orkney island as shown in this screenshot.
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Iceberg is not colocated with wave minimum !
The same shows on meteoblue (sign. wave height)
Looks like the model computes the iceberg in wrong position (or not at all).
Seems that GFS takes into account the iceberg's impact in the waves!
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@Gkikas-LGPZ
The ECMWF model positions A23a further south than the 60th parallel while the satellite displays it at latitude 56°S.
But I don’t see the anomaly in Waves layer by ECMWF that you were showing in your first screenshot.
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@idefix37
According to U.S. National Ice Centerhttps://usicecenter.gov/Products/AntarcIcebergs
A23a coordinates
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@Gkikas-LGPZ
Strange that the small one in NNE of South Georgia is not listed, may be too small ?
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@idefix37
I just provided the first rows of the list.
Criteria....
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@Gkikas-LGPZ
Thanks, I don’t find it. -
Today, GFS wave model shows the impact of the A23a iceberg on waves (similar to an island).
ECMWF doesn't seem to integrate the iceberg in the wave model (although the iceberg's size is bigger than model's grid). -
@idefix37 said in Iceberg A23a:
ECMWF model positions A23a
ECMWF positions sea ice (not iceberg) in that location.
According to https://codes.ecmwf.int/grib/param-db/31
"Sea ice is frozen sea water which floats on the surface of the ocean. Sea ice does not include ice which forms on land such as glaciers, icebergs and ice-sheets". -
@Gkikas-LGPZ
OK, but what is shown in “Snow depth and sea ice” screenshot by the red arrow ?
Is it ice pack alone at sea or around a small island. I understand this type of map can show some uncertainty. -
@idefix37
Sea ice. Frozen salted (sea) water that floated there because of the extremely cold atmospheric conditions in the area. Sea ice is not thick like icebergs and melted.
As ECMWF describes .... "Sea ice is frozen sea water which floats on the surface of the ocean. Sea ice does not include ice which forms on land such as glaciers, icebergs and ice-sheets. It also excludes ice shelves which are anchored on land, but protrude out over the surface of the ocean. These phenomena are not modelled by the IFS -
@Gkikas-LGPZ
Thank you. -
... so, fig.1 (ecmwf) of @Albatros_Exp shows wave minimum because of sea ice at 60°S
and fig.3 (GFS) shows two wave minima, one because of sea ice and the other because of A23a.
This is my explanation. True or not ... I'm not 100% sure! -
@Gkikas-LGPZ
You are probably right ! So ECMWF ignores the icebergs in its wave model. -
@Albatros_Exp
I was wondering the same thing. That object blocking the waves East of the South Orkney Islands is very big, as as far as I can tell, there's nothing as big in that position.
A23a is between South Georgia and Elephant Island. Several cruise ships are stopping by to see it.
