So starting late last week, we began to notice an anomaly with the flight patterns of Challenger. On down casts, we were seeing a number of heading errors, causing us to fly irregularly. This spurred a number of questioned followed by a brainstorming session to figure out what could have caused this. After all, before deployment, the compass had been calibrated and was working well. Ideas that we bounced around ranged from looking into a recent solar flare, positions of lows in ozone concentration, and high levels of ambient iron in the water; all of which could result in abnormalities in electronic compass readings. Finally, our team began looking into similar instances we have had where a gliders compass had acted in a similar manor. One of these instances that came to mind was a few years back when RU26 was flying in the Ross Sea off of Antarctica. After doing some research, it was discovered that both the region off of South Africa and the Ross Sea are both areas with abnormal lows in the horizontal intensity of the Earths Electromagnetic field.
Now, we think that the problem we are encountering is that this low in horizontal intensity combined with the angle we were diving at causes our compass to have errors in the eastern quadrants, impeding our ability to have complete control of our direction on dives.
Since we have hypothesized this as the reason for our abnormal flying, we have done a number of tests diving at different angles and have now chosen to fly at 20˚ on dives and 25˚ on climbs.
While we were running the tests, we lost a bit of position on the eddy we are flying through, so I have now plotted not only the currents, but the U and V components to find the best route North and West safely into international waters.
Based off of these maps, we have placed the waypoint up to the North West hoping to weave our way between the fluxes while avoiding crossing into Namibian waters. Other quick changes we made today were that low power mode has been turned back on at intervals of 30 seconds and current correction has been switched off so we can get a feel of how we can fly.
As for our boy Silbo to the north, he is still pushing along through the northern flux from a cold eddy to our south west.
Antonio has created another fascinating tool with the help of GeoEye and SeaStar showing correlations between the eddies and the depth of the thermocline.
From this map, we can see the presence of these eddies causes changes of up to 100m in the depth of the thermocline as we fly from warm eddy to cold eddy.
With the map above of sea surface height and currents with the overlay of the direction of the eddies, we can see that Silbo is continuing to fly due south between the influences of the large warm and cold eddies to the south east and south west respectfully.
Finally, Antonio left us a 3D map of salinity showing that starting from the Amazon and working out across the North Atlantic showing the range of 34 to 37: an incredible change for distance of 2000km
Force Wind Sea & Honor