Author: Scott

RU29 is back in international waters.  As we move south, the warm layer of surface water is getting warmer, and is a bit deeper than earlier in the mission.

But the real story is in the salinity.  The subsurface salinity peak.

Thinking we should find us a RAMA buoy as we approach the equator.

RU29 flew straight east over Friday and Saturday until it passed north of the seamount.  With the strong northward currents, much of RU29’s flight has been eastward so far. Early Sunday morning the waypoint was changed back to Southeast, based on the depth average currents plots from the U.S. and European models. We are currently heading in the direction shown by the orange line. And we again are in international waters.  The yellow lines mark the EEZ limit for Brazil.  Hopefully the next EEZ we enter is South Africa’s.

Zooming out to the long view, below is the South Atlantic Basin.  RU29’s trip around the basin is divided into 3 legs. Leg 1 (blue) was from Cape Town, South Africa to Ascension Island in 2013.  Leg 2 (green) was Ascension to Ubatuba, Brazil in 2014.  Leg 3 (red) is one potential flightpath back to Cape Town via Tristan da Cunha. We’ll keep this red line up as a reference.  We are currently flying along the orange line.  Total great circle  distance to Cape Town from the present location is 5,600 km.  Assuming a strong speed of 25 km/day, its about 7.5 months to cover this distance. Again assuming all goes well, that gets us to Cape Town about March 2016 at the earliest.  We are leaving tropical Brazil during the southern hemisphere winter.  As we fly southeast, we will transition into southern hemisphere summer, hopefully arriving Cape Town as their summer is ending.

Compare today’s currents (below) with those in yesterday’s blog entry.

Yesterday we had currents to the north for a few hundred kilometers, followed by a longer region of currents to the south.  Today we have the opposite.

We’ll need to look closer at our forecast tools.

RU29 has a cluster of seamounts due east of it.  Over the weekend we tried to pass to the south, but our trajectory says no.  Strong currents to the north prevented us from heading on a southeast track. We checked the current forecasts for an alternative plan.

Below is the RTOFS forecast for today.  Strong currents to the north for the next few hundred kilometers.  Followed by strong currents to the south.

We are planning to change the waypoint to due east.  Combined with the current to the north, the glider trajectory will be northeast, and we will pass north of the seamount cluster.  We’ll then continue into the southward flowing currents, and let the ocean take us back south.