Friday, March 30, 2007

Crossing fronts

RU16 is now moving toward the offshore end of the Rutgers University Glider Endurance Line. The glider crossed a strong temperature front (also seen in the sea surface temperature image from two days ago, see post below) and is now in surface rich chlorophyll waters. Once RU16 reaches the offshore waypoint, it will head onshore along the endurance line. RU01, the other glider currently in the waters of NJ, is already moving onshore along that line. RU16 will trail RU01 by about 4 days.

Wednesday, March 28, 2007

The crossing under the shipping lanes continues

The glider makes good progress as it heads under the last major shipping lane today and tonight. Hopefully tomorrow it will be smooth sailing on the open waters of the MAB. Interesting frontal boundaries, and as has been the case the last few days, lots of plants in the surface waters and non plant particles dominating the deeper water optical signals.

Approaching waypoint

RU16 continues to make solid progress toward the next waypoint. It will be there at sometime tomorrow.
The glider is almost over crossing a band of warm waters near the Hudson River Canyon. The warm waters are restricted to a thin band near the surface, as revealed by the glider observations. The variation near-surface salinity is much weaker. The chlorophyll concentration is high in the upper water column

Monday, March 26, 2007

Glider update

RU16 has been going back and forth along Eric Powell's fisheries transect for the last 3 days (see map below). It collected a total of 4 transects, which will give us information about short time variability in the hydrographic fields in the area. As soon as it hits the waypoint, it will head to the southwest toward the southern flank of the Hudson Shelf Valley.

Thursday, March 22, 2007

the nepheloid layer is present!!

The glider heads into the major zone of shipping activity next. crunch time on the ocean turnpike. interesting observation today is the nepheloid layer in the warm bottom water. the backscatter says lots of paticles are prsent with very little chlorophyll present. That means either sediment or detritus which is often what dominates nepheloid layers. The nepheloid layers often seem to be dominated by detritus which is "fluffy" and easily maintained up in the water column.

Almost at waypoint

RU16 is almost at the next waypoint. The southeastward velocities over the shelf are helping the glider fly very fast (24 km in 18 hours).

After reaching the waypoint, the glider will follow the green line in the plot above, coordinating with Eric Powell's fisheries cruise. The salinity section below reveals lots of small scale structure over the shelf. The glider is now in waters nearly homogeneous, with gradients only in the near-bottom layer.

Long Island source of CDOM water?

Here we have mean surface current map from the last 4 days. Notice the northeast section of the map...we see surface advection from Long Island heading offshore towards the shelfbreak and it goes right through the area RU16 was flying! So could Long Island be the source of the high CDOM water that we saw in the glider section? Interesting...

Wednesday, March 21, 2007

COOL CDOM WATERS, where do they come from?

The glider continues to make nice progress. We will now prepare to turn into the Glider zone of death (check out the ship tracks). We should have an exciting couple of days! The salinity (and temperature) show a zone that is unique. In the unique water mass, the lower salinity water shows very low chlorophyll but very cooly shows higher Colored Dissolved Organic Matter (CDOM). Next steps is check out the CODAR currents!!

Tuesday, March 20, 2007

Glider update

RU16 is now 2/3 of the way to the next waypoint. It will be very soon in the area where the current CODAR coverage extends. It seems like the glider will be facing some weak, opposing currents.

solid progress towards waypoint 2

RU16 is making solid progress to waypoint 2, we expect arrival within the next two days.
The glider track shows that RU16 has been moving in a nearly along-shelf direction on the second leg so far. Both CTD and optical data has both shown plenty of structures. We can see in the temperature section that we have just moved through a region of very cold water (< 5.5 deg C).

Sunday, March 18, 2007

Turbid deep water -- figures

The following figures go along with Oscar's previous posting. Please read his post first.

high backscatter signal at depth:
low corresponding chlorophyll signal:

Turbid deep water

The optical backscatter data again provides an interesting picture that shows turbid subsurace water with low chlorophyll. The high turbidity is associated with the warm and saline deep waters. now as the storm passes lets see if the biological activity starts picking up in the surface waters. the blogger has been great, I will start publicizing more to outsiders in the coming week.

Great work, and a fun flight for 100th celebration flight! osc

Surface Current on the New Jersey shelf

Here we have the mean surface current integrated from the beginning of March to now (March 18). The mean current north of the Hudson Shelf Valley is very weak inside the 100 m isobath.
Mean surface current map for the past 4 days shows mainly downshelf flow to the southwest.
The winter storm has left the region after dumping a couple inches of icy snow. Louis will have more on the post-storm analysis.

RU16 entering New Jersey shelf

After crossing the shipping lanes by running 12 hour missions using the new flight profiles, the glider has resumed its normal flight behavior heading for the next waypoint on the NJ shelf near the 60 meter isobath north of the Hudson Shelf Valley.
Latest data suggests that the glider is starting to encountering warmer/saltier slope water at depth below the 70 m isobath. The cross-shelf salinity (temperature) section shows an interesting fresh-salty-fresh-salty (cold-warm-cold-warm) pattern.
This is very different than what RU01 currently sees on the Endurance line south of the Hudson Shelf Valley, where we have significant intrusion of the slope water onto the shelf throughout the entire water column:
Next we'll look at the surface current during the month of March on the New Jersey shelf.

Saturday, March 17, 2007

Shelf response to storm

The NOAA RUC analyses provided by Louis shows the strong winds that hit the MAB last night.

The response over the shelf to the storm was very strong, with currents over 50 cm/s extending for more than 500km. RU16 is a bit to the east of where the radar coverage ends. The glider is cycling the full water depth again, after the shipping lanes were left behind.

Made it Across!

Josh sent around the morning email. RU16 successfully surfaced on the southern side of the shipping lanes. A new trail blazed between Massachussets and the shelf break. Josh will keep RU16 on this southerly course for most of today, surfacing every 3 hours to download data. Once we cross over the 100 m isobath, taking us well south of the shipping lanes, RU16 is programmed to turn right and head due west towards Hudson Canyon. There it will link up with Eric Powell's vessel on a fish research cruize.

Half way across

Josh and John sent RU16 across the first lane into the seperation zone. Checking the AIS data, no ships were reporting in the area. Data was downloaded. Back on a mission across the next lane. We'll know more in the morning.
They were able to download datstarted RU16 just 1 km north of the shipping lanes earlier this afternoon, and sent i

Friday, March 16, 2007

Glider at the shipping lanes

After staying down for 12 hours, the glider emerged just north of the shipping lanes. The mission worked just fine. The glider moved forward while oscillating between the bottom and 20 meters below the surface. Although we missed information at the surface layer, there is still significant variability at depth. The glider is scheduled now to fly for another 6 hours. We hope this will get the glider right in the space between the inbound and outbound shipping lanes, where it can safely stay at the surface for a few minutes while sending us back the data it collected. We are almost half way through the most dangerous part of the trip.

Thursday, March 15, 2007

Approaching the Shipping Lanes

Josh Kohut just sent word over email that RU16 completed our first 12 hour underwater leg.
We routinely do 6 hours without communicating, but this was our first time we intentionally stayed down for 12 hours. We are testing Josh Graver's new mission to stay deep and fly a specific compass heading for a long time regardless of currents.

The mission worked perfectly. The plot above shows no data above 20 m depth at the end of the section, indicating we did indeed stay deep. That means we are ready to approach the second danger point on this trip from Massachusetts.

The first dange point was leaving Martha's Vineyard. We have had trouble there before, and knew there would be strong tides. That strategy was simple - fly away from the danger point as fast and directly as you can. No need to zig-zag around.

Now we are approaching the east-west shipping lane into NY Harbor. This will be the difficult one. The plan is to approach the northern side of the shipping lane, then from the northern side,
stay deep and jump to the seperation zone in the middle. Once there, we repeat the stay deep mission and jump to the southern side.

Next surfacing is at 11:30 am tomorrow, and we should be near the northern side of the shipping lanes by then. At that point we have about 1 minute to take manual control of RU16. If RU16 does not hear from us that it is safe to stay at the surface in that 1 minute interval, its just going to dive back down deep into safer waters, and keep heading south at 12 hour intervals until we tell it that its safe.

the test

There is a grand experiment being conducted, the first 12 hr glider mission is being conducted now. This is our test before we arrive at the busy shipping lanes. Hopefully tomorrow we will have a new chunk of beautiful data!

Wednesday, March 14, 2007

Great day in Massachusetts

The efforts of the team lead to a great day and best of all we could honor Doug Webb who attended the activities at SMAST.

Current Glider data shows we have gotten beyond the low chlorophyll low sailinty water. interesting the backscatter was not as low, which I think means there is alot of nonalgal particles. Because the backscatter is not much higher here, it might be consistent with organic detritus, but this needs to teased out.

Glider update

The glider continues to make steady progress in its track south, having flown over 20 km in the first day. The salinity is low close to the coast in the surface layer, but rapidly increases in the offshore direction. The low salinity waters are characterized by very low chlorophyll concentrations, but relatively high particle load.



Wind forcing climatology

The figure above shows a 5-year average of the wind forcing over the western North Atlantic (from the Climatology of Global Ocean Winds – COGOW, Prevailing winds in the Middle Atlantic Bight (area marked by the blue box) are from the northwest during March, which should help in the glider flight to New Jersey.

Tuesday, March 13, 2007

stratified water column!

It seems that the inner southern New England shelf has already become stratified, granted the stratification is weak. The latest glider temperature section below shows a distinct thermocline at 20 meters. It is amazing to see that the water column structure has completely changed within a distance of 10 km cross-shore.

Biological response on the shelf

We saw in the earlier posting of satellite chlorophyll climatology for March that Nantucket Shoals and George's Bank are regions of high productivity. The shallow bathymetry combined with wind forcing lead to enhanced mixing, bringing nutrient to the surface for primary producers to use.

The question is what is the biological response on the southern New England shelf right now? We have seen in past satellite images evidence of patches of high chlorophyll water being advected downshelf and away from the Nantucket Shoals. Does such a patch exist currently and is it within the glider's sampling region?

Figure below, generated by COOL lab graduate student Ramya Ramadurai, shows the latest chlorophyll ocean color image for March 11 from the MODIS Aqua satellite. We see patch of high chlorophyll water moving off the Nantucket Shoals downshelf towards the southwest.
We could retask the glider to go check out the high chlorophyll patch. We will need to take prevailing current and shipping lane traffic into consideration however. The decision is yet to be made.

First data from RU16

Glider RU16 was deployed this morning and we post here the first set of data coming back. Here is the deployment map with the first way point (bullseye):
Tempereature section:

Salinity section:

For up to the hour update on the progress of RU16, please visit: