Rain Rain Go Away

Below is a post provided by our Federal Partners at NOAA.  The NEFSC Behavioral Ecology Branch in Sandy Hook, NJ has been sampling the ocean off Northern New Jersey before and after Hurricane Irene.  The post below was submitted by Dr. John Manderson after an early morning sampling run.

Where on earth did the ocean go? Or what is the estuary doing in the ocean?

The upwelling area off Tuckerton is very well sampled by Rutgers Robot gliders. But the ocean off the mouth of Hudson Raritan Estuary is also interesting. This morning the NOAA ECOS program which operates out of Sandy Hook measured hydrography and took some samples for nutrients off the mouth of the Hudson River.

Our plan was to do 20 stations to the Hudson Shelf Valley which we mapped out early this morning on the Stevens NYHOPS.  We know NYHOPS is good but we thought “there is no way the salinities in the ocean are that low”.  Actually the salinities were lower.  We got to many of the stations and had some data collected August 17 on a similar transect with which we could compare.

As background, below are some of the meteorological data measured at the Ambrose buoy (NOAA buoy 44065) just off the mouth of the Hudson Raritan estuary. The red lines in the two panels show August 12, the last date ECOS sampled the New Jersey transect, and today, September 2. The dips in atmospheric pressure and seawater temperature, and increases in wave height and winds speed associated with the passage of IRENE are clearly visible in the plots.

Below are the locations of ECOS plankton sampling stations on Aug 17 superimposed on the MARACOOS NHOPs model output for Salinity.  We took water column profiles at these 5 and an additional 13 stations that day.

Here are the temperature and salinity combinations for today and for August 17.  The colors indicate chlorophyll values were as high as 20 mg liter today (This could be chlorophyll as well as other colored organic matter).  The symbols are sized by depth.  Salinity in the upper few meters of the water column was <21 PSU all the way out to the Hudson shelf valley.  NOAA is not sure their CTD probe which measures water column properties reached the bottom today because of extremely high bottom current velocities.

The mode of surface salinity today was ~21 PSU which is lower than we often measured relatively high up in the estuarine tributaries during the summer.

Finally here are the oxygen and chlorophyll values measured on Aug 17 and Sept 2 along the transect.  The chlorophyll values are pretty extreme today and minimum dissolved oxygen measurements are lower than in August but still above 3 mg per liters (dotted red line).

NOAA ECOS will continue sampling next week using acoustic instruments as well as CTD probes.  These instruments will allow us to monitor the effects of Irene and the summer bloom on the distribution of various sizes of organisms, as well as water column properties in the coastal ocean outside the mouth of the Hudson River.

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Rutgers robots, sensors probe effects of Irene

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Glider update for August 31

A quick update of the gliders.  As I type we believe that the floating glider RU23 has been recovered.  the glider recovery is being coordinated by Chip who has is receiving support from Jeff Yapalater who reached to his broader fishing community.  Once I have their specific details, then we will trumpet their fantastic help.  The path of ru23 is shown below.  The point of the leak is clearly visible as the subsequent inertial motions. The large loop seen below is the path during the passage of Irene.

The currents of RU16 are strong, but despite the strong currents RU16 is making good progress heading back to shore. The current plans from EPA, NJ DEP and Rutgers  calls for this glider to continue  a series of cross shore surveys.  The surveys will allow us to monitor the ongoing conditions offshore where the oxygen levels continue to remain low below the thermocline.  The nearshore waters we have just entered shows the stratification has eroded.  The nearshore waters are warm and fresher than the waters seen during the passage of Irene.  The %oxygen saturation show higher values nearshore.  It will be of great interest to monitor what is happening in the middle of the shelf especially as the summer phytoplankton remains present despite the large hurricane and the oxygen levels remain low in the mid-shelf bottom waters.

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After the Hurricane, what is the impact on subsurface signatures?

Irene has passed and clean-up begins.  The RU16 glider which was deployed by EPA, NJ DEP and Rutgers was directed offshore to survive the hurricane.  It rode out the storm in deeper waters and has now been directed to head back inshore to continue its monitoring of the dissolved oxygen status in the New Jersey coastal waters.  Below we show the track so far for RU16.  Initially upon be directed inshore, the glider headed north, this reflected the strong currents that the glider could not overcome.  This is view is supported by the CODAR data, which did a fantastic job surviving the entire hurricane. Below is the 25 hour average of the CODAR field on the 28th when the glider was redirected onshore.  The glider is now making progress to shallow water.

What did the hurricane do to the water column?  Below we show three plots of temperature, oxygen and %oxygen saturation.  The passage of Irene is clearly visible in all three plots.  As was noted in blogs from yesterday the surface ocean cooled dramatically. This cooling represents many processes which include, but is not limited to, mixing upper water with the colder bottom water, the transfer of heat from the ocean to the atmosphere which helps fuel the storm, and/or the advection of new water past the glider.  The satellite maps yesterday suggested the entire shelf cooled, so the advection hypothesis seems unlikely. See picture from below. There was definitely enhanced mixing, but there is still clear stratification on the water column.  So while the must be some entrainment of cooler bottom water the storm was not sufficient to overturn the ocean. The cooling was largely observed in the upper mixed layer depth from the surface to the thermocline (for the glider this was down to 30 meters).  The water cooled by several degrees consistent with the SST imagery before and after the storm.

The oxygen data also showed also showed changes in response to Irene. Oxygen concentrations in the bottom remained low however there were some indication that the bottom water oxygen was slightly elevated during Irene, whether this was the storm or it reflected the conditions in the offshore water remains an open question.  This impact was also seen in the % oxygen saturation which takes into account the temperature effects of gas solubility.  So the decrease in % oxygen saturation is clearly a storm impact.  This could reflect the entrainment of low % saturation oxygen waters from below, and if you look carefully at the boundary you see the impact.  Once the storm passes and the sun comes out you can see the oxygen start to increase again reflecting photosynthesis.  The % oxygen values also recover very quickly indicating alot of the summer phytoplankton bloom remains.  So the biological hypothesis of why the oxygen declined in the surface layers is that during the storm deep mixing and heavy cloud cover for a prolonged period of time resulted in extremely light limited phytoplankton.  Therefore respiration rates would be high through the storm leading to declines in the oxygen concentrations.  This would disproportionately impact the surface layers over the bottom waters; however the sudden coicident changes in the water temperatures during the oxygen declines also highlights storm induced mixing.  Clearly several processes are in play, and this is a unique and rich data set that will be studied for years.  Great work glider team!

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Hurricane Irene quick look figures

Here is a collection of some of what we saw yesterday and today with Hurricane Irene.

First the MARACOOS view from google earth that we have grown used to – the Mid-Atlantic HF Radar network is coming back in the southern side of the region. The operations team is heading out to the shore sites in some locations to the south.  In New Jersey, travel is still limited by closed roads and flooded rivers. Maybe we’ll make it to the beach tomorrow.

 

Now a collection of MODIS satellite color images from our scientist/artists.

Here Lisa took her MODIS image from yesterday and expanded to the full east coast for the SECOORA/MARACOOS/NERACOOS powerpoints.  You see the sediment on the continental shelf in the South Atlantic Bight, the clouds of Irene over the Gulf of Maine, and the Mid Atlantic split between the two regimes with the eye of Irene over New Jersey.

Now the zoom into the Mid Atlantic combined with the Gulf of Maine, both with Irene for the image of Large Marine Ecosystem #7, the Northeast U.S.

I also like Matt’s image of the Mid Atlantic that he sent around today, especially the sediment coming out of the rivers onto the shelf.

In the images above, you can see some of the sediment heading out to sea with the Gulf Stream off Cape Hatteras.  Lets look at the same satellite today:

Lots of sediment in the water around Cape Cod to the north, and the sediment on the shelf in the south by Cape Hatteras is really heading offshore.

There was also major discussion of the cooling of ocean temperatures today.  Here are two images I chose from the AVHRR sensors on the NOAA-19 satellite.

First, before the storm, on August 24, the early morning image while it is still dark so that the sun has not heated the skin layer.  Surface temperatures on the shelf are about 25-26 C.

Now, after the storm, we look at the same satellite, also in the morning before the sun comes up.

Sea surface temperatures are down to about the 18-20C range.

Thats the surface map, but what about the subsurface?  How deep does the cooling go?  Was there mixing too? For answers to these questions,  you’ll have to wait for Oscar’s plane to land so he can post the vertical data blog.

And for fans of the bloom, Matt just sent this along with the subject “The Bloom Remains”.  Its todays Chlorophyll image:

 

Check it out at

http://orb.ceoe.udel.edu/maps/MARCOOS_CHL/Mid-Atlantic_1_Day_Chlorophyll

 

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And on to Canada – 11 pm Final Advisory

Advisory number 35, the last advisory generated by the National Hurricane Center.

A last look at Irene from space as it heads towards Iceland:

And a last look at the Mid Atlantic CODAR network that performed so well during this event.

As communications come back to our shore sites, we’ll see that many still operated during the storm.  The medium range codars covering the approaches to New York Harbor for DHS and DoD are back transmitting the real-time data as soon as the communications were restored.

Thanks to the people of MARACOOS for their response to Hurricane Irene. It is the combined efforts of the full MARACOOS team that made this blog possible.

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On to Vermont – 8 pm advisory

Just closing out the record – waiting for the last advisory from the Hurricane Center.

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Irene is leaving Massachusetts for Vermont – 5 pm advisory

National Hurricane Center expects there to be only one more update after this one.  Irene is going through its extratropical transition, with the rain displaced well to the north of the center.  Note that the warning areas have all turned blue to tropical storm warnings. Here is the track:

Here are the clouds to show the spatial scale:

And then we get the rain to the north:

Zooming into the CODAR data, we see the wind driven flows from Irene on the western side decreasing near the New Jersey and Long Island coast, and remaining tidal up by Cape Cod.

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Irene from space – with the eye over New Jersey

Here’s today’s MODIS visible image of Irene, with the eye located over northern New Jersey.

 

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Landfall, Tropical Storm & Extratropical Transition – 11 am guidance

Irene is now centered west of Connecticut and has been downgraded to a Tropical Storm, with Extratropical Transition expected in the next 12 hours.

The weather is clearing over the southern side of the Mid Atlantic Bight.

Looking at the areas of rain from the weather radars, we see much of the rain is now in Massachusetts, New York and Pennsylvania.

Zooming into the CODAR fields over the northern half of the region, the currents look like the weather forecasts from the last post.  They are heading away from the New Jersey coast, and towards Long Island and into the entrance to Long Island Sound.  East of Block Island we see the tidally dominated flows that surround Cape Cod. Immediately south of Block Island is the complicated transition zone between the tidally dominated flows to the east the the tropical storm forced flows to the west.

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