Gulf Oil Spill – Radar Satellite Image May 8, 2010

Our friends at CSTARS just posted this stunning image. Taken by the Canadian-operated radar satellite, RADARSAT-2, it clearly shows oil slicks and sheen spread across a wide area (about 5,025 square miles, or 13,000 km2) in the Gulf of Mexico early this morning (May 8):

RADARSAT-2 image of the Gulf of Mexico, May, 8, 2010 – Source: CSTARS

We’ve added some analysis to help you armchair interpreters. Oil slicks look dark on radar images because the oil reduces the surface tension of the water, dampening (smoothing out) the small wavelets that normally roughen up the surface of the ocean. But any smooth water will look dark on radar, so not all dark patches are caused by oil:

RADARSAT-2 image with SkyTruth analysis, May 8, 2010.

 

UPDATE 5/8/10 7:00 pm – The first attempt to place a 70-ton containment box over the main leak failed today; the box has been moved aside and is being troubleshooted, and tar balls have begun to wash up in Alabama. The leak is continuing unabated, at a rate we calculate to be about 1.1 million gallons (26,500 barrels) per day – five times higher than the last official estimate (5,000 barrels per day) the Coast Guard made, before they quit making estimates a few days ago, admitting they had no accurate way to estimate the spill rate.

We estimate more than 18 million gallons of oil have spilled so far.

Now we can do a heads-up comparison of the RADARSAT-2 image with this MODIS/Terra image taken about four hours later. Still some clouds obscuring portions of the slick; observable slick and sheen spans about 4,100 square miles (10,624 km2). Fresh oil is apparent around the location of the leaking well; it seems to be carried to the southeast, then gets caught up in a counterclockwise gyre in the currents:

Gulf Oil Spill – May 7, 2010

Here’s a look at some of the limitations of the NASA / MODIS satellite imagery. Today’s Aqua image, like those of the past few days, has suffered from problems that make it impossible to map the full extent of the slick: clouds, haze, nearshore turbidity, and plumes of sediment issuing from the Mississippi River outlet channels (the Terra image today is even worse):

Only the thickest part of the slick is visible, as brown ropy-looking stringers in the vicinity of the leaking well. We think thinner slick and sheen could actually be spread across a much larger area. Compare with this map published by NOAA, showing oil slicks from May 2 to May 6 as mapped by aerial surveys, and May 7 (orange) as predicted by their oil spill trajectory model:

NOAA map showing oil slicks May 2 – May 7, 2010.

Gulf Oil Spill – More Imagery Coming

We’re getting requests from folks wanting to see the latest satellite images of the oil slick in the Gulf of Mexico. It’s been cloudy the last couple of days, so the NASA /MODIS imagery hasn’t been very good; the latest we posted was from the afternoon of May 2. But observers tell me it’s clear and sunny in the Gulf today, so we’re hoping the MODIS images this afternoon will give us a clear look at the entire slick. We’ll process and post those images as quickly as we can. Follow us on Twitter – we tweet as soon as we upload anything new – and keep checking here and in the SkyTruth image gallery.

There is a gallery of radar satellite images here – radar cuts through the clouds and haze to show the ocean surface, and the slicks are clearly visible on the May 3 image. The drawback – this image only covers part of the slick. We hope to see some better coverage in coming days.

We’d like to see a systematic, Gulf-wide monitoring program established, so that when emergencies like this happen the stream of images from multiple satellite systems is immediately available to all who want to see it – including folks like the Bay St. Louis-area local emergency response guy who just called SkyTruth for assistance.

MODIS satellite image from the afternoon of May 4, 2010.

UPDATE 5/4/10 6:30 pm – And here it is. Today’s MODIS / Aqua image features a break in the clouds (just barely) to reveal much of the oil slick. Fresh upwelling oil is apparent around the location of the leaking well. Long tendrils of slick and sheen stretch to the east and southwest; the total area of slicks and sheen, possibly including patches of open water, is 3,260 square miles. Nearshore, things get complicated: there are pale bands of turbidity, probably caused by the recent stretch of high wind and waves; and a few dark streaks and elongated patches trending northeast that we interpret as low-wind zones (wind shadow, the result of light winds from the northeast this afternoon). But there could be patches of oil slick obscured by these features. To the south, heavy cloud may also be hiding some of the slick from this ongoing spill.

Gulf Oil Spill – New Spill Calculation – Exxon Valdez Surpassed Today

Figure 1. US Coast Guard map showing size and appearance of oil slick on April 28, 2010.

Dr. Ian MacDonald at FSU just produced a new spill-size estimate based on the US Coast Guard aerial overflight map of the oil slick on April 28, 2010. This map shows the slick covering 1,786 square miles (4,627 square kilometers). The bottom line: on April 28 there was a total of 8.9 million gallons floating on the surface of the Gulf.

That suggests a minimum average flow rate of slightly more than 1.1 million gallons of oil (26,500 barrels) per day from the leaking well on the seafloor. Since we’re now in Day 11 of the spill, which began with a blowout and explosion on April 20, we estimate that by the end of the today 12.2 million gallons of oil, at a minimum, have been spilled into the Gulf of Mexico.

The oft-quoted official estimate for the Exxon Valdez spill is 11 million gallons, although some think that is the lower limit of the likely range. It appears that we’ve just set a very sad new record.

Here is Dr. MacDonald’s calculation:

Deepwater Horizon spill estimates derived from USCG fly-over data (28 April 2010)

These estimates of the total volume of oil released by the Deepwater Horizon spill were derived from the USCG fly-over map (Figure 1). The map was geo-referenced in Arc Map and the areas of each of the slick types (dull oil streamers, etc) were measured with a planimeter tool. Thickness estimates for each slick classification were taken from the BONN guidelines as published in the NOAA field manual (Figure 2). Conservative values were used for each slick types. Note that the predicted average layer thickness are still very small.

Figure 2. Chart of oil thickness and appearance.


A human hair is approximately 100 µm (microns). The main slick, which corresponds to
the cross-hatched area was assigned a low value of 0.5 µm. We calculate a total volume of oil for this slick as 8.94 million gallons (212,000 barrels) (Figure 3). Considering that the oil in the water on April 28 has been deposited since the blowout and explosion on April 20, the flow rate should be on the order of 26,500 barrels per day. Some fraction of the total oil released will have been evaporated or emulsified and sunk in the time since the spill began, or collected by the response crews, so this should be considered a minimum estimate.

 

Figure 3. Volume of oil based on Coast Guard map (Figure 1) and thickness (Figure 2).

UPDATE 5/1/10 5:15 pm – Lots of cloud and haze but this afternoon’s MODIS satellite image shows the main body of the oil slick around the leaking well location.


Gulf Oil Spill – 2 Million Gallons – Per Day?

The Mobile, Alabama Press-Register has published an article by Ben Raines with an alarming prediction. If the leaking well in the Gulf of Mexico shrugs off all control – the crippled blowout preventer, the wellhead, and any remaining control valves or baffles impeding the flow of oil and gas through the well – the rate of spillage could go to a whole other level: as much as 2 million gallons (150,000 barrels) per day.

Schematic diagram of the leaking well and the relief-well drilling plan. Courtesy Times/Picayune.

This worst-case scenario is based on the fact that there are individual wells in the Gulf of Mexico that produce 1.26 million gallons (30,000 barrels) of oil per day. That’s a controlled rate of flow. If all control were removed, the flow rate would be higher. How much higher?

“Typically, a very good well in the Gulf can produce 30,000 barrels a day, but that’s under control. I have no idea what an uncontrolled release could be,” said Stephen Sears, chairman of the petroleum engineering department at Louisiana State University.