BP / Gulf Oil Spill – MODIS Satellite Image – May 9, 2010

MODIS / Aqua satellite image, May 9, 2010.

Today’s MODIS satellite image from NASA shows plenty of oil slick in the Gulf of Mexico from the ongoing BP / Deepwater Horizon spill – slicks and sheen cover about 4,384 square miles (11,355 km 2) although clouds, haze and turbidity (again…) are possibly obscuring portions of the slick. Fresh-looking oil is still moving southeast away from the site of the leaking well, and appears to be caught in a counterclockwise gyre (a circular current at the ocean’s surface – not uncommon in the northern Gulf). This may be helping to keep most of the oil trapped close the the leaking well, although the slick also extends northwest to the fringes of the Mississippi Delta, and large patch of slicks is visible far to the west, in the vicinity of Port Fourchon.

We estimate this well is leaking at a rate of 1.1 million gallons (26,500 barrels) per day. At this rate, the spill has now exceeded 21 million gallons. Most news accounts of this spill are repeating a much lower estimate of 210,000 gallons (5,000 barrels) per day, an unexplained number that NOAA and the Coast Guard were using for a few days until they admitted a week ago that they couldn’t accurately estimate the flow rate. We think it’s better not to use any number at all than to lock in on an unrealistically low estimate that nobody currently supports. Read why we think that here.

BP / Gulf Oil Spill – How Big Is It?

Quite a lot bigger than the estimate being uncritically quoted throughout the media of 210,000 gallons (5,000 barrels) per day. That was the last “official” estimate made by NOAA and accepted by the Coast Guard back on April 29 (see timeline below). Before that, the Coast Guard estimates ranged from 336,000 gallons (8,000 barrels) per day, to zero, to 42,000 gallons (1,000 barrels) per day. None of these estimates has been publicly explained or substantiated. And on May 1, the Coast Guard and NOAA stopped trying to estimate the spill rate, with Admiral Thad Allen saying, “Any exact estimate is probably impossible at this time.”

But the media continues to report that oil is leaking into the Gulf at 5,000 barrels per day. At SkyTruth we estimate the spill rate is closer to 1.1 million gallons (26,500 barrels) per day, based on the size of the slick on satellite images and Coast Guard maps, and thickness estimates derived from visual descriptions of the slick. That puts us at a total spill of 21 million gallons so far.

Considering that there are deepwater oil wells in the Gulf of Mexico capable of producing >1.26 million gallons (30,000 barrels) of oil per day under controlled flow rates; and that the oil slick continues to grow in size even though it’s been under attack 24/7 by skimmer vessels, burning, chemical dispersants, and natural processes; our estimate seems quite conservative.

Why is it important to get this number right? This is about more than just liability, or PR. You can bet that our future response capacity is going to be overhauled and retooled based on this spill. If we low-ball the spill amount and rate, we run the risk of designing an inadequate new spill-response system that is doomed to fail the next time something this big occurs.

Here’s the timeline of spill estimates:

  • 4/22 – Deepwater Horizon rig sinks; Coast Guard estimates “up to” 8,000 barrels per day (bpd) is leaking – source
  • 4/23 – Coast Guard reports no leaking at all from the damaged well – source
  • 4/24 – Coast Guard reports well is leaking, estimates 1,000 bpd – source
  • 4/25 – BP repeats 1,000 bpd estimate – source
  • 4/27 – 1,000 bpd still the official Coast Guard and BP estimate – source
  • 4/27 – SkyTruth and Dr. Ian MacDonald publish first estimate that spill rate is 20,000 bpd – source
  • 4/28 – NOAA weighs in and raises the official estimate to 5,000 bpd based on aerial surveys “and other factors”; BP disputes this higher estimate – source
  • 4/29 – Coast Guard and NOAA repeat their estimate of 5,000 bpd – source
  • 4/29 – BP’s Chief Operating Officer admits new estimate of 5,000 bpd may be correct; “He said there was no way to measure the flow at the seabed and estimates have to come from how much oil makes it to the surface” – source
  • 5/1 – SkyTruth and Dr. Ian MacDonald publish revised estimate of at least 26,500 bpd – source
  • 5/1 – Coast Guard Admiral Thad Allen “acknowledged there was no way really to know the extent of the leak” – source – and stated that “Any exact estimate is probably impossible at this time” – source
  • 5/1 – Coast Guard and NOAA cease estimating the rate of the spill. BP continues to use 5,000 barrels per day as their estimate of the spill rate.

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.