TEN DOLPHINS STRAND ON CAPE COD DURING THE CHRISTMAS HOLIDAYS
by Captain David Williams
Deafwhale Society, Inc.
On 27 December 2008, Doug Fraser with the Cape Cod Times (link) reported that ten dolphins came ashore on Wellfleet and Brewster beaches. Of the five common dolphins washed up on the Brewster, two were successfully returned to the sea. Two were dead and one was euthanized by members of the Cape Cod Stranding Network. However, the rescuers were able to take three Risso's dolphins that came ashore in Wellfleet to Provincetown and release them.
The Deafwhale Society has been trying to predict when dolphins will strand on Cape Cod a month before the animals reach the beach. We content that pods of dolphins are injured (barotrauma) by pressure waves generated when the seafloor bounces up and down during an undersea earthquake. The injury causes damage to the pterygoid sinuses which aids the function of biosonar and diving; a dolphin with earthquake-induced barotrauma can neither dive and feed itself nor can it echonavigate.
Our research over 30 years has taught us that the most likely earthquakes to result in Cape Cod strandings are magnitude >5 events that occur between 53N and 63N southwest of Iceland along the Reykjanes Ridge and south-southeast of the southern tip of Greenland. This area is located on the northern edge of the warm waters of the Gulf Stream. On rare occasion we find suspicious events between 4.5 and 5 magnitude. These quakes usually occur at night in areas when the water is about 1,000 meters deep over the tops of the volcanic mountains along the mid ocean ridge. This is a prime squid breeding and egg laying area and the dolphins are here feeding on the squid.
We find that it usually takes anywhere from 22 to 50 days for the injured pod to swim from the epicenter to the Cape Cod area. It all depends on the speed and flow of the surface currents. It appears that the pods that take the longest time to get to Cape Cod are those that were caught up inside a circular current (eddy current). Those that arrive in 25 days or so are the ones who travel a straight path from the injury site to Cape Cod.
We also find that the pods stranding within ~25 to ~30 days of the injury are far more likely to survive than those that hit the beach 40 to 50 days after injury.
We had been monitoring seismic activity just in case an earthquake occurred that might cause a stranding. We planed to issue a prediction if a suspicious earthquake occurred.
On 17 December 2008 we searched the US Geological Service's data bank and got the following results:
FILE CREATED: Wed Dec 17 02:43:45 2008
Circle Search Earthquakes= 3
Circle Center Point Latitude: 65.000N Longitude: 25.000W
Radius: 1500.000 km
Catalog Used: PDE
Date Range: 2008/11/01 to 2008/12/17
Magnitude Range: 1.0 - 9.0
Depth Range: 1 - 600
Data Selection: Historical & Preliminary Data
CAT YEAR MO DA ORIG TIME LAT LONG DEP MAGNITUDE
PDE-Q 2008 11 04 060538.13 53.22 -35.24 10 4.4 mbGS
PDE-Q 2008 11 07 201740.70 71.68 -11.59 10 4.1 mbGS
PDE-Q 2008 11 07 214057.05 71.69 -11.82 10 4.7 mbGS
The three earthquakes were rather small and had occurred 40 days prior to 17 December. The events on the 7th were 1,000 miles north of Iceland near the Greenland coast and not considered as likely to produce a stranding than events southeast of Iceland. Still, there was a slight chance that a pod injured on 7 November might show up on Cape Cod by Christmas day since the 50-day travel period did not expire until 27th of December. But other than the November 7th event, there were no earthquakes to worry about from the 7th of November until the 17th of December. This prompted us to issue a prediction calling for no strandings until at least the 15th of January (link). As you can read, we did qualify this call be saying there was a 1% chance of a stranding on Christmas day.
It now looks like our 1% chance stranding came true. But there is one big problem. Risso's dolphins are not likely to be found midway up the east coast of Greenland, especially in November. The water is just too cold for Risso's. This species prefers warmer water and would be hanging around south of Iceland close to the warm waters of the Gulf Stream. This leaves us with the 4.4 magnitude event on 4 November, 51 days prior to the strandings. This event is also further south at 53.22N and right along the edge of the Gulf Stream. The odds are that an injured pod would travel east toward the UK, not back west. Besides, 4.4 magnitude is a bit low. each time you move up the magnitude scale by 0.3, the energy doubles. A magnitude 4.7 is twice as potent as a 4.4 so you can see why we honed in on the 7 November event.
Had a man-made explosion occurred? We have never witness in the last 30 years a mass beaching in which there were no earthquakes at sea that might explain it. In every mass stranding we have traced (over a thousand so far) there is always an earthquake or two to select, often there is 10 or more earthquakes. Still, we get a mass stranding after we predicted none would occur until at least after 15 January. How embarrassing for our theory and for 30 years of hard work.
We went back and double-checked the data (link) and discovered that an earthquake of 4.9 magnitude had indeed occurred southeast of Iceland dead center in the middle of the area where we had pinpointed scores of suspicious earthquakes over the past decades. This area is a known dolphin feeding ground where explosive volcanic-tectonic earthquakes are common.
We also discovered and event on 24 November a few hundred miles to the south. How and why the two events (in red) were not in the data bank is a mystery. Why the event on 11-24 does not include a magnitude number is also a mystery.
FILE CREATED: Sun Dec 28 22:47:51 2008
Circle Search Earthquakes=
5
Circle Center Point Latitude: 65.000N Longitude:
25.000W
Radius: 1500.000 km
Catalog Used: PDE
Date Range: 2008/11/01 to
2008/12/17
Depth Range: 1 - 600
Data Selection: Historical & Preliminary Data
CAT YEAR MO DA ORIG TIME LAT
LONG DEP MAGNITUDE
PDE-W 2008 11 04 060538.13 53.22 -35.24
10 4.4 mbGS
PDE-W 2008 11 06 102422.60
56.81 -34.14 10 4.9 mbGS
PDE-W 2008 11 07 201740.70 71.68 -11.59 10
4.1 mbGS
PDE-W 2008 11 07 214057.05 71.69 -11.82 10
4.7 mbGS
PDE-Q 2008 11 24 103221.25
53.16 -35.38 10
Now we can't be sure if the 6 November quake caused the stranding are not. Nor can we be sure that another group is not on the way to Cape Cod. We do think the 11-24 event is a bit too far south to get caught in the eastward flow of the current. Only time will tell.
Misty Niemeyer of the Cape Cod Stranding Network watches over one of two Risso’s dolphins that stranded in the marsh off Lt. Island Road yesterday. A total of 10 dolphins came ashore over the past two days. Picture by Doug Fraser/Cape Cod Times
Read the entire SEAQUAKE SOLUTION starting at: http://www.deafwhale.com