Where Did the Gulf Stream Go?

 

At local apparent noon (LAN) for 14 April 1912, Titanic was approximately at 43 02'N, 44 31'W at 14:58 GMT, or about 126 nautical miles from the Corner point at 42N, 47W.  Her course to the Corner would be about 241 true. Over the previous 24 hours and 45 minutes, from LAN 13 April to LAN 14 April, Titanic ran a distance of 546 nautical miles averaging 22.06 knots.  However, we are told that Capt. Smith set the time to alter Titanic's course upon reaching the Corner at 5:50pm Apparent Time Ship (ATS), or 5 hours 50 minutes past LAN. If we divide the distance to the Corner by that time interval we get a speed of 21.6 knots, or knot less than the speed-made-good the day before despite carrying the same number of revolutions per minute on her engines.  It is possible that Capt. Smith may have anticipated an additional knot extra head current in setting the time to alter the ship's course at the Corner, or did he simply decided to take his ship a little beyond the Corner as surmised by 4th officer Joseph Boxhall?

 

But the real question is this. Did Titanic actually encounter an extra knot head current in her run from LAN to the Corner that Sunday?   If we add the distance from LAN to the Corner to the distance from the Corner to a collision point taken just north of the wreck site at 41 46' N, 49 56' W [see Collision Point], we find a total distance made good of about 258 nautical miles, a distance consistent with a taffrail log reading that showed that the ship traveled 260 miles through the water from noon to the time of collision. To cover 258 miles in 11 hours 40 minutes from LAN to the time of collision, the ship would have averaged 22.11 knots, about the same average speed as she was doing from noon Saturday, 13 April, to noon Sunday, 14 April, when she averaged 22.06 knots. So it seems that Titanic had not slowed down by an extra knot in that area after all. But if not, why not?

 

The answer lies in the fact that the Gulf Stream is far from being a stationary current. Looking at satellite radar imaging taken over a ten-year period for the 14th of April, from 2003 through 2012, we see a great deal of variability in the Gulf Stream and other currents in the area where Titanic foundered. Superimposed on these radar images that are shown in the sequence below is the route that Titanic was following on 14 April 1912, including her LAN position for 14 Apr 1912, the alter course point at the Corner (42N, 47W), the location of the wreck site, and the intended arrival points at the Nantucket Shoals and Ambrose Channel light vessels near the North American coast. (The date of each frame is shown in the upper left side in the format YYMMDD; thus, 030414 = 14 April 2003.)

 

 

Of particular interest, notice the area of the Corner point that is expanded in the following image for 14 April 2005.  Notice that from the location of Titanic's 1912 noontime position to the Corner, the track would pass through an area where the current was running north-northwest, part of a clockwise eddy flow that formed in that particular region. This component, running perpendicular to the track line, would not have slowed a ship's forward progress toward the Corner. It would, however, set a vessel traveling at 22 knots perhaps a mile or two to the north-northwest of the track line based on the strength of the current shown and the width of the area that a ship on that course line would be passing through. Beyond the Corner point to the wreck site location, a measurable current on 14 April 2005 was almost non-existent.

 

 

The main component of the Gulf Stream in April 2005 can be seen well to the south of the line from the Corner to Nantucket. We know that Carpathia, which was heading eastward down around 41 10N latitude, was being carried along by the Gulf Stream in the late afternoon and evening of 14 April 1912 based on passenger reports (e.g., Howard Chapin) of relatively high temperatures that forced them to lay aside their steamer rugs and coats and towards evening and seek shadier parts of the deck in order to be comfortable.

 

The Gulf Stream Current is a warm-water current that follows the eastern coastline of the United States and Newfoundland before crossing the Atlantic Ocean toward Europe. Its northern extension towards Europe is called the North Atlantic Drift. At about 40N, 30W, it splits in two, with the northern stream crossing to northern Europe and the southern stream re-circulating off the west coast of Africa. The Labrador Current is a cold-water current that flows from the Arctic Ocean south along the coast of Labrador and passes around Newfoundland and continues south along the east coast of Nova Scotia. It meets the warm Gulf Stream at the Grand Banks southeast of Newfoundland. The Labrador Current, which brings both icebergs and field ice down past Newfoundland, sweeps across the banks in a generally south to southwest direction, flowing more westerly on its surface as it approaches the warm Gulf Stream waters where it tends to under-run the warmer surface water where the two currents converge.

 

The following image shows water temperatures of the North Atlantic on 12 April 2003. The temperature scale is in degrees Celsius. The conversion from degrees Celsius (C) to degrees Fahrenheit (F) is: F = C 9/5 + 32. Also shown on this chart is the route taken across the Atlantic by Titanic in 1912 and her noontime positions for April 12, 13 and 14. Notice that the route between 40W to 47W longitude would have taken the vessel in waters of about 15C (about 59F) on that date.

 

 

The image below shows the velocities of the currents in the North Atlantic on that exact same date, 12 April 2003, taken from satellite radar imaging data. (Note, the colors in this radar image show the speed of the current, not the water temperature, at any given point, while the little arrow vectors show the direction of the current at that point.) The speed scale is in meters per second (m/s), and the conversion to knots is 1.94 knots per m/s. Also marked on this chart is Titanics route across the Atlantic, her noontime location for 14 April 1912, the Corner turning point, the location of the wreck site, and the course from the Corner to the Nantucket Shoals lightship and then on to the Ambrose Channel lightship.

 

 

Pilot Charts give long term averages of wind and current in an ocean area for a given month.  They can be used to show what might be expected along a certain route of travel. The green arrows on the chart indicate the prevailing direction of the ocean current, and the numerals next to them show the mean current strength in knots. The image below is from a Pilot Chart of the North Atlantic for the month of April.  Added to this is the route taken by Titanic (shown in red) in 1912.  [Also added are Titanics 1912 noontime positions for April 12, 13 and 14, and the location of the westbound Corner point (42N, 47W) in April 1912.]  

 

 

Notice that the Pilot Chart indicates an expected head current of about 0.5 knot on Titanic's route of travel for that portion of her route from noontime Saturday, 13 April, down to the Corner point. This of course would also have affected her run from noontime Saturday to noontime Sunday when she averaged a speed-made-good of 22.06 knots against this typical easterly flow of the North Atlantic. (We can also see this in a number of images in the 10-year sequence shown previously for the part of the track from 40W to Titanic's April 14th LAN position in longitude 44 31'W.)

 

Both the thermal and velocities imaging charts above show that the northeastern extension of the Gulf Stream on 12 April 2003 would have affected the Titanic, or any other vessel on that route, from about longitude 40W down to the Corner point at longitude 47W, and to a lesser extent from the Corner to the wreck site location. The velocities image shows current speeds from 0.3-0.6 m/s encountered from 40W down to the Corner with directions that would produce a head current to a current off the port beam for a ship heading down to the Corner point on that route. After the turn at the Corner, the ship would face a head current of about 0.1-0.2 knots to the wreck site location.

The same ocean currents existed in 1912 as they do today. But ocean currents are not stationary. They shift over time, usually taking several days to make small enough changes to be noticeable. Thanks to modern day satellite radar imaging, these shifts can be seen and tracked over time. For example, the sequence below shows how the velocities of the Gulf Stream changed in 7-day increments over a period of just 26 weeks from 29 December 2011 to 21 June 2012. (The date of each frame is shown in the upper left side in the format YYMMDD; thus, 110429 = 29 December 2011, and 120419 = 19 April 2012.)

 

 

We of course cannot say for certain what the exact situation was on 14 April 1912.  But what we can see from these modern day satellite radar images is that the currents in this part of the Atlantic are anything but predictable. Even less predictable is when you find two strong currents converging like that shown in the expanded image below where we see a relatively strong Labrador current converging with a strong Gulf Stream flow in the vicinity of the Titanic wreck site. Given the measured southerly drift of wreckage seen on the morning of 15 April 1912, as well as the temperature data taken by the SS Californian showing a sudden 20F (11C) drop in water temperatures down to freezing levels west of longitude 48 30' W, it is clear that the Labrador Current was dominant in that region back in April in 1912 causing all those icebergs and pack ice to drift unexpectedly far to the south, reaching as far south as 41 16' N as documented by the SS Carpathia. It is also probable that the general current flow coming down from the Labrador would have looped around in a counter clockwise direction into a northeasterly flow similar to that shown in the satellite radar image.

 

 

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