The tragedy of the "unsinkable" Titanic - lost in the cold water of the Atlantic - became part of history and pop culture, but the story of the main culprit that caused the disaster is mostly forgotten and only vague descriptions and some photos exists of the supposed iceberg(s). One famous photography taken from board of the cable ship "Minia", one of the first ships to reach the area in search for debris and bodies, shows a tabular iceberg, an unusual shape for icebergs in the northern Atlantic. The crew found debris and bodies floating in the vicinity and the captain assured that this was the only iceberg near the point of the collision. However most surviving Titanic testimonies described later the infamous iceberg with a prominent peak or even two.
Fig.1. One of the many icebergs photographed in the morning of April 15, 1912. The passengers on the ship "Prinz Adalbert", still unaware of the disaster of the previous night, reported later to have noted a "red smear" at the waterline of the white iceberg (image in public domain).
Fig.2. Another iceberg, photographed five days later from board of the German ship "Bremen", claimed to be the Titanic iceberg based on the vicinity to the location of the disaster and the description of the iceberg according to survivors (image in public domain). An authentic photography of the iceberg that sank the "unsinkable" Titanic was worth lot of money for the eager press.
Fig.3. Photography taken from board of the ship "Birma" of the same iceberg as seen by the passengers of the "Carpathia" - the first ship to approach the scene of the disaster and save the surviving passengers of the Titanic - and published at the time in the "Daily Sketch". This iceberg has in fact some remarkable similarities to the iceberg as described by survivors of the disaster (image in public domain).
Despite the question if one of the photos shows really the culprit iceberg, the remarkably number of spotted icebergs emphasizes the notion that in 1912 a quite impressive number of these white titans reached such southern latitudes.
The icebergs encountered in the North Atlantic originate mainly from the western coasts of Greenland, where ice streams deliver large quantities of ice in the fjords which lead to the Baffin Bay. Every year ten thousand of small and large pieces of ice drop from the front of the glaciers and are pushed by the West Greenland Current slowly to northern latitudes, far away from ship routes. Following first the coast of Greenland this current is diverted by the Canadian coast to the south, forming the Labrador Current that circumnavigates Newfoundland and delivers the iceberg to the warm Gulf Stream. A more than 5.000 km long journey full of obstacles and incessant erosion by the sun, the water and the waves. Only estimated 1 to 2% of large icebergs will, after a period of 1-3 years, reach latitude 45°N, crossing one of the most important route for ships of the entire Atlantic Ocean.
Fig.4. Schematic diagram of marine currents (blue= cold; red = hot) around Greenland, probable region of origin (West Greenland) and hypothetical trajectory of the iceberg that sank the Titanic.
Apparently in 1912 icebergs were spotted remarkably often in this region and various hypotheses tried to explain this "anomaly". The years before 1912 were characterized by mild winters in Europe and possibly the northern Atlantic. It was therefore speculated that the (relative) warm temperatures increased the melting rate and activity of the calving glaciers on Greenland. Also a strengthened Labrador Current, pushing cold water and icebergs much more to the south, was proposed to explain the ice field that in the cold night 100 years ago forced various ships to stop along the Atlantic route. Both hypotheses are based on the recorded values of Sea Surface Temperature (see this diagram by the Woods Hole Oceanographic Institution), which show an alternation of a warm and cold period in 1900-1920.
A recent hypothesis - promoted by NG - proposes that an exceptional high tide prevented much of the larger icebergs to run aground along the coasts of the Baffin Bay and the Labrador Sea. However considering that this tide occurred just some months before (January 1912) and the average velocity of an iceberg is low (0,7km/h~0,6mph), the Titanic iceberg had to take a straight course to arrive in time for his rendezvous with history - April 14, 1912, at 23:40.
Based on iceberg counts along the shores of Labrador and later in the Atlantic, also the year 1912 don't seem to be necessarily such an anomalous event, but the disaster raised considerably the interest (and maybe perception) of the public for icebergs.
Fig.5. Iceberg counts (estimated before 1912) at 48°N, data compiled from the International Ice Patrol Iceberg Database.
In the days after the disaster bypassing ships encountered and photographed various icebergs. Some eyewitnesses claim to have noted red paint on some of them; however there is no conclusive evidence that one of these spotted white giants is really the iceberg that sank the Titanic. At least some weeks later the culprit iceberg, captured by the warm water of the Gulf Stream, melted and disappeared forever into the Atlantic Ocean.
EATON, J.P. & HAAS, C.A. (1986): Titanic Triumph and Tragedy. Haynes Publishing: 352
SOUTH, C. et al. (2006): The Iceberg That Sank the Titanic. The Natural World documentary film - BBC