When discussing this interesting question, it should always be kept in mind that Captain Smith's decisions were based on his very considerable knowledge of the routes in question and the normal behaviour of the sea ice in early April.
Captain Smith had warnings of ice on his track some 135 miles to the west of
The Corner. He had written in the Order Book that the ship was to be turned onto her final course for New York at 5-50pm that evening. This meant that he thought
Titanic would be in the vicinity of the position where the ice was reported to have been at around midnight...15 hours after the time when it was last seen.
Under normal circumstances.. i.e. a prevailing weather system from the SW and NE trending currents, he probably decided that the ice would be about 30 miles to the north and eastward of his expected position when
Titanic crossed the 50th meridian.
The sea temperatures recorded by the SS
Californian in the vicinity of
The Corner on the same day suggested that the extension of The Gulf Stream was transporting surface water to the north of the 42nd parallel. The sea temperature reading taken on board
Titanic when in the same area that Sunday afternoon would have been similar and would have reinforced Smiths estimates of ice movement.
All these assessments would have been made by him during the early afternoon of April 14. Unfortunately. he had no idea that a High Pressure area was building and that the wind would drop away after 6 pm. This would allow Titanic to achieve her optimum speed at for engine revolutions of 75 rpm. My best guess is that she made a knot faster that the speed used by Smith in his calculation and consequently, she was up to the ice area earlier than expected and the ice had stopped moving.
Captain Smiths's main concern was small ice... not icebergs. So far south as that, sea ice is more influenced by wind than by current. Such ice can only be detected in time if the tell-tale breaking waves round its waterline are seen in time. Smith and Lightoller knew this and had taken the normal precautions.
As for reducing speed; The
Carpathia was making about 14 knots and the
Californian was making 11 knots yet the former, even with much enhanced lookouts, had just enough time to avoid the berg that did for Titanic. The latter did not see the ice in time and actually entered the fringes of the pack before her bow was swung clear.
In my early days, there was a mantra that was dinned into us...
"When considering actions to be taken, always have due regard for the circumstances of each case" In my opinion, Smith did nothing more than follow that mantra to the best of his ability.
Jim C.