Iceberg risk in theTitanicyear of 1912: was it exceptional?

Abstract

At 2340h local time (0310 GMT) on the cold, moonless, night of 14 April 1912, near 41°47 N, 49°55 W (Marine Accident Investigation Branch, 1992), the crow’s nest lookouts on board RMS Titanic sighted a large iceberg only 500m ahead. Despite quick action on the bridge to slow the ship, and turn to port, as well as the closing of the water-tight doors, the slow response of a large vessel meant that the iceberg still struck the ship aft of the bows. Some 100m of her hull below the waterline buckled, allowing water to flood into the ship across several compartments (Howells, 1992). In little more than two and a half hours she had sunk, with the loss of 1514 lives (Havern, 2012). A distress call requesting assistance was transmitted only 20 minutes after the collision, and RMS Carpathia turned and raced towards the Titanic at a speed of 17.5kn, 20% above her normal maximum speed. However, she did not arrive at the scene until around 0330h (15 April; 0700 GMT), by which time only 710 people remained to be rescued from the 20 lifeboats that had been able to be launched (Howells, 1992). The weather, ice conditions and time of year combined to increase the iceberg hazard on that fateful day. High pressure had dominated the mid-latitude, central Atlantic for several days (Howells, 1992) and by the time of the collision a ridge linking two high-pressure centres over Nova Scotia and the south of Ireland extended across the entire Atlantic (Figure 1). This resulted in northnorthwest winds transporting nearfreezing air from northeast Canada over the western Atlantic south of Newfoundland (Figure 1). These winds and temperatures, assisted by the prevailing southward flow of the ocean’s Labrador Current on the Grand Banks, led to transport of icebergs and sea ice further south than is currently normal for the time of year, but not beyond the known limits to icebergs during the twentieth century (Figure 2). However, note that Figure 2. The average sea-ice limit for April 1979–2013 (dotted), a typical Newfoundland maximum sea-ice limit for the early twentieth century (dashed and denoted as 1912; from Hill and Jones, 1990) and the maximum iceberg limit for 1900–2000 are shown, in addition to the 48°N line. The location of the Titanic is shown by an ‘X’. The blue shading shows depth, with the lightest blue denoting the continental shelf (<100m depth). Figure 1. Sea-level pressure and air-temperature chart for 0000 GMT, 15 April 1912, taken from the ensemble mean of the twentieth century reanalysis (Compo et al., 2011). The location of the Titanic is shown by an ‘X’.