By Sam Hume
An international team led by the British Antarctic Survey has built the most detailed picture yet of the hidden land that lies under Antarctica’s ice. The dataset, called Bedmap3, stitches together more than six decades of measurements from aircraft, satellites, ships, and even dog-drawn sleds to reveal the continent as if its ice had been lifted away. If all of Antarctica’s ice melted, global sea level would rise by about 190 feet (58m).
The new map is far sharper than previous versions. It has a resolution of about a third of a mile (500m), and fills major gaps in places such as East Antarctica, the South Pole region, the Antarctic Peninsula, parts of West Antarctica, and the Transantarctic Mountains. Bedmap3 assembles 82 million data points, including from previous Bedmap surveys, and adds fresh aerial data. Where direct readings were sparse, the team used well tested methods to estimate ice thickness, for example by modeling how ice flows around rock outcrops when the ice is thin.
This map has also provided results to buttress our understanding of basic statistics on the southern continent’s ice sheet. Antarctica holds about 6.5 million cubic miles (27 million km3) of ice. Spread across about 5.26 million square miles (13.63 million km2), that ice averages 6,391 feet thick (1,948m). Excluding the floating ice shelves, the average thickness rises to about 7,047 feet (2,148m). This has also led to a better understanding of the region’s extremes.
Several headline findings stand out. The thickest ice is no longer thought to be in the Astrolabe Basin in Adélie Land. Bedmap3 shifts the record to an unnamed canyon in Wilkes Land at 76.052° S, 118.378° E, where the ice is over 15,603 feet (4,757m) thick. The outlines of deep valleys and subglacial troughs are much clearer, and the locations of mountains that poke through the ice are better mapped. The project also refines the position of grounding lines, the places where ice that rests on land first begins to float as an ice shelf at the coast. These boundaries are crucial because ocean water can flow under floating ice and speed up melt.
As lead author Dr. Hamish Pritchard explains, ice spreads across the land like syrup poured over a bumpy cake. Ridges can slow this flow, while hollows actually let ice move faster. This flow pattern influences how Antarctica will respond to a warmer climate. The new map suggests the ice sheet is thicker than once thought and that more of it sits on bedrock below sea level. That geometry can make more of the ice vulnerable to warm ocean water as it seeps beneath it. Recent estimates of ice loss vary by method and time span, but they agree that Antarctica is shedding mass at a significant rate each year, which adds to sea level rise.
Bedmap3 is also a community effort. It builds on earlier projects from 2001 and 2013, widens international data sharing under FAIR data principles, and provides an open web portal so scientists can both reproduce the gridding and create custom products. This makes Bedmap3 a sharper foundation for the computer models that forecast how Antarctica’s ice will change. Better knowledge of the bed beneath the ice leads to better predictions of the future above it. It also provides us with a look at the mysterious land hidden deep beneath the continent.
References:
Nature
British Antarctic Survey