Thwaites glacier front in the vulnerable West Antarctica sector is very broad (70 miles wide where it meets the ocean) and, in its entirety, is the size of Florida. The glacier is the most feared as it decays rapidly and threatens coastal cities worldwide. The cork in the bottle for the entirety of West Antarctica holds ten feet of sea level rise. The collapse of the marine extension will not add to sea level rise as it already floats. When it collapses, the cork pops, and the land ice is free to slide into the Weddel Sea and the Amundsen Sea, raising sea levels.
All the damage to Thwaites’s stability is occurring below the ice. The upwelling of warm ocean water softens and erodes the soft white underbelly of the glacier. The upwelling also lifts the ice, where warmer waters can flow to the ridges and beyond the grounding line, furthering the ice’s decay with a faster flow, more shattering and fracturing with the threat of collapse. The water can do that because the ice is no longer anchored on the bedrock.
The ocean at the front of the glacier is still quite cold, approximately 34-36 degrees Fahrenheit. That is above freezing, and if you think of your afternoon cocktail filled with ice, that is similar to the temperature of the ocean water eating away at the glacier. Sipping your cocktail, you observe that the ice is melting, which is precisely what is occurring to the underside of the massive marine extension of Thwaites glacier. The glacier by itself holds two feet of sea level rise.
Geophysicists were able to map the front of the glacier’s seafloor. Like you and me, we have a history, and so does Thwaites.
A recent study by the University of South Florida:
At some point in the last 200 years, over a duration of less than six months, the front of glacier lost contact with a seabed ridge and retreated at a rate of more than 2.1 kilometers per year (1.3 miles per year) — twice the rate documented using satellites between 2011 and 2019.
“Our results suggest that pulses of very rapid retreat have occurred at Thwaites Glacier in the last two centuries, and possibly as recently as the mid-20th Century,” said Graham.
“Thwaites is really holding on today by its fingernails, and we should expect to see big changes over small timescales in the future – even from one year to the next – once the glacier retreats beyond a shallow ridge in its bed,” said marine geophysicist and study co-author, Robert Larter, from the British Antarctic Survey.
The tongue of Thwaites is fifty miles wide. You can make a distinction on the tongue depending on its stability and whether it is anchored on a ridge. While in peril, the western part of the tongue is still relatively stable. The eastern part is shedding chunks of ice like there is no tomorrow, and the eastern side also holds the majority of land ice. Sooner rather than later for chaos, in my estimation.
For twenty-two years, a significant iceberg named Iceberg B22a broke from the Thwaites’ tongue in 2001 and became stuck at its front, protecting the remaining ice from the open ocean. The iceberg was fifty-three miles long and forty miles wide. It, too, is subjected to warming waters, and the berg thinned enough that it was freed from the mount it was stuck on in September of 2022. That means a brutal assault on Thwaites from the ocean will occur. A flotilla of icebergs calving from the front is expected following the iceberg exiting the Amundsen Sea and entering the Weddel. If you did not know, West Antarctica passed the tipping point many years ago.
