The ice streams were broadly stable up until 2009, since when they have been losing on the order of 56 billion tonnes of ice a year to the ocean.
Warm waters from the deep sea may be driving the changes, the UK-based team says.
The details of the satellite research are published in Science Magazine.
They include more than 10 years of space observations of a broad swathe of coastline roughly 750km in length, on the south-western sector of the peninsula.
Here there is a multitude of glaciers slipping down mountainous terrain and terminating in the Bellingshausen Sea.
"Around 2009/2010, the surface in this part of the southern Antarctic Peninsula started to lower at a really quite dramatic rate, of 4m per year in some places. That's a pretty big signal," said Bristol's Prof Jonathan Bamber.
"The total loss of ice per year is about 60 cubic km. Just to put that into some kind of context: 4 cubic km is roughly equivalent to the domestic water supply of the UK every year."
Antarctica's contribution to sea level rise from melting ice, although growing, is still less than 0.5mm per year. The reported behaviour, however, would mean the south-western peninsula sector now has the second biggest input to that contribution behind the large glaciers that drain into the Amundsen Sea even further to the south and west.
One of the key elements of the new study was the use of the European Space Agency's Cryosat platform, which circles the Earth at a height of over 700km.
This satellite has a remarkable radar altimeter that measures the shape of the ice surface below, and this instrument can be tuned to see rugged regions like the peninsula with a previously unobtainable resolution.
For a check on its work, the Bristol team also used a completely different type of measurement from the US space agency's Grace satellites. This pair of platforms senses the Earth's gravity field and can, in a coarse way, calculate how much ice mass has been lost from a particular region of the continent. These observations are said to be in good agreement with the altimetry data.
The scientists say the Antarctic climate models indicate no significant changes in snowfall or air temperature over the study period, which leads them to think the rapid ice loss is the result of warmer ocean waters.
