Environmental scientists, led by the UK's University of Birmingham and the University of Leeds, found that glaciers ending in lakes are generally much larger and account for over three per cent of the world's glaciers but lost 134 billion tonnes of ice annually between 2000 and 2019.
Since these together cover more than half of the world's glacier area, their melting has caused more than half of total glacier ice loss.
The findings, published in the journal Nature Communications, also showed that lake- and ocean-ending glaciers flow on average 10 per cent and 44 per cent faster than those ending on land, respectively, and lake-ending glaciers lose around 57 per cent more ice than land-ending glaciers, relative to their size.
"Glaciers ending in lakes really stand out -- they're losing ice particularly quickly. We don't yet know exactly why. It could be the lakes themselves, the size and shape of the glaciers, or a bit of both. Untangling that is the next big question, especially as glacier lakes are becoming more common in a warming climate," said author Joseph Mallalieu.
The researchers explained that lakes can affect glaciers in ways that may contribute to a higher ice loss.
Lake-ending glaciers can lose large chunks of ice from the glacier front as icebergs, a process known as calving, and lake water can melt the ice below the waterline, both helping to speed up ice loss, they said.
Models used for projecting glacier change do not yet fully account for glaciers ending in lakes, the researchers said.
The team's new glacier classification could help address this, enabling other researchers to improve projections of sea-level rise, water resources and natural hazards, they said.
The authors "show that although lake-, marine- and shelf-terminating glaciers comprise only 3.2 per cent of glaciers globally, they account for over half of global glacier area and mass loss."
Lake-ending glaciers were found to be present in every major glacier regions worldwide, and, in most regions, lost ice faster than glaciers ending on land or in oceans.
Further, a growing number of glaciers are changing type as the climate warms -- ocean-ending glaciers are retreating onto land in parts of the Arctic, while worldwide, the growth of glacier lakes is turning some land-ending glaciers into lake-ending ones, the study found.
The study's results suggest the shifts could have contrasting effects, with glaciers retreating onto land likely to slow down, while those newly ending in lakes could lose ice faster.
"Our findings underscore the need for improved representation of non-land glacier termini in models of glacier evolution and sea-level rise, and suggest that distinguishing the environmental and geometric controls of termini on glacier dynamics remains an important challenge for future research," the authors wrote.