Hooker Lake, New Zealand (2016). Photo credit: Jenna Sutherland
Meltwater lakes that form at the edges of glaciers cause the ice to recede much further and faster compared to glaciers that end on land, according to a new study. The authors of the study warn, however, that the effects of these glacial lakes are not shown in current ice loss models.
Therefore, estimates of recession rates and ice mass loss from sea-terminated glaciers are likely to be underestimated in the coming decades.
Many mountain glaciers today end in such lakes, which are formed when meltwater is trapped behind glacier remains. They are known as proglacial lakes. Climate change has increased glacier melt worldwide, which in turn has led to a dramatic increase in the size and number of proglacial lakes. Little is known about the effects of proglacial lakes on de-icing rates and glacier behavior.
Hooker Lake, New Zealand (2018). Photo credit: Jenna Sutherland
Now, for the first time, an international team of researchers led by the University of Leeds has quantified the influence of proglacial lakes on mountain glaciers using computer simulations. They found that the presence of a proglacial lake causes a glacier to recede more than four times further and accelerate ice flow up to eight times compared to the same glacier ending on land under the same climate.
The results were published today (October 9, 2020) in the journal Geophysical research letters, show that it took a land-ending glacier 1000 years to succumb to the same recession as a sea-ending glacier experienced in 100 years.
The study director Dr. Jenna Sutherland did this research as a PhD student at the School of Geography in Leeds. She said, “An ice cube in a bowl of water melts much faster than an ice cube on a table, and the effects of the proglacial lakes on the glacial ice are about the same.
“The simulations show that the influence of a proglacial lake on a glacier predominantly takes place over decades to centuries and not thousands of years, which means that the glacier is retreating much faster than ever before due to climatic changes alone.”
Lake Tasman, New Zealand (2016). Photo credit: Jenna Sutherland
The study co-author, Dr. Jonathan Carrivick, Lecturer in Geomorphology at Leeds, said, “Our results suggest that simulations of past, contemporary or future glaciers ignore the effects of ice-contact lakes and are likely to misrepresent the timing and speed of the recession, particularly the timing and speed changes that will occur as soon as a proglacial lake forms.
“These effects need to be incorporated into all future models and simulations in order to obtain an accurate global picture of glacier ice loss.”
The team used the BISICLES ice flow model to analyze the effects of a proglacial on the Pukaki Glacier in New Zealand during the recession from the end of the last ice age.
Study co-author James Shulmeister of the University of Canterbury, New Zealand said, “While this study focused on New Zealand, proglacial lakes are widespread during global glacier retreat, and so this paper should be of global interest and concern. ”
He also noted: “This study is also critical because the time of ice retreat is often used to determine the synchronicity or absence of ice events around the world. Important conclusions were drawn about the role of phenomena such as oceanic circulation in influencing the global climate system due to glacier retreat times. If the timings are wrong, the relationship between these processes may need to be re-examined. ”
Reference: “Proglacial Lakes Control Glacier Geometry and Behavior During Recession” by JL Sutherland, JL Carrivick, N. Gandy, J. Shulmeister, DJ Quincey and SL Cornford, September 21, 2020, Geophysical research letters.
DOI: 10.1029 / 2020GL088865
