Melting sea ice increases Arctic precipitation, complicates climate predictions

December 21, 2015

HANOVER, N.H. - The melting of sea ice will significantly increase Arctic precipitation, creating a climate feedback comparable to doubling global carbon dioxide, a Dartmouth College-led study finds.

"The increases of precipitation and changes in the energy balance may create significant uncertainty in climate predictions," says lead author Ben Kopec, a PhD candidate in Dartmouth's Department of Earth Sciences.

The findings appear in the journal Proceedings of the National Academy of Sciences. A PDF is available on request.

Global climate is influenced by the Arctic water cycle, which is partly regulated by sea ice through its control on evaporation and precipitation. There is a growing consensus among scientists that a decrease in sea ice would increase Arctic precipitation because of increased evaporation. Direct measurement of precipitation is difficult in the Arctic because of its cold, windy environments, so the quantitative link between precipitation and sea ice is poorly understood.

In their study, the Dartmouth-led team quantified that link by measuring the hydrogen and oxygen isotopic compositions of precipitation from 1990 to 2012 at six sites across the Arctic. They then used these empirically established sensitivities of precipitation isotopes to sea ice change to project future precipitation changes and to evaluate impacts of these changes on the energy balance. Their approach is based on the premise that Arctic precipitation is composed mostly of water from two marine evaporation regions, or "moisture sources" - one subtropical and one local - and that the relative contributions of the two sources to the precipitation can be determined from the stable isotopic ratios of the precipitation.

They found that for a sea ice extent decrease of 100,000 km2 - or 38,610 square miles -- the percentage of Arctic sourced moisture increases by 18.2 percent and 10.8 percent, respectively, in the Canadian Arctic and Greenland Sea regions. This corresponds to increases of 10.9 percent and 2.7 percent per degree Celsius of Arctic warming, respectively.

The researchers reached no conclusion on whether the increased precipitation will fall as snow or rain. If it falls as snow, it could potentially increase glacial mass and the number of days of high land surface reflectivity, thus having a cooling effect. But if the increased precipitation falls as rain, it would cause earlier spring melt and/or later onset of autumn snow coverage, a longer low reflectivity period and additional warming. In either case, the resulting radiative forcing likely has an order of magnitude similar to that of the forcing from doubling carbon dioxide, thus demonstrating that the sea ice feedback to radiation balance through the Arctic water cycle is potentially a major component of climate change.

"Sea ice is declining at an alarming rate, so it is important to understand the consequences of the climate feedbacks caused by these changes," Kopec says. "We show that the loss of sea ice will likely increase precipitation, which will impact communities and ecosystems around the Arctic. The change of precipitation, depending on the seasonal distribution, may impact the energy balance on the same order of magnitude as the feedbacks associated with doubling carbon dioxide."
-end-
The study was supported by the National Science Foundation for the iisPACS (Isotopic Investigation of Sea ice and Precipitation in the Arctic Climate System) and for Dartmouth's IGERT (Integrative Graduate Education and Research Traineeship) project for Polar Environmental Change.

Ben Kopec is available to comment at Ben.G.Kopec.GR@dartmouth.edu.

Broadcast studios: Dartmouth has TV and radio studios available for interviews. For more information, visit: http://communications.dartmouth.edu/media/broadcast-studios

Dartmouth College

Related Climate Change Articles from Brightsurf:

Are climate scientists being too cautious when linking extreme weather to climate change?
Climate science has focused on avoiding false alarms when linking extreme events to climate change.

Mysterious climate change
New research findings underline the crucial role that sea ice throughout the Southern Ocean played for atmospheric CO2 in times of rapid climate change in the past.

Mapping the path of climate change
Predicting a major transition, such as climate change, is extremely difficult, but the probabilistic framework developed by the authors is the first step in identifying the path between a shift in two environmental states.

Small change for climate change: Time to increase research funding to save the world
A new study shows that there is a huge disproportion in the level of funding for social science research into the greatest challenge in combating global warming -- how to get individuals and societies to overcome ingrained human habits to make the changes necessary to mitigate climate change.

Sub-national 'climate clubs' could offer key to combating climate change
'Climate clubs' offering membership for sub-national states, in addition to just countries, could speed up progress towards a globally harmonized climate change policy, which in turn offers a way to achieve stronger climate policies in all countries.

Review of Chinese atmospheric science research over the past 70 years: Climate and climate change
Over the past 70 years since the foundation of the People's Republic of China, Chinese scientists have made great contributions to various fields in the research of atmospheric sciences, which attracted worldwide attention.

A CERN for climate change
In a Perspective article appearing in this week's Proceedings of the National Academy of Sciences, Tim Palmer (Oxford University), and Bjorn Stevens (Max Planck Society), critically reflect on the present state of Earth system modelling.

Fairy-wrens change breeding habits to cope with climate change
Warmer temperatures linked to climate change are having a big impact on the breeding habits of one of Australia's most recognisable bird species, according to researchers at The Australian National University (ANU).

Believing in climate change doesn't mean you are preparing for climate change, study finds
Notre Dame researchers found that although coastal homeowners may perceive a worsening of climate change-related hazards, these attitudes are largely unrelated to a homeowner's expectations of actual home damage.

Older forests resist change -- climate change, that is
Older forests in eastern North America are less vulnerable to climate change than younger forests, particularly for carbon storage, timber production, and biodiversity, new research finds.

Read More: Climate Change News and Climate Change Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.