The Greenland ice sheet is crucial to global climate as it stores 3 million cubic km of water in the ice. Its melting, causing sea level rise, could be a tipping point.
Forecasts
With the increase in greenhouse gas emissions, Greenland ice sheet will contribute 50cm to global sea level rise by 2100. Coast stations have been detecting rising temperatures for years. However, the impact of global warming on the ice cap at high altitudes (up to 3,000 m) was unclear due to poor long-term observation.
Lo studio “Modern temperatures in central–north Greenland warmest in past millennium”
Lo studio “Modern temperatures in central-north Greenland warmest in past millennium” published in Nature, conducted by a team of researchers from the Alfred-Wegener-Institut, Helmholtz-Zentrum für Polar- und Meeresforschung and Niels Bohr Institutet from Københavns Universitet, used a series of ice cores of exceptional length and quality to reconstruct the temperature of the last 1,000 years. It turns out that warming in north-central Greenland is surprisingly high, with the most recent decade (2001-2011) it was the hottest in 1,000 years and the region is now 1.5°C warmer than in the 20th century. The study shows that the effects of global warming have reached even the remote and high-elevation areas of north-central Greenland.
The study of the composition of isotopes
The study’s lead glaciologist analyzed the isotopic composition of shallow ice cores in north-central Greenland and found that the time series continuously spans more than 1,000 years (1000 to 2011). These data show that 2001-2011 warming is very different from natural variations over the past 1,000 years and surprised at the noticeable difference due to global warming.
How the analyzes were done
The recent temperature study in north-central Greenland used a series of ice cores of unprecedented length and quality to reconstruct the temperature over the past 1,000 years. These data indicate that today’s warming is surprisingly pronounced and that the region is now 1.5°C warmer than it was in the 20th century. The composition of the isotopes in the ice cores indicates that the warming in 2001-2011 clearly differs from the natural variations of the last 1,000 years. Previous ice cores did not indicate clear warming in the region due to natural climate variability and uncertainties in the assessment of natural variability. The research team consistently used a single method to measure stable oxygen isotope concentrations within the ice, reducing the uncertainties in assessing natural variability.
Analysis of melting ice
The German and Danish researchers also analyzed the melting ice sheet in Greenland. It appears that melt has increased considerably in recent years and is now contributing significantly to global sea level rise. The lead author of the study says that core temperature is closely related to meltwater melt across Greenlandwhich occurs along the edge of the ice sheet near the coast.
The interweaving of data
The authors used data from a regional climate model and satellite observations to quantify the connection between temperatures in high-elevation areas and melting along the edges of the ice sheet. This allowed them to convert the temperature changes identified in the ice cores into melting rates and provide estimates for the last 1,000 years. This is considered an important dataset for climate research, as greater understanding of ice sheet melt dynamics improves projections of future sea level rise and reduces uncertainties in projections.
Comparison with climate change in the Arctic
The study authors found that the climate of the Greenland ice sheet is largely decoupled from the rest of the Arctic and that its conditions are not well represented by Arctic representations globally. Their temperature reconstruction in central Greenland showed that the latter has its own dynamics and is affected differently by atmospheric circulation patterns than other parts of the Arctic. The need for regionally resolved time series over the Arctic was therefore highlighted to reliably describe climate change in the Arctic.
Antarctica is also experiencing climate change with ice sheet shrinkage reaching its lowest levels ever last year.
