What is the rationale behind PASTFACT?
The unknown impacts of a warmer and wetter future Arctic
The future Arctic
Warmer but also wetter
While it is widely known that the Arctic warms more rapidly than anywhere else on our planet, it is far less known that the region is also getting wetter. The amount of precipitation may increase by a staggering 50% by 2100 AD.
Linked to sea ice loss
Enhances moisture fluxes
The intensification of the Arctic hydrological cycle is mainly driven by one of the most visible impacts of climate change: the dramatic decline of the region`s sea ice cover. As larger parts of a warmer Arctic Ocean remain ice-free longer, far more moisture moves to the atmosphere by evaporation.
Major uncertainties
The amount and phase of future precipitation is poorly constrained
The near-future trajectory of these changes is highly uncertain as climate models do not agree on the magnitude of precipitation, or if it will fall as snow or rain.
Global consequences
Ice melt-driven sea-level rise offset by more snowfall
A wetter future Arctic will have global consequences as changes in the amount of snowfall could counteract temperature-driven melt of the region`s glaciers. These are and will remain major contributors to global sea-level rise.
How can we better constrain Arctic change?
Opening a unique past window into a warmer wetter Future Arctic
Early Holocene
Most recent past period of warmer-than-present conditions
The uncertainty of model predictions is largely caused by poor baseline data: observations from the Arctic are scarce. In addition, future change will exceed what we`ve experienced. To provide more robust constraints, PASTFACT will target geological archives from the warmer-than-present Early Holocene period, which lasted from around 12 to 8 thousand years ago. Recent work shows that Arctic warming during this period equaled that of mid-range scenarios for 2100 AD.
Lake sediments
First-class recorders of past climate
Year after year, materials accumulate in lake basins, layer by layer. Sediment sequences from these basins thus represent first-class records of past change. A few meters of mud may cover thousands of years. The chemical, biological and physical properties of these sediments record climate conditions during the time of deposition. In PASTFACT, we try to apply a range of new methods to extract this information with unmatched precision.
Arctic climate change hotspots
Northeast Svalbard and Greenland
PASTFACT will retrieve lake sediments from two areas that uniquely sensitive to the amplified response of the Arctic climate system - northeast Svalbard and Greenland. To be able study the interplay between warmer, wetter conditions and glacier change, we will target sites where there is evidence that glaciers survived Early Holocene warming.
What will be done in PASTFACT?
Applying a toolbox of new methods that is greater than the sum of its parts
Seasonality
Will the fraction of snowfall change?
Using past precipitation isotopes recorded by plant leaf waxes, and analyzing these compounds in settings fed by different water sources, PASTFACT will disentangle the seasonality of precipitation change under warmer-than-present conditions.
Temperature
How are warming & wetting linked?
Using the temperature-sensitivity of fat saturation in fossil algae, PASTFACT will assess the relationship between warming and wetting in the Arctic.
Glaciers
Can snowfall offset melt?
To reconstruct the response of glaciers to warmer wetter conditions, PASTFACT will rely on new remote-sensing products and medical scanning techniques to link transitions between glacigenic and non-glacial sedimentation to the exact position of the Early Holocene ice margin.
Models
Can we reconcile simulated and reconstructed change?
To lift PASTFACT beyond the sum of its proxy data, reconstructions will be interfaced with models to simulate the values of climate parameters that can not easily be derived from proxy data - notably precipitation.
