Causes and impacts of Greenland atmospheric Blocking changes
Lead Research Organisation:
UNIVERSITY OF LINCOLN
Abstract
This project aims to provide a major advance in the understanding of the causes of atmospheric circulation changes (specifically changes in blocking or persistent high air pressure) over Greenland, their relation to variations in the North Atlantic atmospheric and oceanic circulation systems, their consequences for climate change and extreme weather conditions over Greenland and the wider North Atlantic/Northwest Europe/UK region, and their impacts on Greenland Ice Sheet mass loss and global sea-level rise.
High-pressure blocking in Northern Hemisphere mid-high latitudes is an important feature of the general circulation of the atmosphere that is closely linked to the jet stream and extreme weather events over densely populated mid-latitude regions. The physical causes of blocking and consequently how it responds to and influences broader-scale climate change are poorly understood, especially in terms of connecting weather (daily) and climate (year-to-year or longer) timescales. Recent research shows a significant increase in blocking over the Greenland region, mainly in summer, since around 1990. This is not well simulated by currently available global climate models. This deficiency may be linked to recent rapid Arctic sea-ice loss which is also not well captured by the climate models. However, the latest generation of climate models show some improvement compared with earlier versions, although still have some differences between modelled and observed representations of Greenland Blocking.
Our proposal addresses this model-observation mismatch by means of a comprehensive comparison using new methods, the updated observations and the latest state-of-the-art climate model simulations. We seek to understand the causes of changes in Greenland Blocking through observation-based data on a wide range of timescales from daily to decadal, analysing how changes in extreme Greenland Blocking events are linked to climatological variations and trends, and considering fundamental physical causes (heating and/or atmospheric circulation changes) of extreme Greenland Blocking events. Natural variability is an important aspect of blocking, and the recent significant trend in Greenland Blocking in summer is the time of year when changes in Atlantic-wide sea-surface temperatures - called Atlantic Multidecadal Variability - are most closely associated with melt and runoff changes from the Greenland Ice Sheet. We will therefore compare climate-model output from models with varying representations of the ocean and sea ice in order to identify possible oceanic and/or Arctic sea-ice loss influences on Greenland Blocking changes.
There would be profound implications of a continued increase in Greenland Blocking in summer over the coming decades: for example, enhancing melting and mass loss of the Greenland Ice Sheet. Recent results indicate a non-linear, accelerating response of the ice sheet's surface melt and runoff to rising temperatures where the latter are partly linked with the recent blocking increase in summer. Crucially, understanding how the Greenland Ice Sheet responds to future climate change, and the resulting effects on global sea-level rise, depends upon being able to better model atmospheric circulation changes over the Greenland region. Therefore, we will use our insights gained from earlier work in the project and novel climate model experiments to evaluate the likely impacts of future Greenland Blocking changes on North Atlantic and European weather and climate, and on the Greenland Ice Sheet mass balance and hence global sea-level rise. We expect that our results from this climatically crucial part of the North Atlantic will provide a major step forward for understanding the causes and impacts of Greenland Blocking and help guide development of the next generation of global climate models.
High-pressure blocking in Northern Hemisphere mid-high latitudes is an important feature of the general circulation of the atmosphere that is closely linked to the jet stream and extreme weather events over densely populated mid-latitude regions. The physical causes of blocking and consequently how it responds to and influences broader-scale climate change are poorly understood, especially in terms of connecting weather (daily) and climate (year-to-year or longer) timescales. Recent research shows a significant increase in blocking over the Greenland region, mainly in summer, since around 1990. This is not well simulated by currently available global climate models. This deficiency may be linked to recent rapid Arctic sea-ice loss which is also not well captured by the climate models. However, the latest generation of climate models show some improvement compared with earlier versions, although still have some differences between modelled and observed representations of Greenland Blocking.
Our proposal addresses this model-observation mismatch by means of a comprehensive comparison using new methods, the updated observations and the latest state-of-the-art climate model simulations. We seek to understand the causes of changes in Greenland Blocking through observation-based data on a wide range of timescales from daily to decadal, analysing how changes in extreme Greenland Blocking events are linked to climatological variations and trends, and considering fundamental physical causes (heating and/or atmospheric circulation changes) of extreme Greenland Blocking events. Natural variability is an important aspect of blocking, and the recent significant trend in Greenland Blocking in summer is the time of year when changes in Atlantic-wide sea-surface temperatures - called Atlantic Multidecadal Variability - are most closely associated with melt and runoff changes from the Greenland Ice Sheet. We will therefore compare climate-model output from models with varying representations of the ocean and sea ice in order to identify possible oceanic and/or Arctic sea-ice loss influences on Greenland Blocking changes.
There would be profound implications of a continued increase in Greenland Blocking in summer over the coming decades: for example, enhancing melting and mass loss of the Greenland Ice Sheet. Recent results indicate a non-linear, accelerating response of the ice sheet's surface melt and runoff to rising temperatures where the latter are partly linked with the recent blocking increase in summer. Crucially, understanding how the Greenland Ice Sheet responds to future climate change, and the resulting effects on global sea-level rise, depends upon being able to better model atmospheric circulation changes over the Greenland region. Therefore, we will use our insights gained from earlier work in the project and novel climate model experiments to evaluate the likely impacts of future Greenland Blocking changes on North Atlantic and European weather and climate, and on the Greenland Ice Sheet mass balance and hence global sea-level rise. We expect that our results from this climatically crucial part of the North Atlantic will provide a major step forward for understanding the causes and impacts of Greenland Blocking and help guide development of the next generation of global climate models.
Publications
Cottrell F
(2024)
Signal-to-noise errors in free-running atmospheric simulations and their dependence on model resolution
in Atmospheric Science Letters
Hanna E
(2024)
Short- and long-term variability of the Antarctic and Greenland ice sheets
in Nature Reviews Earth & Environment
Luu L
(2024)
Greenland summer blocking characteristics: an evaluation of a high-resolution multi-model ensemble
in Climate Dynamics
Maddison J
(2024)
Missing Increase in Summer Greenland Blocking in Climate Models
in Geophysical Research Letters
Wei H
(2024)
Predicting the Atlantic Meridional Overturning Circulation Using Nonlinear System Identification Methods and the NARMAX Model
in Inzynieria Mineralna
| Description | (1) An increasing trend in summertime atmospheric blocking over Greenland was observed during the early twenty-first century. However, this trend is not reproduced in climate models. This may have important implication for climate change projections, as summertime Greenland blocking drives the melting of its ice sheet which is a major contributing factor to global sea level rise. Here, recent trends in Greenland blocking are assessed in nearly 500 ensemble members from a large archive of state-of-the-art climate models. We found that a recent increasing trend like that observed is absent in all of the ensemble members, and a trend of such magnitude is very unlikely to be simulated in them, which suggests a deficiency in the climate model simulation of Greenland blocking. The model simulations do however suggest that Greenland blocking is partly forced by sea surface temperatures/sea ice concentrations and/or anthropogenic aerosols, but the response of the models to these forcings may be too weak. These results provide new understanding on drivers of Greenland blocking in climate models and offer avenues for model development designed to improve simulations of Greenland climate. (2) We found that the High Resolution Model Intercomparison Project (HiResMIP) global climate model ensemble can reproduce the spatial pattern of Greenland blocking events, albeit with systematic biases, and capture the relative frequencies of the main blocking patterns: namely the wave breaking structure, North Atlantic ridge, and omega-type blocking. However, the HighResMIP ensemble fails to simulate the observed temporal variations of Greenland blocking index (GB2) and the extremely high values of daily GB2 observed in recent decades. In addition, we do not find clearly superior representation of blocking features from higher-resolution in HighResMIP models compared with lower-resolution models. We also find large sea surface temperature biases over the North Atlantic and seas surrounding Greenland, and biases in moisture transport over the North Atlantic toward Greenland, especially over the western flank of blocking areas, which might together contribute to model biases in the representation of blocking magnitude. |
| Exploitation Route | Methods of analysing global climate model data can be applied to other research projects on jet-stream analysis, for example. |
| Sectors | Energy Environment |