Model and state dependence of the atmospheric response to Arctic sea-ice loss

The climate response to Arctic sea-ice loss is highly uncertain. There exists considerable disagreement between observational and modelling studies, and between models, for reasons that remain poorly understood. To make progress, the Polar Amplification Model Intercomparison Project (PAMIP) was designed to provide coordinated experiments, with consistent sea-ice loss applied in multiple models. Results from the PAMIP are presented, focussing on the robustness of the atmospheric response to Arctic sea-ice loss across models and, within individual models, the dependence of the response on the mean state.In the troposphere, the mid-latitude jet is either weakened and/or shifted towards the equator in all models, albeit with varying magnitudes. We hypothesise that the magnitude of the jet response is sensitive to the atmospheric model resolution. To test this, and to more broadly identify the aspects of the atmospheric response that are sensitive to model resolution, we compare like-for-like experiments with two versions of the HadGEM3 model at low (N96) and high (N216) horizontal resolution.The stratospheric polar vortex response to Arctic sea-ice loss is not consistent between models, and appears to be influenced by both the size of the ensemble for each model and the phase of the Quasi-Biennial Oscillation (QBO). The possible modulating effect of the QBO is further explored using new simulations with background atmospheric states representing the easterly and westerly QBO phases.A surprising early result from the PAMIP simulations were sizeable changes in the Southern Hemisphere in response to Arctic sea-ice loss and significant changes in the Northern Hemisphere in response to Antarctic sea-ice loss, even in atmosphere-only model experiments. The robustness of such apparent interhemispheric connections across models, ensemble sizes and mean states is investigated.&#160;&#160;&#160;

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Role of the internal climate variability in the atmospheric response to a sudden summer Arctic sea ice loss

10.5194/egusphere-egu21-2528 ◽

2021 ◽

Author(s):

Steve Delhaye ◽

Thierry Fichefet ◽

François Massonnet ◽

David Docquier ◽

Christopher Roberts ◽

...

Keyword(s):

Climate Variability ◽

Sea Ice ◽

Signal To Noise Ratio ◽

Horizontal Resolution ◽

Arctic Sea Ice ◽

Atmospheric Response ◽

Signal To Noise ◽

Internal Climate Variability ◽

Arctic Sea ◽

Arctic Sea Ice Loss

The retreat of Arctic sea ice for the last four decades is a primary manifestation of the climate system response to increasing atmospheric greenhouse gas concentrations. This retreat is frequently considered as a possible driver of atmospheric circulation anomalies at mid-latitudes. However, the year-to-year evolution of the Arctic sea ice cover is also characterized by significant fluctuations attributed to internal climate variability. It is unclear how the atmosphere will respond to a near-total retreat of summer Arctic sea ice, a reality that might occur in the foreseeable future. This study uses sensitivity experiments&#160; with higher and lower horizontal resolution configurations of three global coupled climate models to investigate the local and remote atmospheric responses to a reduction in Arctic sea ice cover during the preceding summer. Recognizing that these responses likely depend on the model itself and on its horizontal resolution, and that the model&#8217;s internally-generated climate variability may obscure the atmospheric response, we design a protocol to compare each source separately. After imposing a 15-month albedo perturbation resulting in a sudden summer Arctic sea ice loss, the remote mid-latitude climate response has a very low signal-to-noise ratio such that internal climate variability dominates the uncertainty of the response, regardless of the atmospheric variable. Indeed, more than 28, 165 and 210 members are needed to detect a robust response in surface air temperature, precipitation and sea level pressure to sea ice loss in Europe, respectively. Finally, we find that horizontal resolution plays a secondary role in the uncertainty of the atmospheric response to substantial perturbation of Arctic sea ice. These findings suggest that even with higher resolution model configurations, it is important to have large ensemble sizes to increase the signal to noise ratio for the mid-latitude atmospheric response to sea ice changes.

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Isolating the Atmospheric Circulation Response to Arctic Sea Ice Loss in the Coupled Climate System

Journal of Climate ◽

10.1175/jcli-d-16-0257.1 ◽

2017 ◽

Vol 30 (6) ◽

pp. 2163-2185 ◽

Cited By ~ 54

Author(s):

Russell Blackport ◽

Paul J. Kushner

Keyword(s):

Sea Ice ◽

Polar Vortex ◽

Arctic Sea Ice ◽

Low Latitude ◽

Stratospheric Polar Vortex ◽

Sea Level Pressure ◽

Surface Warming ◽

Arctic Sea ◽

Pressure Anomaly ◽

Arctic Sea Ice Loss

Abstract In this study, coupled ocean–atmosphere–land–sea ice Earth system model (ESM) simulations driven separately by sea ice albedo reduction and by projected greenhouse-dominated radiative forcing are combined to cleanly isolate the sea ice loss response of the atmospheric circulation. A pattern scaling approach is proposed in which the local multidecadal mean atmospheric response is assumed to be separately proportional to the total sea ice loss and to the total low-latitude ocean surface warming. The proposed approach estimates the response to Arctic sea ice loss with low-latitude ocean temperatures fixed and vice versa. The sea ice response includes a high northern latitude easterly zonal wind response, an equatorward shift of the eddy-driven jet, a weakening of the stratospheric polar vortex, an anticyclonic sea level pressure anomaly over coastal Eurasia, a cyclonic sea level pressure anomaly over the North Pacific, and increased wintertime precipitation over the west coast of North America. Many of these responses are opposed by the response to low-latitude surface warming with sea ice fixed. However, both sea ice loss and low-latitude surface warming act in concert to reduce subseasonal temperature variability throughout the middle and high latitudes. The responses are similar in two related versions of the National Center for Atmospheric Research Earth system models, apart from the stratospheric polar vortex response. Evidence is presented that internal variability can easily contaminate the estimates if not enough independent climate states are used to construct them.

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Weak Stratospheric Polar Vortex Events Modulated by the Arctic Sea‐Ice Loss

Journal of Geophysical Research Atmospheres ◽

10.1029/2018jd029222 ◽

2019 ◽

Vol 124 (2) ◽

pp. 858-869 ◽

Cited By ~ 8

Author(s):

Kazuhira Hoshi ◽

Jinro Ukita ◽

Meiji Honda ◽

Tetsu Nakamura ◽

Koji Yamazaki ◽

...

Keyword(s):

Sea Ice ◽

Polar Vortex ◽

Arctic Sea Ice ◽

The Arctic ◽

Stratospheric Polar Vortex ◽

Arctic Sea ◽

Arctic Sea Ice Loss

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Weakening of the stratospheric polar vortex by Arctic sea-ice loss

Nature Communications ◽

10.1038/ncomms5646 ◽

2014 ◽

Vol 5 (1) ◽

Cited By ~ 304

Author(s):

Baek-Min Kim ◽

Seok-Woo Son ◽

Seung-Ki Min ◽

Jee-Hoon Jeong ◽

Seong-Joong Kim ◽

...

Keyword(s):

Sea Ice ◽

Polar Vortex ◽

Arctic Sea Ice ◽

Stratospheric Polar Vortex ◽

Arctic Sea ◽

Arctic Sea Ice Loss

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How Robust is the Atmospheric Response to Projected Arctic Sea Ice Loss Across Climate Models?

Geophysical Research Letters ◽

10.1029/2019gl084936 ◽

2019 ◽

Vol 46 (20) ◽

pp. 11406-11415 ◽

Cited By ~ 6

Author(s):

J. A. Screen ◽

R. Blackport

Keyword(s):

Sea Ice ◽

Climate Models ◽

Arctic Sea Ice ◽

Atmospheric Response ◽

Arctic Sea ◽

Arctic Sea Ice Loss

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Simulated Atmospheric Response to Regional and Pan-Arctic Sea Ice Loss

Journal of Climate ◽

10.1175/jcli-d-16-0197.1 ◽

2017 ◽

Vol 30 (11) ◽

pp. 3945-3962 ◽

Cited By ~ 74

Author(s):

James A. Screen

Keyword(s):

Sea Ice ◽

General Circulation ◽

Large Scale ◽

Circulation Model ◽

Arctic Sea Ice ◽

Ecological Impacts ◽

The Arctic ◽

Stratospheric Polar Vortex ◽

Arctic Sea ◽

Arctic Sea Ice Loss

Abstract The loss of Arctic sea ice is already having profound environmental, societal, and ecological impacts locally. A highly uncertain area of scientific research, however, is whether such Arctic change has a tangible effect on weather and climate at lower latitudes. There is emerging evidence that the geographical location of sea ice loss is critically important in determining the large-scale atmospheric circulation response and associated midlatitude impacts. However, such regional dependencies have not been explored in a thorough and systematic manner. To make progress on this issue, this study analyzes ensemble simulations with an atmospheric general circulation model prescribed with sea ice loss separately in nine regions of the Arctic, to elucidate the distinct responses to regional sea ice loss. The results suggest that in some regions, sea ice loss triggers large-scale dynamical responses, whereas in other regions sea ice loss induces only local thermodynamical changes. Sea ice loss in the Barents–Kara Seas is unique in driving a weakening of the stratospheric polar vortex, followed in time by a tropospheric circulation response that resembles the North Atlantic Oscillation. For October–March, the largest spatial-scale responses are driven by sea ice loss in the Barents–Kara Seas and the Sea of Okhotsk; however, different regions assume greater importance in other seasons. The atmosphere responds very differently to regional sea ice losses than to pan-Arctic sea ice loss, and the response to pan-Arctic sea ice loss cannot be obtained by the linear addition of the responses to regional sea ice losses. The results imply that diversity in past studies of the simulated response to Arctic sea ice loss can be partly explained by the different spatial patterns of sea ice loss imposed.

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Are 100 ensemble members enough to capture the remote atmospheric response to +2°C Arctic sea ice loss ?

Journal of Climate ◽

10.1175/jcli-d-20-0613.1 ◽

2021 ◽

pp. 1-54

Author(s):

Y. Peings ◽

Z. Labe ◽

G. Magnusdottir

Keyword(s):

Sea Ice ◽

General Circulation ◽

Internal Variability ◽

General Circulation Models ◽

Arctic Sea Ice ◽

Model Assessment ◽

Atmospheric Response ◽

Arctic Sea ◽

Ocean Atmosphere ◽

Arctic Sea Ice Loss

AbstractThis study presents results from the Polar Amplification Multimodel Intercomparison Project (PAMIP) single-year time-slice experiments that aim to isolate the atmospheric response to Arctic sea ice loss at global warming levels of +2°C. Using two General Circulation Models (GCMs), the ensemble size is increased up to 300 ensemble members, beyond the recommended 100 members. After partitioning the response in groups of 100-ensemble members, the reproducibility of the results is evaluated, with a focus on the response of the mid-latitude jet streams in the North Atlantic and North Pacific. Both atmosphere-only and coupled ocean-atmosphere PAMIP experiments are analyzed. Substantial differences in the mid-latitude response are found among the different experiment subsets, suggesting that 100-member ensembles are still significantly influenced by internal variability, which can mislead conclusions. Despite an overall stronger response, the coupled ocean-atmosphere runs exhibit greater spread due to additional ENSO-related internal variability when the ocean is interactive. The lack of consistency in the response is true for anomalies that are statistically significant according to Student’s-t and False Discovery Rate tests. This is problematic for the multi-model assessment of the response, as some of the spread may be attributed to different model sensitivities while it is due to internal variability. We propose a method to overcome this consistency issue, that allows for more robust conclusions when only 100 ensemble members are used.

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Mechanisms of Stratospheric and Tropospheric Circulation Response to Projected Arctic Sea Ice Loss*

Journal of Climate ◽

10.1175/jcli-d-15-0169.1 ◽

2015 ◽

Vol 28 (19) ◽

pp. 7824-7845 ◽

Cited By ~ 122

Author(s):

Lantao Sun ◽

Clara Deser ◽

Robert A. Tomas

Keyword(s):

Sea Ice ◽

Polar Vortex ◽

Arctic Sea Ice ◽

Climate Impacts ◽

Negative Phase ◽

Surface Boundary ◽

Arctic Sea ◽

Tropospheric Circulation ◽

Arctic Sea Ice Loss ◽

The Impact

Abstract The impact of projected Arctic sea ice loss on the atmospheric circulation is investigated using the Whole Atmosphere Community Climate Model (WACCM), a model with a well-resolved stratosphere. Two 160-yr simulations are conducted: one with surface boundary conditions fixed at late twentieth-century values and the other with identical conditions except for Arctic sea ice, which is prescribed at late twenty-first-century values. Their difference isolates the impact of future Arctic sea ice loss upon the atmosphere. The tropospheric circulation response to the imposed ice loss resembles the negative phase of the northern annular mode, with the largest amplitude in winter, while the less well-known stratospheric response transitions from a slight weakening of the polar vortex in winter to a strengthening of the vortex in spring. The lack of a significant winter stratospheric circulation response is shown to be a consequence of largely cancelling effects from sea ice loss in the Atlantic and Pacific sectors, which drive opposite-signed changes in upward wave propagation from the troposphere to the stratosphere. Identical experiments conducted with Community Atmosphere Model, version 4, WACCM’s low-top counterpart, show a weaker tropospheric response and a different stratospheric response compared to WACCM. An additional WACCM experiment in which the imposed ice loss is limited to August–November reveals that autumn ice loss weakens the stratospheric polar vortex in January, followed by a small but significant tropospheric response in late winter and early spring that resembles the negative phase of the North Atlantic Oscillation, with attendant surface climate impacts.

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