Uncertainty in climate model projections of Arctic sea ice decline: An evaluation relevant to polar bears

2007 ◽  
pp. 1-41 ◽  
Author(s):  
Eric DeWeaver
2021 ◽  
Author(s):  
Svenya Chripko ◽  
Rym Msadek ◽  
Emilia Sanchez-Gomez ◽  
Laurent Terray ◽  
Laurent Bessières ◽  
...  

<p>Previous climate model studies have shown that Arctic sea ice decline can solely affect weather and climate at lower latitudes during the cold season. However, the mechanisms beneath this linkage are poorly understood. Whether sea ice loss have had an influence on the lower latitudes climate over the past decades is also uncertain (Barnes and Screen 2015). The goal of this work is to better understand the relative contributions of dyncamical and thermodynamical changes in the atmospheric response to Arctic sea ice loss, which have been suggested to oppose each other (Screen 2017). We conducted two sets of sensitivity transient experiments that allow to isolate the effect of Arctic sea ice decline on the mid-latitudes from other climate forcings, using the climate model CNRM-CM6 (Voldoire et al. 2019) in a coupled configuration or with an atmosphere-only. The first set of experiments, that is part of the European H2020 PRIMAVERA project, consists of a 100-member ensemble in which sea ice albedo is reduced to the ocean value (PERT) in the fully coupled CNRM-CM6, and which is compared to a 1950 control run (CTL) (Haarsma et al. 2016). This yields idealised ice-free conditions in summer and a more moderate sea ice reduction during the following months. The second set of experiments, that is part of the CMIP6 Polar Amplification Model Intercomparison Project (PAMIP, Smith et al. 2019), consists of a 300-member ensemble in which the atmospheric component of CNRM-CM6 is forced by sea ice anomalies associated with a future 2°C warming (FUT) and present day sea surface temperatures (SSTs). These are compared to experiments in which the atmosphere is forced by present-day sea ice conditions (PD) and the same SSTs. To extract the dynamical component of the response in the two sets of experiments, we use a dynamical adjustment method (Deser et al. 2016) based on a regional reconstruction of circulation analogs. We focus on three mid-latitudes regions in which a significant near-surface temperature response has been identified, namely North America, Europe and central Asia. We show that the cooling occurring over central Asia in both sets of experiments is dynamically-induced through an intensification of the Siberian High, and that opposed temperature responses over North America between the two sets of experiments could be explained by opposed dynamical components occurring in response to the imposed Arctic sea ice decline. Finally, we discuss whether different dynamical and thermodynamical contributions in the PAMIP multi-model experiments could explain the multi-model differences in the atmospheric response to sea ice loss.</p>


2021 ◽  
Author(s):  
Harry Heorton ◽  
Michel Tsamados ◽  
Paul Holland ◽  
Jack Landy

<p><span>We combine satellite-derived observations of sea ice concentration, drift, and thickness to provide the first observational decomposition of the dynamic (advection/divergence) and thermodynamic (melt/growth) drivers of wintertime Arctic sea ice volume change. Ten winter growth seasons are analyzed over the CryoSat-2 period between October 2010 and April 2020. Sensitivity to several observational products is performed to provide an estimated uncertainty of the budget calculations. The total thermodynamic ice volume growth and dynamic ice losses are calculated with marked seasonal, inter-annual and regional variations</span><span>. Ice growth is fastest during Autumn, in the Marginal Seas and over first year ice</span><span>. Our budget decomposition methodology can help diagnose the processes confounding climate model predictions of sea ice. We make our product and code available to the community in monthly pan-Arctic netcdft files for the entire October 2010 to April 2020 period.</span></p>


2021 ◽  
Author(s):  
David Lipson ◽  
Kim Reasor ◽  
Kååre Sikuaq Erickson

<p>In this project we analyze artwork and recorded statements of 5<sup>th</sup> grade students from the community of Utqiaġvik, Alaska, who participated in a science-art outreach activity. The team consisted of a scientist (Lipson), an artist (Reasor) and an outreach specialist (Erickson) of Inupiat heritage from a village in Alaska. We worked with four 5th grade classes of about 25 students each at Fred Ipalook Elementary. The predominantly Inupiat people of Utqiaġvik are among those who will be most impacted by climate change and the loss of Arctic sea ice in the near future. Subsistence hunting of marine mammals associated with sea ice is central to the Inupiat way of life. Furthermore, their coastal homes and infrastructure are increasingly subject to damage from increased wave action on ice-free Beaufort and Chukchi Seas. While the people of this region are among the most directly vulnerable to climate change, the teachers reported that the subject is not generally covered in the elementary school curriculum.</p><p>The scientist and the local outreach specialist gave a short presentation about sea ice and climate change in the Arctic, with emphasis on local impacts to hunting and infrastructure. We then showed the students a large poster of historical and projected sea ice decline, and asked the students to help us fill in the white space beneath the lines. The artist led the children in making small paintings that represent things that are important to their lives in Utqiaġvik (they were encouraged to paint animals, but they were free to do whatever they wanted). We returned to the class later that week and had each student briefly introduce themselves and their painting, and place it on the large graph of sea ice decline, which included the dire predictions of the RCP8.5 scenario. Then we added the more hopeful RCP2.6 scenario to end on a positive note.</p><p>Common themes expressed in the students’ artwork included subsistence hunting, other aspects of traditional Inupiat culture, nature and family. Modern themes such as sports and Pokémon were also common. The students reacted to the topic of climate change with pictures of whales, polar bears and other animals, and captions such as “Save the world/ice/animals.” There were several paintings showing unsuccessful hunts for whales or seals. Some students displayed an understanding of ecosystem science in their recorded statements. For example, a student who painted the sun and another who painted a krill both succinctly described energy flow in food webs that support the production of whales (for example, “I drew krill because without krill there wouldn’t be whales”). Some of the students described the consequences of sea ice loss to local wildlife with devastating succinctness (sea ice is disappearing and polar bears will go extinct). The overall sense was that the children had a strong grasp of the potential consequences of climate change to their region and way of life.</p>


2019 ◽  
Vol 32 (5) ◽  
pp. 1361-1380 ◽  
Author(s):  
J. Ono ◽  
H. Tatebe ◽  
Y. Komuro

Abstract The mechanisms for and predictability of a drastic reduction in the Arctic sea ice extent (SIE) are investigated using the Model for Interdisciplinary Research on Climate (MIROC) version 5.2. Here, a control (CTRL) with forcing fixed at year 2000 levels and perfect-model ensemble prediction (PRED) experiments are conducted. In CTRL, three (model years 51, 56, and 57) drastic SIE reductions occur during a 200-yr-long integration. In year 56, the sea ice moves offshore in association with a positive phase of the summer Arctic dipole anomaly (ADA) index and melts due to heat input through the increased open water area, and the SIE drastically decreases. This provides the preconditioning for the lowest SIE in year 57 when the Arctic Ocean interior is in a warm state and the spring sea ice volume has a large negative anomaly due to drastic ice reduction in the previous year. Although the ADA is one of the key mechanisms behind sea ice reduction, it does not always cause a drastic reduction. Our analysis suggests that wind direction favoring offshore ice motion is a more important factor for drastic ice reduction events. In years experiencing drastic ice reduction events, the September SIE can be skillfully predicted in PRED started from July, but not from April. This is because the forecast errors for the July sea level pressure and those for the sea ice concentration and sea ice thickness along the ice edge are large in PRED started from April.


2017 ◽  
Author(s):  
Jamie G. L. Rae ◽  
Alexander D. Todd ◽  
Edward W. Blockley ◽  
Jeff K. Ridley

Abstract. This paper presents an analysis of Arctic summer cyclones in a climate model and in a reanalysis dataset. A cyclone identification and tracking algorithm is run for output from model simulations at two resolutions, and for the reanalysis, using two different tracking variables (mean sea-level pressure and 850 hPa vorticity) for identification of the cyclones. Correlations between characteristics of the cyclones and September Arctic sea ice extent are investigated, and the influence of the tracking variable, the spatial resolution of the model, and spatial and temporal sampling, on the correlations is explored. We conclude that the correlations obtained depend on all of these factors, and that care should be taken when interpreting the results of such analyses, especially when the focus is on one reanalysis, or output from one model, analysed with a single tracking variable for a short time period.


2019 ◽  
Author(s):  
Yufei Zou ◽  
Yuhang Wang ◽  
Zuowei Xie ◽  
Hailong Wang ◽  
Philip J. Rasch

Abstract. Recent studies suggested significant impacts of boreal cryosphere changes on wintertime air stagnation and haze pollution extremes in China. However, the underlying mechanism of such a teleconnection relationship remains unclear. Here we used the Whole Atmosphere Community Climate Model (WACCM) to investigate dynamic processes leading to atmospheric circulation and air stagnation responses to Arctic sea ice changes. We conducted four climate sensitivity experiments by perturbing sea ice concentrations (SIC) and corresponding sea surface temperature (SST) in autumn and early winter over the whole Arctic and three sub-regions in the climate model. The results indicate different responses in the general circulation and regional ventilation to the region-specific Arctic changes, with the largest increase of both the probability (by 120 %) and the intensity (by 32 %) of air stagnation extreme events being found in the experiment driven by SIC and SST changes over the Pacific sector of the Arctic (the East Siberian and Chukchi Seas). The increased air stagnation extreme events are mainly driven by an amplified hemispheric-scale atmospheric teleconnection pattern that resembles the negative phase of the Eurasian (EU) pattern. Dynamical diagnostics suggest that convergence of transient eddy forcing in the vicinity of Scandinavia in winter is largely responsible for the amplification of the teleconnection pattern. Transient eddy vorticity fluxes dominate the transient eddy forcing and produce a barotropic anticyclonic anomaly near Scandinavia and wave-train propagation across Eurasia to the downstream regions in East Asia. The piecewise potential vorticity inversion analysis reveals that this long-range atmospheric teleconnection of the Arctic origin takes place primarily in the middle and upper troposphere. The anomalous ridge over East Asia in the middle and upper troposphere worsens regional ventilation conditions by weakening monsoon northwesterlies and enhancing temperature inversion near the surface, leading to more and stronger air stagnation and pollution extremes over eastern China in winter. Ensemble projections based on the state-of-the-art climate models in the Coupled Model Intercomparison Project Phase 6 (CMIP6) corroborate this teleconnection relationship between high-latitude environmental changes and middle-latitude weather extremes, though the tendency and magnitude vary considerably among each participating model.


2021 ◽  
Author(s):  
Kristian Strommen ◽  
Stephan Juricke

Abstract. The extent to which interannual variability in Arctic sea ice influences the midlatitude circulation has been extensively debated. While observational data supports the existence of a teleconnection between November sea ice in the Barents-Kara region and the subsequent winter circulation, climate models do not consistently reproduce such a link, with only very weak inter-model consensus. We show, using the EC-Earth3 climate model, that while a deterministic ensemble of coupled simulations shows no evidence of such a teleconnection, the inclusion of stochastic parameterizations to the ocean and sea ice component of EC-Earth3 results in the emergence of a robust teleconnection comparable in magnitude to that observed. We show that this can be accounted for entirely by an improved ice-ocean-atmosphere coupling due to the stochastic perturbations. In particular, the inconsistent signal in existing climate model studies may be due to model biases in surface coupling, with stochastic parameterizations being one possible remedy.


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