Can regional climate engineering save the summer Arctic sea ice? (original) (raw)
Mitigation implications of an ice-free summer in the Arctic Ocean
Earth's Future, 2017
The rapid loss of sea ice in the Arctic is one of the most striking manifestations of climate change. As sea ice melts, more open water is exposed to solar radiation, absorbing heat and generating a sea ice-albedo feedback that reinforces Arctic warming. Recent studies stress the significance of this feedback mechanism and suggest that ice-free summer conditions in the Arctic Ocean may occur faster than previously expected, even under low-emissions pathways. Here, we use an integrated assessment model to explore the implications of a potentially rapid sea ice-loss process. We consider a scenario leading to a full month free of sea ice in September 2050, followed by three potential scenarios afterward: partial recovery, stabilization, and continued loss of sea ice. We analyze how these scenarios affect the mitigation efforts to keep global temperature increase below 2 ∘ C. Our results show that sea-ice melting in the Arctic requires more stringent mitigation efforts globally. We find that global CO 2 emissions would need to reach zero levels 5-15 years earlier and that the carbon budget would need to be reduced by 20-51% to offset this additional source of warming. The extra mitigation effort would imply an 18-59% higher mitigation cost to society. Our results also show that to achieve the 1.5 ∘ C target in the presence of ice-free summers, negative emissions would be needed. This study highlights the need for a better understanding of how the rapid changes observed in the Arctic may impact our society. Since satellite data records began in 1978, Arctic sea-ice extent has been showing persistent and significant reductions across all months. Generally, this decrease has been most pronounced for the month of September, at the end of the melting season. In September 2012, when the last record minimum was registered, Arctic sea-ice extent was 3.3 × 10 6 km 2 , equivalent to a 50% reduction compared to the sea-ice cover during the early 1980s. On average, Arctic sea-ice extent declined at a rate of 7.5% per decade in the period 1979-2001 and at 22.2% per decade within the period 2001-2015 [ARC, 2015]. The retreat in the extent of sea ice is part of an ongoing, more abrupt decline in ice thickness, volume, and age [ARC, 2015].
Climate Dynamics, 2012
The atmospheric general circulation model EC-EARTH-IFS has been applied to investigate the influence of both a reduced and a removed Arctic sea ice cover on the Arctic energy budget and on the climate of the Northern mid-latitudes. Three 40-year simulations driven by original and modified ERA-40 sea surface temperatures and sea ice concentrations have been performed at T255L62 resolution, corresponding to 79 km horizontal resolution. Simulated changes between sensitivity and reference experiments are most pronounced over the Arctic itself where the reduced or removed sea ice leads to strongly increased upward heat and longwave radiation fluxes and precipitation in winter. In summer, the most pronounced change is the stronger absorption of shortwave radiation which is enhanced by optically thinner clouds. Averaged over the year and over the area north of 70°N, the negative energy imbalance at the top of the atmosphere decreases by about 10 W/m 2 in both sensitivity experiments. The energy transport across 70°N is reduced. Changes are not restricted to the Arctic. Less extreme cold events and less precipitation are simulated in sub-Arctic and Northern midlatitude regions in winter.
FROZEN ARCTIC: Compendium of interventions to slow down, halt, and reverse the effects of climate change in the Arctic and northern regions A University of the Arctic Rapid Response Assessment, 2023
Sea Ice Growth Management (an assessment in Compendium of interventions to slow down, halt, and reverse the effects of climate change in the Arctic and northern regions). pp. 36-37. FROZEN ARCTIC: Compendium of interventions to slow down, halt, and reverse the effects of climate change in the Arctic and northern regions A University of the Arctic Rapid Response Assessment Keywords: Arctic, nature-based approaches, climate engineering, geoengineering, climate action, cryosphere Recommended Citation: van Wijngaarden, A., Alfthan, B., Moore, J., Kullerud, L., Kurvits, T., Mulelid, O., and Husabø, E. 2023. Compendium to the University of the Arctic Rapid Response Assessment: Frozen Arctic. UArctic, GRIDArendal, and Arctic Centre/University of Lapland. https://doi.org/10.5281/zenodo.8408608 This compendium supports the report Frozen Arctic: Horizon scan of interventions to slow down, halt, and reverse the effects of climate change in the Arctic and northern regions, available electronically at www.grida.no/publications and uarctic.org/publications, and the submitted article A survey of interventions to actively conserve the frozen North Funding: This report was developed under Phase I of the Frozen Arctic Conservation project and was supported by Global Affairs Canada through the Global Arctic Leadership Initiative. frozen-arctic-rra-compendium.pdf 195 pages. This compendium supports the report Frozen Arctic: Horizon scan of interventions to slow down, halt, and reverse the effects of climate change in the Arctic and northern regions, available electronically at www.grida.no/publications and uarctic.org/publications, and the submitted article A survey of interventions to actively conserve the frozen North This compendium provides some assessment on Sea Ice Growth Management (geoengineering) technique which I have proposed in the past. Use citation as suggested by the authors as enclosed. (Thank you).
Earth's Future Mitigation implications of an ice-free summer in the Arctic Ocean
The rapid loss of sea ice in the Arctic is one of the most striking manifestations of climate change. As sea ice melts, more open water is exposed to solar radiation, absorbing heat and generating a sea ice–albedo feedback that reinforces Arctic warming. Recent studies stress the significance of this feedback mechanism and suggest that ice-free summer conditions in the Arctic Ocean may occur faster than previously expected, even under low-emissions pathways. Here, we use an integrated assessment model to explore the implications of a potentially rapid sea ice-loss process. We consider a scenario leading to a full month free of sea ice in September 2050, followed by three potential scenarios afterward: partial recovery, stabilization, and continued loss of sea ice. We analyze how these scenarios affect the mitigation efforts to keep global temperature increase below 2 ∘ C. Our results show that sea-ice melting in the Arctic requires more stringent mitigation efforts globally. We find that global CO 2 emissions would need to reach zero levels 5–15 years earlier and that the carbon budget would need to be reduced by 20–51% to offset this additional source of warming. The extra mitigation effort would imply an 18–59% higher mitigation cost to society. Our results also show that to achieve the 1.5 ∘ C target in the presence of ice-free summers, negative emissions would be needed. This study highlights the need for a better understanding of how the rapid changes observed in the Arctic may impact our society.
Geophysical Research Letters, 2010
1] Numerical experiments are conducted to project arctic sea ice responses to varying levels of future anthropogenic warming and climate variability over 2010-2050. A summer ice-free Arctic Ocean is likely by the mid-2040s if arctic surface air temperature (SAT) increases 4°C by 2050 and climate variability is similar to the past relatively warm two decades. If such a SAT increase is reduced by one-half or if a future Arctic experiences a range of SAT fluctuation similar to the past five decades, a summer ice-free Arctic Ocean would be unlikely before 2050. If SAT increases 4°C by 2050, summer ice volume decreases to very low levels (10-37% of the 1978-2009 summer mean) as early as 2025 and remains low in the following years, while summer ice extent continues to fluctuate annually. Summer ice volume may be more sensitive to warming while summer ice extent more sensitive to climate variability. The rate of annual mean ice volume decrease relaxes approaching 2050. This is because, while increasing SAT increases summer ice melt, a thinner ice cover increases winter ice growth. A thinner ice cover also results in a reduced ice export, which helps to further slow ice volume loss. Because of enhanced winter ice growth, arctic winter ice extent remains nearly stable and therefore appears to be a less sensitive climate indicator. Citation: Zhang, J., M. Steele, and A. Schweiger (2010), Arctic sea ice response to atmospheric forcings with varying levels of anthropogenic warming and climate variability, Geophys.
A sea ice free summer Arctic within 30 years
Geophysical Research Letters, 2009
as the second sequential year with an extreme summer Arctic sea ice extent minimum. Although such a sea ice loss was not indicated until much later in the century in the Intergovernmental Panel on Climate Change 4th Assessment Report, many models show an accelerating decline in the summer minimum sea ice extent during the 21st century. Using the observed 2007/2008 September sea ice extents as a starting point, we predict an expected value for a nearly sea ice free Arctic in September by the year 2037. The first quartile of the distribution for the timing of September sea ice loss will be reached by 2028. Our analysis is based on projections from six IPCC models, selected subject to an observational constraints. Uncertainty in the timing of a sea ice free Arctic in September is determined based on both within-model contributions from natural variability and between-model differences.
On the Potential for Abrupt Arctic Winter Sea Ice Loss
Journal of Climate, 2016
The authors examine the transition from a seasonally ice-covered Arctic to an Arctic Ocean that is sea ice free all year round under increasing atmospheric CO2 levels. It is shown that in comprehensive climate models, such loss of Arctic winter sea ice area is faster than the preceding loss of summer sea ice area for the same rate of warming. In two of the models, several million square kilometers of winter sea ice are lost within only one decade. It is shown that neither surface albedo nor cloud feedbacks can explain the rapid winter ice loss in the climate model MPI-ESM by suppressing both feedbacks in the model. The authors argue that the large sensitivity of winter sea ice area in the models is caused by the asymmetry between melting and freezing: an ice-free summer requires the complete melt of even the thickest sea ice, which is why the perennial ice coverage decreases only gradually as more and more of the thinner ice melts away. In winter, however, sea ice areal coverage rem...
Annual Review of Earth and Planetary Sciences, 2012
Arctic sea ice is a key indicator of the state of global climate because of both its sensitivity to warming and its role in amplifying climate change. Accelerated melting of the perennial sea ice cover has occurred since the late 1990s, which is important to the pan-Arctic region, through effects on atmospheric and oceanic circulations, the Greenland ice sheet, snow cover, permafrost, and vegetation. Such changes could have significant ramifications for global sea level, the ocean thermohaline circulation, native coastal communities, and commercial activities, as well as effects on the global surface energy and moisture budgets, atmospheric and oceanic circulations, and geosphere-biosphere feedbacks. However, a system-level understanding of critical Arctic processes and feedbacks is still lacking. To better understand the past and present states and estimate future trajectories of Arctic sea ice and climate, we argue that it is critical to advance hierarchical regional climate model...
Springtime atmospheric energy transport and the control of Arctic summer sea-ice extent
2013
The summer sea-ice extent in the Arctic has decreased in recent decades, a feature that has become one of the most distinct signals of the continuing climate change 1-4 . However, the interannual variability is large-the ice extent by the end of the summer varies by several million square kilometres from year to year 5 . The underlying processes driving this year-to-year variability are not well understood. Here we demonstrate that the greenhouse effect associated with clouds and water vapour in spring is crucial for the development of the sea ice during the subsequent months. In years where the end-of-summer sea-ice extent is well below normal, a significantly enhanced transport of humid air is evident during spring into the region where the ice retreat is encountered. This enhanced transport of humid air leads to an anomalous convergence of humidity, and to an increase of the cloudiness. The increase of the cloudiness and humidity results in an enhancement of the greenhouse effect. As a result, downward long-wave radiation at the surface is larger than usual in spring, which enhances the ice melt. In addition, the increase of clouds causes an increase of the reflection of incoming solar radiation. This leads to the counterintuitive effect: for years with little sea ice in September, the downwelling short-wave radiation at the surface is smaller than usual. That is, the downwelling short-wave radiation is not responsible for the initiation of the ice anomaly but acts as an amplifying feedback once the melt is started.