Mechanisms for low-frequency variability of summer Arctic sea ice extent

Zhang, Rong

doi:10.1073/pnas.1422296112

Cited by 190 publications

(212 citation statements)

References 52 publications

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“…this including Kay et al (2011), Day et al (2012, Notz and Marotzke (2012), Stroeve et al (2012), Notz (2015), Swart et al (2015) and Zhang (2015). We are also cautious of overfitting; applying a trend correction would potentially result in an over-confident projection.…”

Section: Bias Correction Methodologymentioning

confidence: 99%

Improved Arctic sea ice thickness projections using bias-corrected CMIP5 simulations

2015

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Abstract. Projections of Arctic sea ice thickness (SIT) have the potential to inform stakeholders about accessibility to the region, but are currently rather uncertain. The latest suite of CMIP5 global climate models (GCMs) produce a wide range of simulated SIT in the historical period and exhibit various biases when compared with the Pan-Arctic Ice-Ocean Modelling and Assimilation System (PIOMAS) sea ice reanalysis. We present a new method to constrain such GCM simulations of SIT via a statistical bias correction technique. The bias correction successfully constrains the spatial SIT distribution and temporal variability in the CMIP5 projections whilst retaining the climatic fluctuations from individual ensemble members. The bias correction acts to reduce the spread in projections of SIT and reveals the significant contributions of climate internal variability in the first half of the century and of scenario uncertainty from the mid-century onwards. The projected date of ice-free conditions in the Arctic under the RCP8.5 high emission scenario occurs in the 2050s, which is a decade earlier than without the bias correction, with potentially significant implications for stakeholders in the Arctic such as the shipping industry. The bias correction methodology developed could be similarly applied to other variables to reduce spread in climate projections more generally.

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Section: Bias Correction Methodologymentioning

confidence: 99%

Improved Arctic sea ice thickness projections using bias-corrected CMIP5 simulations

2015

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“…For individual years like 2007, sea ice divergence is found to be an important factor (Hutchings and Perovich, 2015), while the influence from atmospheric and oceanic heat transport is further discussed below. Using coupled climate model simulations, Zhang (2015) identified the northward Atlantic heat transport, Pacific heat transport, and the spring AD as the main predictors of lowfrequency variability of summer Arctic SIE. The study focused on variability longer than 30 years and used a 3600-year segment of the preindustrial control simulation from the Geophysical Fluid Dynamics Laboratory (GFDL) Coupled Model version 2.1 (CM2.1).…”

Section: Other Drivers Of September Sea Ice Extent Variabilitymentioning

confidence: 99%

“…A number of processes have been suggested to explain the ice loss, but both observations and simulations from global climate models point to an increasing influence of warming from greenhouse gas forcing as a dominant driver of the observed sea ice loss (Stroeve and Notz, 2015;Kay et al, 2011). Natural variability has also played a role, including increased poleward transport of heat in both the ocean and atmosphere (Graversen et al, 2011;Zhang, 2015), an increase in downwelling long-wave radiation due to cloud cover (Francis et al, 2005), and changes in atmospheric circulation that enhance ice export out of the Arctic (Nghiem et al, 2007;Smedsrud et al, 2011). However, despite the large number of existing studies, the role and influence of natural variability remain unclear, especially on longer timescales than the current satellite data record.…”

Section: Introductionmentioning

confidence: 99%

Fram Strait sea ice export variability and September Arctic sea ice extent over the last 80 years

et al. 2017

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Abstract.A new long-term data record of Fram Strait sea ice area export from 1935 to 2014 is developed using a combination of satellite radar images and station observations of surface pressure across Fram Strait. This data record shows that the long-term annual mean export is about 880 000 km 2 , representing 10 % of the sea-ice-covered area inside the basin. The time series has large interannual and multi-decadal variability but no long-term trend. However, during the last decades, the amount of ice exported has increased, with several years having annual ice exports that exceeded 1 million km 2 . This increase is a result of faster southward ice drift speeds due to stronger southward geostrophic winds, largely explained by increasing surface pressure over Greenland. Evaluating the trend onwards from 1979 reveals an increase in annual ice export of about +6 % per decade, with spring and summer showing larger changes in ice export (+11 % per decade) compared to autumn and winter (+2.6 % per decade). Increased ice export during winter will generally result in new ice growth and contributes to thinning inside the Arctic Basin. Increased ice export during summer or spring will, in contrast, contribute directly to open water further north and a reduced summer sea ice extent through the ice-albedo feedback. Relatively low spring and summer export from 1950 to 1970 is thus consistent with a higher mid-September sea ice extent for these years. Our results are not sensitive to long-term change in Fram Strait sea ice concentration. We find a general moderate influence between export anomalies and the following September sea ice extent, explaining 18 % of the variance between 1935 and 2014, but with higher values since 2004.

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“…Since it is the warmest inflow branch, its transport of heat towards the Arctic will be even more dominant. A number of studies have emphasized the importance of this heat transport for Arctic sea ice (Årthun et al, 2012;Onarheim et al, 2014;Rippeth et al, 2015;Zhang, 2015;Polyakov et al, 2017) and it affects the regional climate and living conditions for fish stocks of significant economic potential (Mork et al, 2014;Utne et al, 2012).…”

Section: Discussionmentioning

confidence: 99%

Atlantic water flow through the Faroese Channels

Hansen¹,

Poulsen²,

Larsen³

et al. 2017

Ocean Sci.

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Abstract. Through the Faroese Channels -the collective name for a system of channels linking the Faroe-Shetland Channel, Wyville Thomson Basin, and Faroe Bank Channel -there is a deep flow of cold waters from Arctic regions that exit the system as overflow through the Faroe Bank Channel and across the Wyville Thomson Ridge. The upper layers, in contrast, are dominated by warm, saline water masses from the southwest, termed Atlantic water. In spite of intensive research over more than a century, there are still open questions on the passage of these waters through the system with conflicting views in recent literature. Of special note is the suggestion that there is a flow of Atlantic water from the Faroe-Shetland Channel through the Faroe Bank Channel, which circles the Faroes over the slope region in a clockwise direction. Here, we combine the observational evidence from ship-borne hydrography, moored current measurements, surface drifter tracks, and satellite altimetry to address these questions and propose a general scheme for the Atlantic water flow through this channel system. We find no evidence for a continuous flow of Atlantic water from the Faroe-Shetland Channel to the Faroe Bank Channel over the Faroese slope. Rather, the southwestward-flowing water over the Faroese slope of the Faroe-Shetland Channel is totally recirculated within the combined area of the Faroe-Shetland Channel and Wyville Thomson Basin, except possibly for a small release in the form of eddies. This does not exclude a possible westward flow over the southern tip of the Faroe Shelf, but even including that, we estimate that the average volume transport of a "Circum-Faroe Current" does not exceed 0.5 Sv (1 Sv = 10 6 m 3 s −1 ). Also, there seems to be a persistent flow of Atlantic water from the western part of the Faroe Bank Channel into the Faroe-Shetland Channel that joins the Slope Current over the Scottish slope. These conclusions will affect potential impacts from offshore activities in the region and they imply that recently published observational estimates of the transport of warm water towards the Arctic obtained by different methods are incompatible.

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Mechanisms for low-frequency variability of summer Arctic sea ice extent

Cited by 190 publications

References 52 publications

Improved Arctic sea ice thickness projections using bias-corrected CMIP5 simulations

Improved Arctic sea ice thickness projections using bias-corrected CMIP5 simulations

Fram Strait sea ice export variability and September Arctic sea ice extent over the last 80 years

Atlantic water flow through the Faroese Channels

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