Changes in Antarctic sea-ice extent from direct historical observations and whaling records

Mare, William K. de la

doi:10.1007/s10584-008-9473-2

Cited by 51 publications

(36 citation statements)

References 31 publications

(47 reference statements)

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“…Estimates of SIE based on ship log books [Edinburgh and Day, 2016] and whaling records [de la Mare, 2009] indicate a decrease in summer SIE Weddell Sea ice cover since the early twentieth century, consistent with the SOFI MJJ reconstruction. Coastal surface temperature records indicate a decrease in Bellingshausen SIE in all seasons since the mid-twentieth century [King and Harangozo, 1998] in agreement with the ABS reconstruction.…”

Section: 1002/2016jc012111supporting

confidence: 54%

Century‐scale perspectives on observed and simulated Southern Ocean sea ice trends from proxy reconstructions

et al. 2016

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Since 1979 when continuous satellite observations began, Southern Ocean sea ice cover has increased, whilst global coupled climate models simulate a decrease over the same period. It is uncertain whether the observed trends are anthropogenically forced or due to internal variability, or whether the apparent discrepancy between models and observations can be explained by internal variability. The shortness of the satellite record is one source of this uncertainty, and a possible solution is to use proxy reconstructions, which extend the analysis period but at the expense of higher observational uncertainty. In this work, we evaluate the utility for change detection of 20th century Southern Ocean sea ice proxies. We find that there are reliable proxies for the East Antarctic, Amundsen, Bellingshausen and Weddell sectors in late winter, and for the Weddell Sea in late autumn. Models and reconstructions agree that sea ice extent in the East Antarctic, Amundsen and Bellingshausen Seas has decreased since the early 1970s, consistent with an anthropogenic response. However, the decrease is small compared to internal variability, and the change is not robustly detectable. We also find that optimal fingerprinting filters out much of the uncertainty in proxy reconstructions. The Ross Sea is a confounding factor, with a significant increase in sea ice since 1979 that is not captured by climate models; however, existing proxy reconstructions of this region are not yet sufficiently reliable for formal change detection.

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Section: 1002/2016jc012111supporting

confidence: 54%

Century‐scale perspectives on observed and simulated Southern Ocean sea ice trends from proxy reconstructions

et al. 2016

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“…Previous studies, using these catch positions as a proxy record for the ice edge, suggested a 2.8 • southward shift in the mean latitude of the summer sea ice edge, equating to a 25 % decline sea ice extent between 1931-1961and 1971-1987(Cotté and Guinet, 2007de la Mare, 1997). However, there is some disagreement over the magnitude and spatial nature of results inferred from these records (Ackley et al, 2003;de la Mare, 2009), in part due to the accuracy of the satellite-derived ice during the summer melt season (Worby and Comiso, 2004) but also due to the evolution of whaling practices in the Southern Ocean (Vaughan, 2000). However, the ice decline documented by de la Mare (1997Mare ( , 2009) is consistent with a significant warming of the Southern Ocean between 1950 and 1978 documented recently by Fan et al (2014).…”

Section: Introductionmentioning

confidence: 93%

“…However, there is some disagreement over the magnitude and spatial nature of results inferred from these records (Ackley et al, 2003;de la Mare, 2009), in part due to the accuracy of the satellite-derived ice during the summer melt season (Worby and Comiso, 2004) but also due to the evolution of whaling practices in the Southern Ocean (Vaughan, 2000). However, the ice decline documented by de la Mare (1997Mare ( , 2009) is consistent with a significant warming of the Southern Ocean between 1950 and 1978 documented recently by Fan et al (2014). Whale catch records from earlier periods, in particular the Heroic Age, have not yet been used in sea ice analysis.…”

Section: Introductionmentioning

confidence: 99%

Estimating the extent of Antarctic summer sea ice during the Heroic Age of Antarctic Exploration

Edinburgh

Day

2016

The Cryosphere

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Abstract. In stark contrast to the sharp decline in Arctic sea ice, there has been a steady increase in ice extent around Antarctica during the last three decades, especially in the Weddell and Ross seas. In general, climate models do not to capture this trend and a lack of information about sea ice coverage in the pre-satellite period limits our ability to quantify the sensitivity of sea ice to climate change and robustly validate climate models. However, evidence of the presence and nature of sea ice was often recorded during early Antarctic exploration, though these sources have not previously been explored or exploited until now. We have analysed observations of the summer sea ice edge from the ship logbooks of explorers such as Robert Falcon Scott, Ernest Shackleton and their contemporaries during the Heroic Age of Antarctic Exploration (1897Exploration ( -1917, and in this study we compare these to satellite observations from the period 1989-2014, offering insight into the ice conditions of this period, from direct observations, for the first time. This comparison shows that the summer sea ice edge was between 1.0 and 1.7 • further north in the Weddell Sea during this period but that ice conditions were surprisingly comparable to the present day in other sectors.

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“…Models indicate that the continued warming of the Earth's climate will result in a 33% decline in Antarctic SIE by 2100 (Bracegirdle et al, 2008). Historical records (whaling records, ice charts, and direct observations) and concentrations of methane sulfonic acid in ice cores suggest SIE has declined at least 20% since the 1950s (Curran et al, 2003;de la Mare, 2009). …”

Section: Seasonal Sea Ice Zonementioning

confidence: 99%

Southern Ocean Phytoplankton in a Changing Climate

2017

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Phytoplankton are the base of the Antarctic food web, sustain the wealth and diversity of life for which Antarctica is renowned, and play a critical role in biogeochemical cycles that mediate global climate. Over the vast expanse of the Southern Ocean (SO), the climate is variously predicted to experience increased warming, strengthening wind, acidification, shallowing mixed layer depths, increased light (and UV), changes in upwelling and nutrient replenishment, declining sea ice, reduced salinity, and the southward migration of ocean fronts. These changes are expected to alter the structure and function of phytoplankton communities in the SO. The diverse environments contained within the vast expanse of the SO will be impacted differently by climate change; causing the identity and the magnitude of environmental factors driving biotic change to vary within and among bioregions. Predicting the net effect of multiple climate-induced stressors over a range of environments is complex. Yet understanding the response of SO phytoplankton to climate change is vital if we are to predict the future state/s of the ecosystem, estimate the impacts on fisheries and endangered species, and accurately predict the effects of physical and biotic change in the SO on global climate. This review looks at the major environmental factors that define the structure and function of phytoplankton communities in the SO, examines the forecast changes in the SO environment, predicts the likely effect of these changes on phytoplankton, and considers the ramifications for trophodynamics and feedbacks to global climate change. Predictions strongly suggest that all regions of the SO will experience changes in phytoplankton productivity and community composition with climate change. The nature, and even the sign, of these changes varies within and among regions and will depend upon the magnitude and sequence in which these environmental changes are imposed. It is likely that predicted changes to phytoplankton communities will affect SO biogeochemistry, carbon export, and nutrition for higher trophic levels.

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Changes in Antarctic sea-ice extent from direct historical observations and whaling records

Cited by 51 publications

References 31 publications

Century‐scale perspectives on observed and simulated Southern Ocean sea ice trends from proxy reconstructions

Century‐scale perspectives on observed and simulated Southern Ocean sea ice trends from proxy reconstructions

Estimating the extent of Antarctic summer sea ice during the Heroic Age of Antarctic Exploration

Southern Ocean Phytoplankton in a Changing Climate

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