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

Abstract

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.

Arctic and Antarctic Sea Ice Change: Contrasts, Commonalities, and Causes

“…The two insets show satellite monthly ice extent anomalies for 1979-2017. a previous decline, an idea that is supported by consistent multidecadal variations in sea ice, sea surface and air temperatures, and zonal winds (Fan et al 2014). The shift in summer ice extent since the 1950s suggested by the whaling records may be spurious, as direct historical observations from the early 1900s indicate a more modest decline in extent of 14% (Edinburgh & Day 2016), which is within the satellite summer ice extent variability. Regionally, there is ice core proxy evidence for long-term positive trends since the mid-twentieth century in the Ross Sea (Thomas & Abram 2016) and eastern Antarctic (Curran et al 2003) and for negative trends in the Bellingshausen Sea (Abram et al 2010).…”

Understanding weather and climate of the last 300 years from ships' logbooks

“…But there are other examples. The recent work by Edinburgh and Day (2016) comparing ships' logbooks from 1897 to 1917 with satellite records from 1989 to 2014 has made it possible to show that the summer sea ice limit was at that time more than 1 north of its current location in the Weddel Sea, but comparable to present day in other areas of Antarctica. An active field of debate deals with the uncertainties in the trend of North Atlantic tropical cyclone frequency, which complicates the evaluation of the anthropogenic impact.…”

Understanding the Seasonal Cycle of Antarctic Sea Ice Extent in the Context of Longer‐Term Variability

“…Methane sulphonic acid has been shown to give a reliable estimate of regional sea ice cover on interannual time scales (Abram et al, ). In addition, historical records from whale catch locations (de la Mare, ) and observations of the summer ice edge from ship logbooks from the “Heroic Age” of Antarctic exploration (Edinburgh & Day, ) have been used to estimate SIE from the late nineteenth century onward. Early satellite missions have also provided snapshot estimates of SIE since 1964 (Meier et al, ).…”