Great Scott! Climate Change Deniers Accept Models!

A recent study of old log books, coupled with the use of computer modelling of ice estimates show that the summer sea ice edge then was further from the land in the Weddell sea but that ice conditions were surprisingly comparable to the present day in other sectors

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 (1897–1917), 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.

Some reports of this scientific paper, if they mention at all that the topic is sea ice, fail to refer to the other sectors.  Nor do they mention that the ice conditions back in time have been estimated.

In this study, we use sea ice edge positions recorded in the ship logbooks during the Heroic Age to estimate the mean summer ice edge latitude, both regionally and for the whole Antarctic, during the period 1897–1917. We compare these with modern satellite data in order to determine whether Antarctic summer sea ice extent was different to the present day and identify and quantify the possible changes.

Figure 1. Map of expedition routes taken by ships used in this study.
We only have coordinates for entry and departure of the pack ice for the 1901–1903 Gauss Expedition (Indian Ocean).

The Gauss enclosed in the ice. Photo taken from a captive balloon
Public domain image courtesy Wikimedia Commons.


Climate change deniers used to hate computer models, but that's all changed.  Reports that the Antarctic ice is growing or is stable, whether or not sea ice is specified, fail to mention the use of  models.

we have chosen to use the Bootstrap algorithm daily sea ice concentration from the National Snow and Ice Data Centre (NSIDC) to estimate the present-day sea ice edge, rather than NASA Team algorithm (Meier et al., 2013a; Peng et al., 2013). From this, we calculated a daily mean sea ice concentration for the period 1989–2014, during which daily data were available

Meanwhile, back in the real world, Antarctic sea ice is dropping.

After a reaching its maximum extent unusually early and then following a period of relatively unchanging overall extent, Antarctic sea ice extent started to decline in earnest. Daily sea ice extent levels have been at second lowest in the satellite record since October 20 and below the two standard deviation range. Only the 1986 austral spring extent is lower. Ice extent is particularly low on both sides of the Antarctic Peninsula. The rapid early reduction in sea ice cover in this region may create favorable conditions for the break up of the eastern Peninsula ice shelves at the end of austral summer. Similar sea ice trends and weather conditions were present during the spring seasons preceding past ice shelf retreats (e.g., 2001 to 2002). Extensive open water, created by the downsloping fosters warmer air and surface melting, and allows longer-period ocean waves to reach the ice front of the ice shelves. Other areas of reduced sea ice cover are the Southern Ocean north of Dronning Maud Land, and the area west of the Ross Sea and north of Wilkes Land.

Antarctic sea ice extent for October 2016 was 17.6 million square kilometers (6.8 million square miles). The magenta line shows the 1981 to 2010 median extent for that month. The black cross indicates the geographic South Pole.

Image and data courtesy NSIDC.


Now, if anyone tells you that the old log books of the likes of Scott and Shackleton prove that climate change is a hoax perpetrated by whoever, please do remember to laugh in their face.  Better still, get them to read the free-to-download pdf file of the original which is distributed
under the Creative Commons Attribution 3.0 License.

Sources:

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

Tom Edinburgh^1,a and Jonathan J. Day¹
1   Department of Meteorology, University of Reading, Reading, UK
a   currently at: Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Cambridge, UK

Pub. The Cryosphere.

Arctic Sea Ice News.