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Today’s Arctic Compares with 150 years ago

Imagery date refers to Google Earth capture of land forms. Ice extent is for August 31, 2016 from MASIE. Serenity is docked at Devon Island.

By Ron Clutz | Science Matters | November 28, 2016

Researchers found that ice conditions in the 19th century were remarkably similar to today’s, observations falling within normal variability. The study is Accounts from 19th-century Canadian Arctic Explorers’ Logs Reflect Present Climate Conditions (here) by James E. Overland, Pacific Marine Environmental Laboratory/NOAA, Seattle,Wash., and Kevin Wood, Arctic Research Office/NOAA, Silver Spring, Md.   H/t GWPF

Overview

This article demonstrates the use of historical instrument and descriptive records to assess the hypothesis that environmental conditions observed by 19th-century explorers in the Canadian archipelago were consistent with a Little Ice Age as evident in proxy records. We find little evidence for extreme cold conditions.

It is clear that the first-hand observations of 19th-century explorers are not consistent with the hypothesized severe conditions of a multi-decadal Little Ice Age. Explorers encountered both warm and cool seasons, and generally typical ice conditions, in comparison to 20th-century norms.

Analysis

There were more than seventy expeditions or scientific enterprises of various types dispatched to the Canadian Arctic in the period between 1818 and 1910. From this number, we analyzed 44 original scientific reports and related narratives; many from expeditions spanning several years. The majority of the data come from large naval expeditions that wintered over in the Arctic and had the capacity to support an intensive scientific effort. A table listing the expeditions and data types is located at http://www.pmel.noaa.gov/arctic/history. The data cover about one-third of the possible number of years depending on data type, and every decade is represented.

Our analysis focuses on four indicators of climatic change: summer sea ice extent, annual sea ice thickness, monthly mean temperature, and the onset of melt and freeze as estimated from daily mean temperature. Historical observations in these four categories were compared with modern reference data; the reference period varied, depending on data availability. Both sea ice extent and the onset of melt and freeze were compared to the 30- year reference period 1971–2000; monthly means are compared to the 50-year period 1951–2000. Modern sea ice thickness records are less continuous, and some terminate in the 1980s; the reference period is therefore based on 19 to 26 years of homogeneous record.

Fig.1.

(a) Proxy record of standardized summer air temperature variation derived from ice cores taken on Devon Island. This proxy record suggests that a significantly colder climate prevailed in the 19th century. Shading indicates temperatures one standard deviation warmer or colder than average for the reference period 1901–1960 [Overpeck,1998].

(b) Historical monthly mean temperature observations compared to the 20th-century reference period 1951–2000. Sixty-three percent of 343 monthly mean temperatures recorded on 19th-century expeditions between 1819 and 1854 fall within one standard deviation of the reference mean at nearby stations (reference data from Meteorological Service of Canada,2002; and National Climatic Data Center,2002).

(c) Onset of melt observed by expeditions between 1820 and 1906 expressed as departures from the mean for the reference period 1971–2000. The period of melt transition observed by 19th century explorers is not inconsistent with modern values.

(d) Onset of freeze observed between 1819 and 1905 compared to the reference period 1971–2000. The onset of freeze transition is frequently consistent with modern values,but in some cases occurred earlier than usual. The incidence of an early onset of freeze represents the largest departure from present conditions evident in the historical records examined in this study. Melt and freeze transition dates for the reference period 1971–2000 were calculated from temperature data extracted from the Global Daily Climatology Network data base (National Climate Data Center, 2002).

Fig.2. The ship tracks and winter-over locations of Arctic discovery expeditions from 1818 to 1859 are surprisingly consistent with present sea ice climatology (contours represented by shades of blue). The climatology shown reflects percent frequency of sea ice presence on 10 September which is the usual date of annual ice minimum for the reference period 1971–2000 (Canadian Ice Service,2002). On a number of occasions, expeditions came within 150 km of completing the Northwest Passage, but even in years with unfavorable ice conditions, most ships were still able to reach comparatively advanced positions within the Canadian archipelago. By 1859, all possible routes comprising the Northwest Passage had been discovered.

Summary

As stated here before, Arctic ice is part of a self-oscillating system with extents expanding and retreating according to processes internal to the ocean-ice-atmosphere components. We don’t know exactly why 19th century ice extent was less than previously or less than the 1970s, but we can be sure it wasn’t due to fossil fuel emissions.

Explorers encountered both favorable and unfavorable ice conditions. This drawing from the vicinity of Beechey Island illustrates the situation of the H.M.S.Resolute and the steam-tender Pioneer on 5 September 1850 [from Facsimile of the Illustrated Arctic News, courtesy of Elmer E. Rasmuson Library, Univ. of Alaska Fairbanks].

November 29, 2016 - Posted by aletho | Science and Pseudo-Science, Timeless or most popular | Canada