The Satellite Passive-Microwave Record of Sea Ice in the Ross Sea Since Late 1978

Satellites have provided us with a remarkable ability to monitor many aspects of the globe day-in and day-out and sea ice is one of numerous variables that by now have quite substantial satellite records. Passive-microwave data have been particularly valuable in sea ice monitoring, with a record that extends back to August 1987 on daily basis (for most of the period), to November 1970 on a less complete basis (again for most of the period), and to December 1972 on a less complete basis. For the period since November 1970, Ross Sea sea ice imagery is available at spatial resolution of approximately 25 km. This allows good depictions of the seasonal advance and retreat of the ice cover each year, along with its marked interannual variability. The Ross Sea ice extent typically reaches a minimum of approximately 0.7 x 10(exp 6) square kilometers in February, rising to a maximum of approximately 4.0 x 10(exp 6) square kilometers in September, with much variability among years for both those numbers. The Ross Sea images show clearly the day-by-day activity greatly from year to year. Animations of the data help to highlight the dynamic nature of the Ross Sea ice cover. The satellite data also allow calculation of trends in the ice cover over the period of the satellite record. Using linear least-squares fits, the Ross Sea ice extent increased at an average rate of 12,600 plus or minus 1,800 square kilometers per year between November 1978 and December 2007, with every month exhibiting increased ice extent and the rates of increase ranging from a low of 7,500 plus or minus 5,000 square kilometers per year for the February ice extents to a high of 20,300 plus or minus 6,100 kilometers per year for the October ice extents. On a yearly average basis, for 1979-2007 the Ross Sea ice extent increased at a rate of 4.8 plus or minus 1.6 % per decade. Placing the Ross Sea in the context of the Southern Ocean as a whole, over the November 1978-December 2007 period the Ross Sea had the highest rate of increase in sea ice coverage of any of five standard divisions of the Southern Ocean, although the Weddell Sea, Indian Ocean, and Western Pacific Ocean all also had sea ice increases, while only the Bellingshausen/Smundsen Seas experienced overall sea ice decreases. Overall, the Southern Ocean sea ice cover increased at an average rate of 10,800 plus or minus 2,500 square kilometers per year between November 1978 and December 2007, with every month showing positive values although with some of these values not being statistically significant. The sea ice increase since November 1978 was preceded by a sharp decrease in Southern Ocean ice coverage in the 1970's and is in marked contrast to the decrease in Arctic sea ice coverage that has occurred both in the period since November 1978 and since earlier in the 1970's. On a yearly average bases, for 1979-2007 the Southern Ocean sea ice extent increased at a rate of 1.0 plus or minus 0.4% per decade, whereas the Arctic ice extent decreased at the much greater rate of 4.0 plus or minus 0.4 percent per decade (closer to the % per decade rate of increase in the Ross Sea). Considerable research is ongoing to explain the differences

Variability of Arctic Sea Ice: The View from Space, An 18-year Record

A recently compiled 18-year record (1979 to 1996) of sea ice concentrations derived from four passive-microwave satellite instruments has allowed the quantification of a variety of measures of Arctic sea ice variability. Earlier maps generated using data through August 1987 have been updated to 18-year summaries of the annual range of sea ice distributions, the interannual variability of average monthly sea ice distributions, the frequency of sea ice coverage over the 18 years, the length of the sea ice season, and trends in the length of the sea ice season. Linear least squares trends over the 18-year record show the sea ice season to have lengthened over some sizeable regions, especially in the Bering Sea, Baffin Bay, Davis Strait, the Labrador Sea, and the Gulf of St. Lawrence, but to have shortened over a much larger area, including the Sea of Okhotsk, the Greenland Sea, the Barents Sea, and all the seas along the north coast of Russia. The area with trends showing sea ice seasons shortening by over 0.5 days/year is 7 500 000 km², over 2.5 times the area experiencing a lengthening of the sea ice season by over 0.5 days/year. Neither the shortening nor the lengthening, however, is uniform or monotonic over the 18-year record. Instead, the ice cover exhibits widespread interannual variability, not just in the length of the sea ice season but for each month-a fact well illustrated by the monthly average September ice coverage, which was at its lowest extent in 1995 but at its second highest one year later, in the final year of the record. The maps of ice frequency and ice variability can help identify how anomalous individual years are. In some cases, they can help forestall unnecessary concern over seemingly unusual conditions which, upon examination of the maps, are found to fall well within the observed variability. Grâce à un dossier compilant 18 années d'étude (de 1979 à 1996) sur les concentrations de glace marine mesurées par quatre instruments à hyperfréquences passives portés sur des satellites, on a pu quantifier diverses mesures de la variabilité de la glace marine dans l'Arctique. Les premières cartes créées à l'aide de données allant jusqu'en août 1987 ont été mises à jour sous forme de résumés (portant sur une période de18 ans) de la superficie annuelle des distributions de glace marine, de la variabilité interannuelle de la moyenne mensuelle des distributions de glace marine, de la fréquence de la couverture de glace marine au cours des 18 années, de la durée de la saison de glace marine et des tendances dans cette même durée. Une analyse des tendances, par la méthode linéaire des moindres carrés, enregistrées sur 18 ans montre que la saison de glace marine est devenue plus longue dans certaines régions assez vastes, surtout dans la mer de Béring, la baie de Baffin, le détroit de Davis, la mer du Labrador et le golfe du Saint-Laurent, mais qu'elle a raccourci dans une zone bien plus étendue, qui comprend la mer d'Okhotsk, la mer de Norvège, la mer de Barents et toutes les eaux longeant la côte nord de Russie. La région où se manifestent les tendances au raccourcissement de la saison de glace marine de 0,5 jour/an s'étend sur 7 500 000 km², soit plus de 2,5 fois l'étendue où se manifeste une extension de la saison de glace marine de 0,5 jour/an. Mais ni le raccourcissement ni l'extension ne sont uniformes ou monotones au cours des 18 années d'études. La couverture de glace affiche, au contraire, une variabilité interannuelle généralisée, non seulement dans la longueur de la saison de glace marine, mais pour chaque mois - fait qu'illustre bien la moyenne mensuelle de la couverture de glace pour le mois de septembre, moyenne qui était à son minimum en 1995, mais à son maximum de second rang un an plus tard, durant l'année finale de l'enregistrement. Les cartes de fréquence de la glace et de variabilité de la glace peuvent montrer les anomalies d'une année à l'autre. Dans certains cas, ces cartes peuvent aider à prévenir d'inutiles soucis quant aux conditions apparemment inhabituelles qui, si l'on étudie les cartes, se situent parfaitement dans la fourchette de variabilité observée

Coming Climate Crisis? Perhaps, but Beware the Solutions

Over the past several decades, there has been a growing awareness that climate changes in substantial ways, that human activities are having an impact on climate change, and that climate change can have major consequences for human societies. Unfortunately, along with this realization has come a strong polarization within the scientific community and outside of it regarding what if anything should be done to reduce negative human impacts and/or to attempt to control climate. This book places recent climate change in the context of the very long term history of change on planet Earth and warns that our understanding of climate change remains sufficiently incomplete that we should be extremely cautious about implementing proposed massive geoengineering schemes intended to alter future climate conditions. The book treats with respect the various viewpoints in the highly polarized discussions regarding climate change, following a basic assumption that the major scientists on each side of the issues have valuable points to bring to the table. The topic is too important to become endlessly mired in contentious polarization

A 40-Y Record Reveals Gradual Antarctic Sea Ice Increases Followed by Decreases at Rates Far Exceeding the Rates Seen in the Arctic

Following over 3 decades of gradual but uneven increases in sea ice coverage, the yearly average Antarctic sea ice extents reached a record high of 12.8 by 10 (sup 6) square kilometers in 2014, followed by a decline so precipitous that they reached their lowest value in the 40-year 1979-2018 satellite multichannel passive-microwave record, 10.7 by 10 (sup 6) square kilometers, in 2017. In contrast, it took the Arctic sea ice cover a full 3 decades to register a loss that great in yearly average ice extents. Still, when considering the 40-year record as a whole, the Antarctic sea ice continues to have a positive overall trend in yearly average ice extents, although at 11,300 plus or minus 5,300 square kilometers per year, this trend is only 50 percent of the trend for 1979-2014, before the precipitous decline. Four of the 5 sectors into which the Antarctic sea ice cover is divided all also have 40-year positive trends that are well reduced from their 2014-2017 values. The one anomalous sector in this regard,the Bellingshausen/Amundsen Seas, has a 40-year negative trend, with the yearly average ice extents decreasing overall in the first 3 decades, reaching a minimum in 2007, and exhibiting an overall upward trend since 2007 (i.e., reflecting a reversal in the opposite direction from the other 4 sectors and the Antarctic sea ice cover as a whole)

Review of Mariana Gosnell's 'ICE: The Nature, the History, and the Uses of an Astonishing Substance'

ICE: The Nature, the History, and the Uses of an Astonishing Substance is a recently published book by Mariana Gosnell about ice. It covers not just the ice that is readily seen, such as sea ice, lake ice, icebergs, glaciers, ice sheets, and ice cubes, but also ice in the ground, in the atmosphere, inside plants and animals, and in outer space, plus new ice forms being created in scientific laboratories. Gosnell treats the reader to a well-written, easy-going mixture of science, adventure, history, applications, science methods and controversies, and philosophy, all centered in one way or another on ice. The book is 563 pages long and is filled with fascinating anecdotes and details, such as beetles in the Canadian Rockies that can supercool to 60 C below freezing and a lake in Minnesota where each winter typically 65,000 fishing shanties are set up on the lake's ice, many with couches, beds, television sets, and bathrooms. Gosnell also includes many practical suggestions. Among them: When driving on lake ice, keep your windows open, in case your vehicle breaks through the ice and you need to make a rapid exit