Comparing methods of measuring sea-ice density in the East Antarctic

Remotely sensed derivation of sea-ice thickness requires sea·ice density. Sea-ice density was estimated with three techniques during the second Sea Ice Physics and Ecosystem eXperiment (SIPEX-II, September-November 2012, East Antarctica). The sea ice was first-year highly deformed, mean thickness 1.2 m with layers, consistent with rafting, and 6-7/10 columnar ice and 3/10 granular ice. Ice density was found to be lower than values (900-920 kg m⁻³ used previously to derive ice thickness, with columnar ice mean density of 870 kg m⁻³. At two different ice stations the mean density of the ice was 870 and 800 kg m⁻³, the lower density reflecting a high percentage of porous granular ice at the second station. Error estimates for mass/volume and liquid/solid water methods are presented. With 0.1 m long, 0.1 m core samples, the error on individual density estimates is 28 kg m⁻³. Errors are larger for smaller machined blocks. Errors increase to 46 kg m⁻³ if the liquid/solid volume method is used. The mass/volume method has a low bias due to brine drainage of at least 5%. Bulk densities estimated from ice and snow measurements along 100 m transects were high, and likely unrealistic as the assumption of isostatic balance is not suitable over these length scales in deformed ice

SIPEX-2: A study of sea-ice physical, biochemical and ecosystem processes off East Antarctica during spring 2012

This editorial introduces a suite of articles resulting from the second Sea Ice Physics and Ecosystems eXperiment(SIPEX-2) voyage by presenting some background information on the study areaandAntarcticsea-ice conditions,and summarising the key findings from the project.Using the Australian iceb reaker RV Aurora Australis, SIPEX-2 was conducted in the area between 115–125°E and 62–66°S off East Antarctica during September to November 2012. This region had been sampled during two previous experiments,i.e. ARISE in 2003 (Massom etal.,2006a) and SIPEX in 2007(Worbyetal.,2011a). The 2012 voyage combined traditional and newly developed sampling methods with satellite and other data to measure sea-ice physical properties and pro- cesses on large scales,which provided context for bio geochemical and ecological case studies. Thes pecific goals of the SIPEX-2 project were to:(i)measure the spatial variability in sea-ice and snow-cover properties over small-to regional-length scales;(ii) improve understanding of sea-ice kinematic processes;and(iii) advance knowledge of the links between sea-ice physical characteristics,sea-ice biogeochemical cycling and ice-associated food-web dynamics.Our field-based activities were designed to inform modelling approaches and to improve our capability to assess impacts of predicted changes in Antarctic sea ice on Southern Ocean biogeochemical cycles and ecosystem function

Helicopter-borne observation with portable microwave radiometer in the Southern Ocean and the Sea of Okhotsk

Spatial distribution of thin sea ice thickness and its variability is a key to accurate estimation of surface albedo, oceanatmosphere heat-fluxes, and rates of ice production and salt-flux. For the validation and improvement of the thin ice thickness algorithm using the satellite passive microwave data, we have done in-situ observations in thin ice region in the Southern Ocean and the Sea of Okhotsk, using a helicopter-borne portable passive microwave radiometer same sensor as the satellite launched Advanced Microwave Scanning Radiometer-EOS (AMSR-E) and Advanced Microwave Scanning Radiometer-2 (AMSR-2). High-resolution helicopter-borne results show good agreement with low-resolution AMSR-E/AMSR-2 results, within the range of the standard deviation. In the Sea of Okhotsk experiment, the results derived from the helicopter-borne sensor are fitting to the past thin ice thickness algorithm. In the Southern Ocean experiment, the polarization ratio of 36 GHz vertical and horizontal temperatures in the Dalton Iceberg Tongue Polynya in October is estimated to be 0.137 in average. This value does not conflict with past in-situ observations, theoretical models, and thin ice thickness algorithms. We further found the microwave characteristics of fast versus pack ice, leading to the improvement for the fast ice detection algorithm.第4回極域科学シンポジウム個別セッション：[OM] 気水圏11月15日（金） 統計数理研究所 ３階セミナー室１（D305

The state of the Martian climate

60°N was +2.0°C, relative to the 1981–2010 average value (Fig. 5.1). This marks a new high for the record. The average annual surface air temperature (SAT) anomaly for 2016 for land stations north of starting in 1900, and is a significant increase over the previous highest value of +1.2°C, which was observed in 2007, 2011, and 2015. Average global annual temperatures also showed record values in 2015 and 2016. Currently, the Arctic is warming at more than twice the rate of lower latitudes

State of the climate in 2018

In 2018, the dominant greenhouse gases released into Earth’s atmosphere—carbon dioxide, methane, and nitrous oxide—continued their increase. The annual global average carbon dioxide concentration at Earth’s surface was 407.4 ± 0.1 ppm, the highest in the modern instrumental record and in ice core records dating back 800 000 years. Combined, greenhouse gases and several halogenated gases contribute just over 3 W m−2 to radiative forcing and represent a nearly 43% increase since 1990. Carbon dioxide is responsible for about 65% of this radiative forcing. With a weak La Niña in early 2018 transitioning to a weak El Niño by the year’s end, the global surface (land and ocean) temperature was the fourth highest on record, with only 2015 through 2017 being warmer. Several European countries reported record high annual temperatures. There were also more high, and fewer low, temperature extremes than in nearly all of the 68-year extremes record. Madagascar recorded a record daily temperature of 40.5°C in Morondava in March, while South Korea set its record high of 41.0°C in August in Hongcheon. Nawabshah, Pakistan, recorded its highest temperature of 50.2°C, which may be a new daily world record for April. Globally, the annual lower troposphere temperature was third to seventh highest, depending on the dataset analyzed. The lower stratospheric temperature was approximately fifth lowest. The 2018 Arctic land surface temperature was 1.2°C above the 1981–2010 average, tying for third highest in the 118-year record, following 2016 and 2017. June’s Arctic snow cover extent was almost half of what it was 35 years ago. Across Greenland, however, regional summer temperatures were generally below or near average. Additionally, a satellite survey of 47 glaciers in Greenland indicated a net increase in area for the first time since records began in 1999. Increasing permafrost temperatures were reported at most observation sites in the Arctic, with the overall increase of 0.1°–0.2°C between 2017 and 2018 being comparable to the highest rate of warming ever observed in the region. On 17 March, Arctic sea ice extent marked the second smallest annual maximum in the 38-year record, larger than only 2017. The minimum extent in 2018 was reached on 19 September and again on 23 September, tying 2008 and 2010 for the sixth lowest extent on record. The 23 September date tied 1997 as the latest sea ice minimum date on record. First-year ice now dominates the ice cover, comprising 77% of the March 2018 ice pack compared to 55% during the 1980s. Because thinner, younger ice is more vulnerable to melting out in summer, this shift in sea ice age has contributed to the decreasing trend in minimum ice extent. Regionally, Bering Sea ice extent was at record lows for almost the entire 2017/18 ice season. For the Antarctic continent as a whole, 2018 was warmer than average. On the highest points of the Antarctic Plateau, the automatic weather station Relay (74°S) broke or tied six monthly temperature records throughout the year, with August breaking its record by nearly 8°C. However, cool conditions in the western Bellingshausen Sea and Amundsen Sea sector contributed to a low melt season overall for 2017/18. High SSTs contributed to low summer sea ice extent in the Ross and Weddell Seas in 2018, underpinning the second lowest Antarctic summer minimum sea ice extent on record. Despite conducive conditions for its formation, the ozone hole at its maximum extent in September was near the 2000–18 mean, likely due to an ongoing slow decline in stratospheric chlorine monoxide concentration. Across the oceans, globally averaged SST decreased slightly since the record El Niño year of 2016 but was still far above the climatological mean. On average, SST is increasing at a rate of 0.10° ± 0.01°C decade−1 since 1950. The warming appeared largest in the tropical Indian Ocean and smallest in the North Pacific. The deeper ocean continues to warm year after year. For the seventh consecutive year, global annual mean sea level became the highest in the 26-year record, rising to 81 mm above the 1993 average. As anticipated in a warming climate, the hydrological cycle over the ocean is accelerating: dry regions are becoming drier and wet regions rainier. Closer to the equator, 95 named tropical storms were observed during 2018, well above the 1981–2010 average of 82. Eleven tropical cyclones reached Saffir–Simpson scale Category 5 intensity. North Atlantic Major Hurricane Michael’s landfall intensity of 140 kt was the fourth strongest for any continental U.S. hurricane landfall in the 168-year record. Michael caused more than 30 fatalities and $25 billion (U.S. dollars) in damages. In the western North Pacific, Super Typhoon Mangkhut led to 160 fatalities and$6 billion (U.S. dollars) in damages across the Philippines, Hong Kong, Macau, mainland China, Guam, and the Northern Mariana Islands. Tropical Storm Son-Tinh was responsible for 170 fatalities in Vietnam and Laos. Nearly all the islands of Micronesia experienced at least moderate impacts from various tropical cyclones. Across land, many areas around the globe received copious precipitation, notable at different time scales. Rodrigues and Réunion Island near southern Africa each reported their third wettest year on record. In Hawaii, 1262 mm precipitation at Waipā Gardens (Kauai) on 14–15 April set a new U.S. record for 24-h precipitation. In Brazil, the city of Belo Horizonte received nearly 75 mm of rain in just 20 minutes, nearly half its monthly average. Globally, fire activity during 2018 was the lowest since the start of the record in 1997, with a combined burned area of about 500 million hectares. This reinforced the long-term downward trend in fire emissions driven by changes in land use in frequently burning savannas. However, wildfires burned 3.5 million hectares across the United States, well above the 2000–10 average of 2.7 million hectares. Combined, U.S. wildfire damages for the 2017 and 2018 wildfire seasons exceeded $40 billion (U.S. dollars)

Snow thickness profiling on Antarctic sea ice with GPR—Rapid and accurate measurements with the potential to upscale needles to a haystack

Snow thickness on sea ice is a largely undersampled parameter yet of importance for the sea ice mass balance and for satellite-based sea ice thickness estimates and thus our general understanding of global ice volume change. Traditional direct thickness measurements with meter sticks can provide accurate but only spot information, referred to as “needles” due to their pinpoint focus and information, while airborne and satellite remote sensing snow products, referred to as “the haystack,” have large uncertainties due to their scale. We demonstrate the remarkable accuracy and applicability of ground-penetrating radar (GPR) snow thickness measurements by comparing them with in situ meter stick data from two field campaigns to Antarctica in late winter/early spring. The efficiency and millimeter-to-centimeter accuracy of GPR enables practitioners to acquire extensive, semiregional data with the potential to upscale needles to the haystack and to potentially calibrate satellite remote sensing products that we confirm to derive roughly 30% of the in situ thickness. We find the radar wave propagation velocity in snow to be rather constant (± 6%), encouraging regional snow thickness surveys. Snow thinner than 10 cm is under the detection limit with the off-the-shelf GPR setup utilized in our study.publishedVersio

Sea ice conditions in the Transpolar Drift in August/September 2001 - Observations during POLARSTERN cruise ARKTIS 17/2

This report summarises visual shipboard ice observations carried out during leg ARKTIS 17/2 (ARK 17/2) of RV POLARSTERN in August and September 2001, operating along the Gakkel Ridge and at the North Pole. Data on general ice conditions, navigational information as well as photographs taken from the ships bridge are presented. Although most data are subject to large uncertainties due to the different experience of observers, they provide a general and quite representative overview of recent summer conditions in the Transpolar Drift, as seen from a ship. The data and photographs might be of interest as background information for discussions of recent changes of Arctic sea ice, and for comparisons with observations performed in other years. For those who have not seen a sea ice landscape so far, this report might yield first impressions of what the Arctic sea ice cover looks like. For scientists working on remote sensing, modelling, or other aspects of sea ice, the report provides some ground-truth and boundary conditions for their work in the summer of 2001. Ice conditions were characterised by very easily penetrable ice in the first half of the cruise, west of 30_E. There were many large leads with ice concentrations ranging between only 60% and 90%. Only from late August onwards, and east of 30_E, narrower leads and ice concentrations above 90% were observed. At that time, also new ice started to form on the leads. In the late period, sometimes the ship became beset in convergent ice conditions. Initially, melt ponds were observed to cover 10% to 30% of the ice surface. The ponds were ice covered already when we entered the ice in early August. However, the pond ice cover was thick enough to step on (>0.05 m) only after about August 20. Melt ponds became snow covered for some period, before they were visible again. Only after mid-September air temperatures permanently dropped below 0_C, and no snow or surface melting was observed any more