Jeka: 2015

This week the institute, where I was working at, held the "ILTS International Symposium on Low Temperature Science" between 30 November and 2 December 2015. The symposium covered a huge variety of spatial and temporal scales and topics, studied in ILTS and by its collaborators: from a nanoscale to ice sheets, and from rapid ice crystal growth to orbitally-modulated ice ages. Below are some highlights of interesting talks:

Group photograph

(Photo: Dr. Shin Sugiyama / ILTS, Hokkaido University ©; See more photographs here).

Dr. N. Ebuchi, the ILTS director, introduced the institute and ongoing research, which is focused on 4 key directions: 1) water and material cycles, 2) frontier studies of ice and snow, 3) environmental biology; + Pan-Okhotsk division, which is focusing on the most southern sea-ice covered region in the world. The institute belongs to Hokkaido University (~28,000 people), collaborates with at least 21 other institutes in 13 countries, and contributes to education, in particular through educational program on theoretical and field cryoscience, called "International Antarctic Institute", which is made in English and later, though "Fuji scholarship", allows young Japanese scientists to work in Antarctic expeditions.

Dr. I. Weikusat (AWI) made an interesting review on "Ice physics in the light of global warming", where she showed an importance of ice fabric microscales to understanding of ice sheet evolution. In particular, beautiful numerical simulations by her collaborators and her (M.G. Llorens et al., ELLE/FFT) illustrated evolution of an ice crystal C-axis orientation under shear and dynamic re-crystallization, as well as kink bands formation in highly anisotropic material. (Deformation produces the major effect on C-axis, while re-crystallization mainly changes the crystal shape, i.e., a topology). At a larger scale, we were also shown a beautiful folding of intermediate layers due to anisotropy within Peterman Glacier, Greenland, before entering into its drain channel [Bonn et al., in review]. She also noted that famous EGRIP ice core drilling project, which now starts as collaboration between many countries, is the first physically motivated core. It is located away from the slow velocity ice divide and will bring new insights into ice stream physics.

Dr. T. Hiyama (Nagoya Univ.) presented his work on Eastern Siberia, starting from impressive photographs by Dr. Fedorov showing a degradation of permafrost-ecosystem (recently, pond formation due to thermocarst is intensifying). An interesting observation is that precipitation (liquid and solid), especially in summer, is increasing in this part of the world (not only ground ice is melting and producing more humid conditions). Probably this is somehow related sea-ice losses. He reported that high pressure at the North and low pressure at the South may facilitate humidity transport. This produces a higher river discharge in Siberia (and Canada). Also meaning a higher risk of flooding, since 2000 (in particular due to ice-jam floods, which are common in the region). For example, Lena river may have +8 m of water rise! Also, his long-term observation at "flux tower" in Siberia showed very beautiful variations of active layer soil temperature in relation to snow cover: snow insulates the soil and lead to warmer conditions under the surface.

Dr. G. Katul (Duke Univ.) presented a numerical study of hydraulic machinery of plants, including simulations of daily water pressure oscillation in plants, which can go as high at 1.5 MPa! Plants intake of water and a possible saturation of CO2 uptake are crucial for intensification of global warming and are presenting an important research direction.

Dr. H. Enomoto (NIPR) provided us with an interesting bi-polar perspective on sea-ice decrease in Arctic and increase around the Antarctic. For example, it is known that sea-ice covered area in Southern Ocean has been increasing (>1979) and even reached it maximum in 2014! Annual ice area change occurs out of phase in Northern Hemisphere and Southern Hemisphere (see interactive plots here at NIPR web-page; most recent and past sea-ice covered areas can be also studied here at another NIPR web-page). Another key difference is that: there is a limitless growth of sea-ice in Antarctica and bounded by continents growth in Arctic. Dynamics of sea-ice is very complex: for example, in Arctic major cracks may appear in February, or cyclon can reduce sea-ice very significantly (2012); in Antarctica due to weather conditions, divergence of sea-ice may cease and reverse to compaction, meaning that icebreakers (like Shirase) can be blocked by sea-ice. Beautiful animations of sea-ice dynamics can be found here. Dr. Enomoto noted that snow cover still remains one of the most poorly understood elements in the sea-ice system (snow thickness, albedo and even its weight are crucial for sea-ice formation).

Dr. S. Aoki (ILTS, Hokkaido Univ.) presented an ambitious Japanese national project "ROBOTICA" (2016-2022), which is focused on difficult-to-access margin of Antarctica where ice shelf interacts with the ocean and sea-ice at Lutzow-holm Bay near Syowa Station, East Antarctica. Today it is known that warm water intrusion is important for mass loss in West Antarctica, and that Antarctic bottom water is freshening [Aoki, 2013]. At Lutzow-holm Bay an intriguing semi-decadal periodicity in breakup of land-fasten ice was reported, but mechanisms remain unclear [Ushio, 2006]. Through comprehensive observations from Shirase icebreaker as a base for a feet of autonomous sub-water drones and geodesic observations on the surface of ice, the project aims to improve our understanding of ice-ocean interaction and evolution of water properties under the floating and marginal ice.

Dr. A. Abe-Ouchi (University of Tokyo) shared modeling results about mechanisms governing termination of ice ages [for more details see, Abe-Ouchi, Nature, 2013]. Ice ages periodicity can be seen from many proxies; e.g., Milankovich cycles can be seen in sea-level variation [Masson-Delmott, 2013]. During the last ice age maximum, ocean level dropped 120-130 m below present. And almost everytime the following thing happened: gradual drop and then an abrupt rise at the end of 100k yr cycle. There were many studies on this issue to suggest that large ice sheet and strong insulation conditions are needed for producing such effect. Also, indeed it is important that large ice sheet reaches low latitudes. Dr. A. Abe-Ouchi addressed this issue with a state-of-the-art numerical model, to show importance of various factors, including, for instance, delay in astenospheric isostatic re-bounce (~1000 yr) which causes important changes of the bed for cycles of ice ages. The study shows that insulation rise is leading ice age terminations, not CO2 gaz. CO2 was found as an important amplifier of the system (during strong insulation), but of minor importance for timing of ice cycles.

Dr. F. Saitoh (JAMSTEC), developer of IcIES ice-sheet model, illustrated how minor numerical variations (e.f., related to loss of trailing digit) can lead to major simulation differences [Saitoh, 2012]. He showed that prediction of some oscillations in ice sheet models is really difficult and that it is important to develop comparison procedures. He suggests that order of operations has to be preserved at all stages (... including work of a compiler and a processor, which is not easy humbly speaking...).

Dr. G. Sazaki (ILTS, Hokkaido Univ.) presented his work on ice crystal growth and, never-directly-seen before quasi-liquid layer on ice surface. Until recently, no one could see ice crystal surface at molecular level or show formation of surface melting features (due to many technical problems). Dr. Sazaki and his group developed advanced optical microscopy to work with an ice surface. Impressive video of layer-by-layer crystal growth can be seen at his web-page (note that each layer is equivalent to molecule thickness!!), and quasi-liquid droplets traveling on expanding crystal here. Detailed work showed that dislocations and defects play an important role on location of droplet formation, as well as impurities can melt ice dramatically. He believes that the possibility of in situ observations at molecular level will solve many mysteries of ice crystals during the next 10 years.

Dr. S. Fujita (NIPR) presented interesting analysis on firn densification at Antarctic plateau near Dome Fuji. He argues that textural effects and impurities control creep of firn. In particular, it is known that material properties of ice strongly depend on impurities, and was previously observed that ice age ice sometimes is 2.5 times softer, probably due to a high concentration of Cl^{- }. He analyzed dielectric permittivity of firn, which is a function of firn's anisotropy. According to core analysis anisotropy decreases with depth (down to 200 m). Another noted well known observation was that snow and ice is usually acidic in Antarctica (as it is usually in Japan and Northern Hemisphere).

Dr. T. Nakatsuka (RIHN, Kyoto) shared his recent research on Climate variations in East Asia and Japan for the last 200 yr basing on tree-rings. The latter sure as a proxy for temperature or precipitation (depending on local climate). For example, warm summer produces wide tree ring, while wet season produces the same effect in arid regions. PAGES-2k network published a review of different types of common proxies in Nature Geoscience [2013]. For Japan tree samples go as far as 5000 years, thanks not only to old trees (e.g. 1000 years), but also to remains of old wood in temples or excavated and dated archeological samples. One of large scale observations confers a decreasing intensity of summer mansion in East Asia during the last 200 years. Another intriguing possibility is periodicity in governmental regime in response to climate (related through rice yields, increases in population and linked to it population response). Russian scholar A. Chizhevskiy, who worked on such topic 100 years ago would be certainly happy to listen to this talk.

Dr. W. Park (GEOMAR, Kiel) discussed how understanding internal fluctuation in climate system gives us a better predictability of a climate. For example, re-emergence of some water masses back to surface is crucial for transfer of energy back to atmosphere. An interesting example was made about a polynia appearance in sea-ice 1975 near Antarctica due to warmer Southern Ocean. Multiple feedbacks exists: say, sea-ice increase -> air temperatures decreases -> and ocean can not interact freely with the atmosphere. It is known that most temperature rise has been observed in the Northern hemisphere. And it seems, that today the heat is being accumulated in Southern Ocean and can be released at some point. Another aspects of work in progress cover simulation of eddies at high resolution locally only at the most interesting places, to reduce expensive computations (AGRIF nests in GeoMar); or an attempt to introduce fresh water from melting Antarctic to see how water circulation responds.

Many other important talks were made, but now I have no more time to cover all them. Especially, an important contribution was described by

Dr. T. Aoki (MRI) who presented an impressive snowpit observations for 48 winters near ILTS. Unfortunately, snow physics and snowpack studies are almost gone today from the ILTS, which was a very strong center for such important studies (especially today, in the face of the climate change). Dr. Aoki presented an impressive modeling work focused on albedo and impurities effects on snow radiate properties. It would not be an exaggeration to say that their model is the most advanced in the field. Also,
Dr. J. Nishioka (NIPR) presented a large-scale collaboration between Japan and Russia focused on Pan-Okhotsk region, namely its biochemical system, which is an important source of iron for primary production in North Pacific ocean. In 2004 "JGR" had a special issue on the outcomes, and in 2015 "Progress in Oceanography" also released a special issue about their work in region.