Aika: 12.11.2019 klo 17:00 - 19:00
Paikka: Tieteiden talo, sali 401 (Kirkkokatu 6, Helsinki)
Geofysiikan seuran syyskauden 2019 kolmannessa kuukausikokouksessa esitelmöi apulaisprofessori Bin Cheng (Ilmatieteen laitos) aiheesta
Snow and sea ice thermodynamics in the Polar Oceans: observation and modelling
The investigations of thermodynamics of snow and sea ice in the Polar Oceans are mainly focused on their mass balance. A thermistor string based ice mass balance (IMB) buoy called Snow and Ice Mass Balance Array (SIMBA) has been developed in recent years. SIMBA is a kind of innovative low-cost device that has the potential to be deployed with a large number in the Arctic to form an observation network. SIMBA measures vertical temperature profiles through the air-snow-ice-water column using a thermistor string (5 m long, sensor spacing 2cm). The temperature measurement was made 4 times a day. Each sensor on the SIMBA thermistor chain has a heating element. A small voltage was applied to the resistors so that the heat energy liberated in the vicinity of each sensor is the same. The heating time interval typically lasted for 60s and 120s, respectively. The sensor heating was made once per day and the temperature changes are used to identify the interfaces and further to retrieve snow depth and ice thickness. SIMBA buoys have built-in GPS to record buoy drift positions and the Iridium satellite is used for data transmission. A total 15 SIMBA buoys have been deployed in the Arctic Ocean during the Chinese National Arctic Research Expedition (CHINARE) 2018 and the Nansen and Amundsen Basins Observational System (NABOS) 2018 field expeditions in late autumn and some of 20 - 40 have been and will be deployed during the ongoing MOSAiC field campaign. We applied a recently developed SIMBA algorithm (Liao, et al., 2018) to retrieve snow and ice thickness from SIMBA temperature data. The results are compared with SIMBA heating temperature discriminated various interfaces.
A one-dimensional high-resolution snow and ice model (HIGHTSI) has been used to investigate snow and mass balance in the Polar Oceans (Launiainen and Cheng 1998, Cheng et al, 2008, Merkouriadi, et al., 2017, Zhao et al., 2017, 2019). In this presentation, some of these studies and results will be summarized. For example, in Prydz Bay, East Antarctica, snow has a major insulate effect on landfast ice thickness near costal region, while far from the coastal area, snow contribute to snow-ice and superimposed ice formation. HIGHTSI was also used to identify the factors that control the melting of second year ice (SYI) and freezing of first year ice (FYI) simultaneously in a confined area on Prydz Bay land-fast ice area.
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