Seminars

The Earth Observation group organizes seminars in collaboration with CIRFA on various topics connected to the satellite remote sensing of the Arctic. The seminars are normally taking place in the EO group office at Forskingsparken on Thursdays at 14:00. Participation in person is encouraged, but an online attendance is possible. The seminars are announced here and on a mailing list. To join the mailing list contact polona.itkin@uit.no or johannes.p.lohse@uit.no

CIRFA seminar (7 December): Torbjørn Eltoft – Sea Ice Physics by Radar Polarimetry

In our last CIRFA seminar and the last UiT Earth Observation group seminar this year Torbjorn Eltoft will talk about the use of radar polarimetry for sea ice research. This will be a special seminar to celebrate 8 years of CIRFA and more than 40 years of Torbjørn's research.

The seminar will take place at the EO group office on Thursday 7 December at 14:00. Join us in person or online (MS Teams)!

CIRFA seminar (16 November): Anne Braakmann-Folgmann – Remote Sensing and AI for Antarctic Icebergs

This Thursday we will hear about the icebergs in the Southern Ocean. Anne Braakmann-Folgmann has recently joined our group as post-doc in the INTERAAC project as sea ice altimetry specialist. In the seminar she will tell us about her PhD project work.

Icebergs release cold, fresh water and terrigenous nutrients as they drift and melt, influencing the local ocean properties and encouraging sea ice formation and biological production. To locate and quantify the freshwater flux from Antarctic icebergs, changes in their area and thickness have to be monitored. Iceberg thickness and changes in thickness attributed to basal melting are derived from satellite radar and laser altimetry observations (CryoSat-2 and ICESat-2). We manually chart iceberg area in radar and optical satellite images (Sentinel-1, Sentinel-3 and MODIS) and calculate iceberg fragmentation over several years for two giant icebergs (A68A and B30). Combining area and thickness measurements yields estimates of volume and mass loss. We find that the A68A iceberg lost 802 ± 34 Gt of ice along its trajectory. Near South Georgia, 152 ± 61 Gt were released through basal melting alone within 3 months. Finally, we develop a deep neural network (based on U-net) to map the extent of giant icebergs in Sentinel-1 imagery automatically. While each manual delineation takes several minutes, U-net reduces the time to 0.01 second. Evaluating the performance compared to two standard segmentation techniques (Otsu and k-means), we find that U-net achieves a higher F1 score (0.84 versus 0.62) and is more robust to sea ice, other icebergs and nearby coast.

The seminar will take place at the EO group office on Thursday 16 November at 14:00. Join us in person or online (MS Teams)!

CIRFA seminar (2 November): Laust Færch and Henrik Fisser – Satellite Remote Sensing of Arctic Icebergs

Our PhD students Laust Færch and Henrik Fisser will share the stage and talk about their ongoing work with the detection of icebergs by SAR and optical satellite images.

Icebergs are large pieces of freshwater ice that break off from marine-terminating glaciers and ice shelves. Iceberg calving contributes to the glacier mass balance and their melt releases freshwater into the ocean. Furthermore, icebergs can be a hazard to shipping and offshore infrastructures. Therefore, it is crucial to quantify and understand iceberg occurrences in space and time. Synthetic aperture radar data at different frequencies and optical data offer valuable capabilities to detect and delineate icebergs. In this episode of the CIRFA seminar, we will present results on Arctic iceberg detection, and open a discussion on the inherent relationship between icebergs and sea ice.

The seminar will take place at the EO group office on Thursday 2 November at 14:00. Join us in person or online (MS Teams)!

CIRFA seminar (19 October): Øyvind Lundesgård – Sea ice draft from ULS moornings

Øyvind Lundesgård, Norwegian Polar Institute will talk about Sea ice draft in the northern Barents Sea: Multi-year local observations in a large-scale context

Sea ice thickness remains a crucial but elusive variable, influenced by many different processes and challenging to observe both from space and in situ. In this seminar, we explore time series of sea ice draft in the northwestern Barents Sea measured by moored instruments, and zoom out to examine various remote sensing products to contextualize these local observations. The picture that emerges is one of a highly dynamic sea ice region, heavily influenced by winds, thermal ocean forcing, interactions with the coasts, and the seasonal arrival of ice from the Transpolar Drift.

The seminar will take place at the EO group office on Thursday 19 October at 14:00. Join us in person or online (MS Teams)!

CIRFA seminar (5 October): Qiang Wang – Ice mapping and deep learning

Qiang Wang, UiT The Arctic University of Norway will talk about Pixel-wise sea ice mapping with deep learning.

Sentinel-1 HH,HV backscatter coefficient in (a) and (b) as well as our inference in (c) Credit: Qiang Wang

Monitoring sea ice in polar regions is critical for understanding global climate change and supporting marine navigation. Currently, ice charting is the main resource for understanding the sea ice status. However, the spatial resolution of ice-charting is in the order of km, which is not enough for some applications, for instance, search -and-rescue, offshore operation close to the coast , etc. Here, we present a deep learning-based method to generate sea ice map in the polar region by using Sentinel-1 dataset. Meanwhile, an incidence angle based data augmentation scheme is being utilized to enrich the training dataset in our methodology.

The seminar will take place at the EO group office on Thursday 5 October at 14:00. Join us in person or online (MS Teams)!

CIRFA seminar (28 September): Wolfgang Dierking – Multi-frequency multi-polarization SAR

Wolfgang Dierking, UiT The Arctic University of Norway will talk about Multi-frequency multi-polarization SAR – how to relate radar signature variations to specific tasks of information retrieval?

An example of a multi-frequency composite image from F-SAR campaign in April 2019 over the first-year ice in Davis Strait, R-X, G-C, B-L, all VV-polarization. Credits: Wolfgang Dierking

With multi-frequency polarimetric SAR images we get the possibility to calculate a large variety of radar signature parameters to be used for interpretation of sea ice conditions in ice charting and for the retrieval of sea ice properties related to questions of ocean – ice – atmosphere interactions. However, in practical terms several fixed factors determine the actual possibilities for information retrieval from satellite SAR data, such as spatial resolution of the images, temporal gaps and spatial overlaps between acquisitions at different frequencies, and availability of complementary data to support or validate the image analysis. For basic investigations and developing optimal strategies for information retrieval, simultaneous polarimetric measurements at different frequencies from airplanes are most useful. In this presentation, preliminary results of airborne polarimetric data acquisitions at L-, C-, and X-band, carried out in April 2019 by DLR’s F-SAR over first-year sea ice in Davis Strait, supplemented by hand-held aerial photos, will be introduced. The focus is on the use of radar intensities at VV, HH, and X-polarization and polarimetric phase difference and correlation HH-VV. Questions are how the radar signature variations relate to ice type separation and retrieval of thin ice properties.

The seminar will take place at the EO group office on Thursday 28 September at 14:00. Join us in person or online (MS Teams)!