Welcome to the first CIRFA Seminar after the summer break on August 27, kl. 14:00-15:00! Naomi Ochwat will talk about the Break-Up of Hunt Fjord Ice Shelf, Northern Greenland, and Jack Landy will share insights on Exploiting a growing fleet of satellite altimeters to gain new perspectives on the Arctic’s ocean and ice cover. Welcome to the seminar! Join Microsoft Teams Meeting here.
Naomi Ochwat: Break-Up of Hunt Fjord Ice Shelf, Northern Greenland
The polar regions are particularly responsive to changes in the climate; the cryosphere in particular can act as the “canary in the coal mine” for changes that are likely to occur at lower latitudes. One feature of the high Arctic that is experiencing irreversible changes is the Arctic Ice Shelves. The Hunt Fjord Ice Shelf is potentially the last remaining Arctic-style ice shelf in Northern Greenland, composed of a mixture of multi-decadal folded fast ice and floating ice tongues. Its characteristics are similar to that of the Ellesmere Ice Shelves that have recently undergone collapse. Hunt Fjord Ice Shelf experienced significant calving and break-up on July 27th 2019 and is continuing to lose area in 2020. This project utilizes multi-sensor remote sensing methods to explore the characteristics of Hunt Fjord Ice Shelf, its evolution over the past several decades, and the processes leading to its demise. ICESat1 & 2 data, in conjunction with a 1978 photogrammetric derived DEM and the ArcticDEM, are used to assess the extent of ice thickness changes (if any) that have occurred in the last decade. Landsat 8 off-nadir imagery is used to determine outlet glacier ice velocities and to assess the structural characteristics of the ice shelf. Compared with a previous study on Hunt Fjord, flow velocity of the front western outlet glaciers has significantly increased since 1978. Sea ice concentration data and comparison to previous studies on the Ellesmere Ice Shelves show that the break-up events at Hunt Fjord coincide with the retreat of sea ice and the increased exposure to open water for prolonged periods of time (several weeks +).
The next steps in the study include estimating thinning of the ice shelf that may have occurred in recent decades and further investigating the history of the ice shelf extent by means of potentially available aerial imagery from the early-mid 1900s.
Jack Landy: Exploiting a growing fleet of satellite altimeters to gain new perspectives on the Arctic’s ocean and ice cover
A wave of new polar-orbiting satellite altimetry missions is allowing us to view the Arctic ocean and sea ice cover at unprecedented detail. ESA’s Cryosat-2 has been operating since 2010, NASA’s ICESat-2 was launched in 2018, and the dual-frequency Earth Explorer mission CRISTAL (Copernicus Polar Ice and Snow Topography Altimeter) has recently been approved by the European Commission. In this talk I’ll introduce new modelling approaches for simulating the backscattered SAR altimeter echo waveform from polar ocean and snow-covered sea ice. This model has been applied to develop novel Arctic sea ice thickness retrievals from CryoSat-2, and is currently being exploited in the generation of multi-mission ice freeboard and snow depth-on-sea ice data products for the ESA “Polar+ Snow” Project. I’ll finally provide preliminary results for separating the thermodynamic from the dynamic terms of the winter sea ice volume growth budget, using the waveform model-based CryoSat-2 data.