| Paper: | TH-A1.15 |
| Session: | Applications of Radiometry I |
| Time: | Thursday, March 29, 09:00 - 10:20 |
| Presentation: |
Poster
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| Topic: |
Theory, physical principles and electromagnetic models: |
| Title: |
Airborne Observation of Firn Aquifers on the Sukkertoppen Ice Cap, Greenland using the Ultra-Wideband Software Defined Microwave Radiometer (UWBRAD) |
| Authors: |
Julie Miller; The Ohio State University | | |
| | Joel Johnson; The Ohio State University | | |
| | Kenneth Jezek; The Ohio State University | | |
| | Alexandra Bringer; The Ohio State University | | |
| | Mark Andrews; The Ohio State University | | |
| | Dominique Belgiovane; The Ohio State University | | |
| Abstract: |
The recent discovery of firn aquifers (layers of water-saturated coarse-grained snow buried as deep as a few tens of meters below the surface) within the Greenland Ice Sheet and its peripheral ice caps has changed long-held assumptions about the longevity of liquid meltwater following summer surface melting in ice sheet-systems, and opened up exciting new areas of research. Retaining liquid meltwater in this way has potential impacts on ice flow, sea level, and ice core records, and the significance of firn aquifers in climate–ice interactions is currently being explored.
We are developing passive microwave retrieval techniques to map firn aquifer areas on ice sheets and ice caps using L-band microwave radiometry. Given that L-band emissions are capable of penetrating thorough snow, firn, and ice from tens to hundreds of meters below the surface, and that brightness temperature is extremely sensitive to the presence liquid meltwater, these instruments provide an innovative observational tool for mapping firn aquifer parameters. Our current retrieval technique exploits satellite L-band brightness temperature time series to map firn aquifer spatial extent.
Here, we will present analysis of novel new airborne multi-frequency L-band (0.5-2 GHz) brightness temperature data recently collected over the Sukkertoppen Ice Cap off the coast of the western Greenland Ice Sheet together with satellite firn aquifer retreivals generated from new enhanced resolution L-band (1.4 GHz) brightness temperature data. The Ultra-Wideband Software-Defined Microwave Radiometer (UWBRAD) was developed at Ohio State University under the support of NASA’s Instrument Incubator Program. UWBRAD was operated aboard a DC-3 aircraft chartered from Kenn Borek Airlines, and deployed in Greenland in Septmeber 2017. Multi-frequency L-band brightness temperature was collected over the Sukkertoppen Ice Cap along flight lines where firn aquifers areas have previously been mapped using repeat airborne radar surveys collected by NASA’s Operation IceBridge campaign. The DC-3 was flown at a height of ~500 m above the ice cap surface which resulted in a spatial resolution of ~3.5 km. Enhanced resolution L-band brightness temperature time series are currently being generated from data collected by the microwave radiometer aboard the Soil Moisture Active Passive (SMAP) satellite as part of the NASA MEaSUREs Calibrated Passive Microwave Daily EASE Grid 2.0 Brightness Temperature (CETB) Earth System Data Record (ESDR) project. The resolution enhancement technique improves the relatively coarse spatial resolution of SMAP data (~36 km) to a spatial resolution comparable to UWBRAD data (~3 km). Comparisons will be made between airborne data and satellite time series data. Distinct L-band spectral signatures exhibited by airborne data will be identified, and then validated using simple physics-based electromagnetic forward modeling. The presentation will conclude by discussing the potential for mapping firn aquifer areas on ice sheets and ice caps using L-band spectral signatures.
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