DSpace Collection:

Melt Pond Mapping With High-Resolution SAR: The First View

2022-03-24T07:11:37Z

Title: Melt Pond Mapping With High-Resolution SAR: The First View Authors: Kim, Duk-Jin; Moon, Wooil M.; Jung, Hyung-Sup; Lee, Sang H.; Chung, Kyung Ho; Hwang, Byongjun Abstract: Melt pond statistics (size and shape) have previously been retrieved from aerial photography and high-resolution visible satellite data. These submeter- or meter resolution visible data can provide reasonably accurate information on melt ponds, but are greatly constrained by the limited solar illumination and frequent cloud cover in the Arctic region. In this study, we venture into exploring high-resolution synthetic aperture radar (SAR) or imaging radar method for melt pond mapping, which is not severely disrupted by cloud or low solar zenith angle. We analyzed high- resolution airborne SAR images (0.3-m resolution) of midsummer sea ice, acquired from a helicopter- borne SAR system in the northern Chuchi Sea. The pond area and shape (circularity) derived from the airborne SAR images showed that the statistics were comparable to those previously observed from aerial photographs. We argue that high-resolution SAR, together with one-to-one comparison with coincident aerial photographs, can be used to map melt ponds at the level of detail comparable to aerial photography or high-resolution optical satellite remote sensing. Our encouraging results suggest the possibility of using high-resolution SAR (current or future systems) to map melt ponds in the Arctic region.t ponds, but are greatly constrained by the limited solar illumination and frequent cloud cover in the Arctic region. In this study, we venture into exploring high-resolution synthetic aperture radar (SAR) or imaging radar method for melt pond mapping, which is not severely disrupted by cloud or low solar zenith angle. We analyzed high- resolution airborne SAR images (0.3-m resolution) of midsummer sea ice, acquired from a helicopter- borne SAR system in the northern Chuchi Sea. The pond area and shape (circularity) derived from the airborne SAR images showed that the statistics were comparable to those previously observed from aerial photographs. We argue that high-resolution SAR, together with one-to-one comparison with coincident aerial photographs, can be used to map melt ponds at the level of detail comparable to aerial photography or high-resolution optical satellite remote sensing. Our encouraging results suggest the possibility of using high-resolution SAR (current or future systems) to map melt ponds in the Arctic region.

Spatial distribution of phytoplankton productivity in the Amundsen Sea, Antarctica

2022-03-24T07:10:48Z

Title: Spatial distribution of phytoplankton productivity in the Amundsen Sea, Antarctica Authors: Lee, Sang Heon; Joo, HuiTae; Lee, Sang H.; Yun, Mi Sun; Shin, Hyoung Chul; Kim, Young Nam; Yang, Eun Jin; Kim, Bo Kyung Abstract: To date, no direct measurements of primary production were taken in the Amundsen Sea, which is one of the highest primary productivity regions in the Antarctic. Phytoplankton carbon and nitrogen uptake experiments were conducted at 16 selected stations using a 13C？15N dual isotope tracer technique. We found no statistically significant depletions of major inorganic nutrients (nitrate + nitrite, ammonium, and silicate) although the concentrations of these nutrients were markedly reduced in the surface layer of the polynya stations where large celled phytoplankton (>20 μm) predominated (ca. 64 %). The average chl-a concentration was significantly higher at polynya stations than at non-polynya stations (p < 0.01). Average daily carbon and nitrogen uptake rates by phytoplankton at polynya stations were 2.2 g C m？2 day？1 (SD = ±1.4 g C m？2 day？1) and 0.9 g N m？2 day？1 (SD = ±0.2 g N m？2 day？1), respectively, about 5？10 times higher than those at non-polynya stations. These ranges are as high as those in the Ross Sea, which has the highest productivity among polynyas in the Antarctic Ocean. The unique productivity patterns in the Amundsen Sea are likely due to differences in iron limitation, phytoplankton productivity, the timing of phytoplankton growing season, or a combination of these factors.

Copepod feeding in a coastal area of active tidal mixing: diel and monthly variations of grazing impacts on phytoplankton biomass

2022-03-24T07:11:37Z

Title: Copepod feeding in a coastal area of active tidal mixing: diel and monthly variations of grazing impacts on phytoplankton biomass Authors: Lee, Doo Byoul; Song, Hye Y.; Choi, Keun H.; Park, Chul Abstract: This study examined monthly feeding rates and grazing impact on phytoplankton biomass, as well as diel feeding rhythms of four key copepod species in a tidally well mixed estuary (Asan Bay, Korean Peninsula). Monthly ingestion rates estimated based on gut pigment analysis were closely associated with their peak densities, but not with phytoplankton biomass, implying high ingestion may be related to reproductive output for population growth. The three smaller copepods, Acartia hongi, Acartia pacifica and Paracalanus parvus, showed feeding preference for smaller phytoplankton (

Circumpolar Deep Water (CDW) intrusion over the continental shelf in the Amundsen Sea.

2022-03-24T07:13:27Z

Title: Circumpolar Deep Water (CDW) intrusion over the continental shelf in the Amundsen Sea. Authors: Ha, Ho Kyung; Rhee, Tae Siek; Lee, Sang H.; Shin, Hyoung Chul; Hahm, Doshik Abstract: The Amundsen Sea sector is the most rapidly changing region of the Antarctic ice sheets. It has been claimed that the rapid retreat of the glaciers (or ice sheets) is primarily related to the intrusion of warm Circumpolar Deep Water (CDW) which acts as an oceanic heat source. The Amundsen shelf troughs were suspected to be main conduits supplying warm CDW onto the continental shelf, eroding the underside of the ice sheets and glaciers. Despite the critical role of CDW in the continental shelf of the Amundsen Sea, vital information is still absent from the existing body of knowledge pertaining to spatial-temporal variability of CDW. This is mainly because the Amundsen Sea is remotely located and the extremely harsh weather and sea conditions limited the access to its inner shelf. Lack of data hindered our evaluation and prediction of physical processes and associated biogeochemical processes in the Amundsen Sea. Using the icebreaker R/V Araon, a multi-disciplinary scientific cruise was conducted between December, 2010 and January, 2011 to timely address these processes. During the expedition, total 30 CTD stations were visited. It was observed that the warm CDW occupied a large volume off the continental slope. As it was transported onto the continental shelf, it was modified (i.e., cooled and freshened) to be modified CDW (MCDW) by interacting with Antarctic Surface Water. Two crosW) which acts as an oceanic heat source. The Amundsen shelf troughs were suspected to be main conduits supplying warm CDW onto the continental shelf, eroding the underside of the ice sheets and glaciers. Despite the critical role of CDW in the continental shelf of the Amundsen Sea, vital information is still absent from the existing body of knowledge pertaining to spatial-temporal variability of CDW. This is mainly because the Amundsen Sea is remotely located and the extremely harsh weather and sea conditions limited the access to its in