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Author Bashmachnikov, I.L.; Fedorov, A.M.; Vesman, A.V.; Belonenko, T.V.; Dukhovskoy, D.S.
Title Thermohaline convection in the subpolar seas of the North Atlantic from satellite and in situ observations. Part 2: indices of intensity of deep convection Type $loc['typeJournal Article']
Year 2019 Publication Abbreviated Journal
Volume 16 Issue 1 Pages 191-201
Keywords deep convection, assimilation of satellite data, altimetry, water density, the Greenland Sea, the Labrador Sea, the Irminger Sea
Abstract Variation in locations of the maximum development of deep convection in the subpolar seas, taking into account their small dimensions, represent difficulty in identifying its interannual variability from usually sparse in situ data. In this work, the interannual variability of the maximum convection depth, is obtained using one of the most complete datasets ARMOR, which combines in situ and satellite data. The convection depths, derived from ARMOR, are used for testing the efficiency of two indices of convection intensity: (1) sea-level anomalies from satellite altimetry and (2) the integral water density in the areas of the most frequent development of deep convection. The first index, capturing some details, shows low correlations with the interannual variability of the deep convection intensity. The second index shows high correlation with the deep convection intensity in the Greenland, Irminger and Labrador seas. Asynchronous variations in the deep convection intensity in the Labrador-Irminger seas and in the Greenland Sea are obtained. In the Labrador and in the Irminger seas, the quasi-seven-year variations in the convection intensity are identified.
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Call Number COAPS @ user @ Serial 1089
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Author Deng, J.; Wu, Z.; Zhang, M.; Huang, N.E.; Wang, S.; Qiao, F.
Title Using Holo-Hilbert spectral analysis to quantify the modulation of Dansgaard-Oeschger events by obliquity Type $loc['typeJournal Article']
Year 2018 Publication Quaternary Science Reviews Abbreviated Journal Quaternary Science Reviews
Volume 192 Issue Pages 282-299
Keywords Pleistocene; Paleoclimatology; Greenland; Antarctica; Data treatment; Data analysis; Dansgaard-oeschger (DO) events; Obliquity forcing; Phase preference; Holo-hilbert spectral analysis; Amplitude modulation; EMPIRICAL MODE DECOMPOSITION; GREENLAND ICE-CORE; NONSTATIONARY TIME-SERIES; ABRUPT CLIMATE-CHANGE; LAST GLACIAL PERIOD; NORTH-ATLANTIC; MILLENNIAL-SCALE; RECORDS; VARIABILITY; CYCLE
Abstract Astronomical forcing (obliquity and precession) has been thought to modulate Dansgaard-Oeschger (DO) events, yet the detailed quantification of such modulations has not been examined. In this study, we apply the novel Holo-Hilbert Spectral Analysis (HHSA) to five polar ice core records, quantifying astronomical forcing's time-varying amplitude modulation of DO events and identifying the preferred obliquity phases for large amplitude modulations. The unique advantages of HHSA over the widely used windowed Fourier spectral analysis for quantifying astronomical forcing's nonlinear modulations of DO events is first demonstrated with a synthetic data that closely resembles DO events recorded in Greenland ice cores (NGRIP, GRIP, and GISP2 cores on GICC05 modelext timescale). The analysis of paleoclimatic proxies show that statistically significantly more frequent DO events, with larger amplitude modulation in the Greenland region, tend to occur in the decreasing phase of obliquity, especially from its mean value to its minimum value. In the eastern Antarctic, although statistically significantly more DO events tend to occur in the decreasing obliquity phase in general, the preferred phase of obliquity for large amplitude modulation on DO events is a segment of the increasing phase near the maximum obliquity, implying that the physical mechanisms of DO events may be different for the two polar regions. Additionally, by using cross-spectrum and magnitude-squared analyses, Greenland DO mode at a timescale of about 1400 years leads the Antarctic DO mode at the same timescale by about 1000 years. (C) 2018 Elsevier Ltd. All rights reserved.
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ISSN 0277-3791 ISBN Medium
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Funding Approved $loc['no']
Call Number COAPS @ user @ Serial 971
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Author Dukhovskoy, D.S.; Myers, P.G.; Platov, G.; Timmermans, M.-L.; Curry, B.; Proshutinsky, A.; Bamber, J.L.; Chassignet, E.; Hu, X.; Lee, C.M.; Somavilla, R.
Title Greenland freshwater pathways in the sub-Arctic Seas from model experiments with passive tracers Type $loc['typeJournal Article']
Year 2016 Publication Journal of Geophysical Research: Oceans Abbreviated Journal J. Geophys. Res. Oceans
Volume 121 Issue 1 Pages 877-907
Keywords Greenland Ice Sheet melting; Greenland freshwater; thermohaline circulation; Nordic Seas; sub-Arctic seas; Baffin Bay; Labrador Sea
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Series Editor Series Title Abbreviated Series Title
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ISSN 2169-9275 ISBN Medium
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Call Number COAPS @ mfield @ Serial 35
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Author Dukhovskoy, D.S.; Yashayaev, I.; Proshutinsky, A.; Bamber, J.L.; Bashmachnikov, I.L.; Chassignet, E.P.; Lee, C.M.; Tedstone, A.J.
Title Role of Greenland Freshwater Anomaly in the Recent Freshening of the Subpolar North Atlantic Type $loc['typeJournal Article']
Year 2019 Publication Journal of Geophysical Research: Oceans Abbreviated Journal J. Geophys. Res. Oceans
Volume 124 Issue 5 Pages 3333-3360
Keywords Greenland ice sheet melting; freshwater anomaly; subpolar North Atlantic; subpolar gyre; passive tracer numerical experiment; freshwater budget
Abstract The cumulative Greenland freshwater flux anomaly has exceeded 5000 km3 since the 1990s. The volume of this surplus fresh water is expected to cause substantial freshening in the North Atlantic. Analysis of hydrographic observations in the subpolar seas reveal freshening signals in the 2010s. The sources of this freshening are yet to be determined. In this study, the relationship between the surplus Greenland freshwater flux and this freshening is tested by analyzing the propagation of the Greenland freshwater anomaly and its impact on salinity in the subpolar North Atlantic based on observational data and numerical experiments with and without the Greenland runoff. A passive tracer is continuously released during the simulations at freshwater sources along the coast of Greenland to track the Greenland freshwater anomaly. Tracer budget analysis shows that 44% of the volume of the Greenland freshwater anomaly is retained in the subpolar North Atlantic by the end of the simulation. This volume is sufficient to cause strong freshening in the subpolar seas if it stays in the upper 50�100 m. However, in the model the anomaly is mixed down to several hundred meters of the water column resulting in smaller magnitudes of freshening compared to the observations. Therefore, the simulations suggest that the accelerated Greenland melting would not be sufficient to cause the observed freshening in the subpolar seas and other sources of fresh water have contributed to the freshening. Impacts on salinity in the subpolar seas of the freshwater transport through Fram Strait and precipitation are discussed.
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Corporate Author Thesis
Publisher Place of Publication Editor
Language Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 2169-9275 ISBN Medium
Area Expedition Conference
Funding Approved $loc['no']
Call Number COAPS @ user @ Serial 1029
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