English
norskBlar i forfatter "Ezat, Mohamed"
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Deep ocean 14C ventilation age reconstructions from the Arctic Mediterranean reassessed
(Journal article; Tidsskriftartikkel; Peer reviewed, 2019-05-13)The present-day ocean ventilation in the Arctic Mediterranean (Nordic Seas and Arctic Ocean), via transformation of northward inflowing warm Atlantic surface water into cold deep water, affects regional climate, atmospheric circulation and carbon storage in the deep ocean. Here we study the glacial evolution of the Arctic Mediterranean circulation and its influence on glacial climate using ... -
Deep ocean storage of heat and CO2 in the Fram Strait, Arctic Ocean during the last glacial period
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-07-19)The Fram Strait is the only deep gateway between the Arctic Ocean and the Nordic Seas and thus is a key area to study past changes in ocean circulation and the marine carbon cycle. Here, we study deep ocean temperature, δ18O, carbonate chemistry (i.e., carbonate ion concentration [CO32−]), and nutrient content in the Fram Strait during the late glacial (35,000–19,000 years BP) and the Holocene based ... -
Deglacial bottom water warming intensified Arctic methane seepage in the NW Barents Sea
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-09-09)Changes in the Arctic climate-ocean system can rapidly impact carbon cycling and cryosphere. Methane release from the seafloor has been widespread in the Barents Sea since the last deglaciation, being closely linked to changes in pressure and bottom water temperature. Here, we present a post-glacial bottom water temperature record (18,000–0 years before present) based on Mg/Ca in benthic foraminifera ... -
Episodic release of CO2 from the high-latitude North Atlantic Ocean during the last 135 kyrs
(Journal article; Tidsskriftartikkel; Peer reviewed, 2017-02-22)Antarctic ice cores document glacial-interglacial and millennial-scale variability in atmospheric pCO2 over the past 800 kyr. The ocean, as the largest active carbon reservoir on this timescale, is thought to have played a dominant role in these pCO2 fluctuations, but it remains unclear how and where in the ocean CO2 was stored during glaciations and released during (de)glacial millennial-scale ... -
Fast and slow components of interstadial warming in the North Atlantic during the last glacial
(Journal article; Tidsskriftartikkel; Peer reviewed, 2020-08-13)The abrupt nature of warming events recorded in Greenland ice-cores during the last glacial has generated much debate over their underlying mechanisms. Here, we present joint marine and terrestrial analyses from the Portuguese Margin, showing a succession of cold stadials and warm interstadials over the interval 35–57 ka. Heinrich stadials 4 and 5 contain considerable structure, with a short ... -
Millennial‐scale changes in bottom water temperature and water mass exchange through the Fram Strait 79ºN, 63–13 ka
(Journal article; Tidsskriftartikkel; Peer reviewed, 2020-12-31)The Svalbard margin, in the eastern Fram Strait with its high sediment accumulation, form a key area for the reconstruction of water mass and heat exchange between the North Atlantic and Arctic Ocean in relation to abrupt climate changes as seen in glacial Greenland Interstadial and Greenland Stadial (GI‐GS) events. Here, we present a bottom water temperature (BWT) record from the northern Nordic ... -
New Late Pleistocene species of Acharax from Arctic methane seeps off Svalbard
(Journal article; Tidsskriftartikkel; Peer reviewed, 2019-05-01)We report, for the first time, the solemyid <i>Acharax svalbardensis</i> sp. nov., from deep-sea methane seep sites on the western Svalbard margin, 79°N. This species is rather small and so far the northernmost representative of its genus. It is identified based on the following combination of diagnostic characters: umbo 27–30% valve length from posterior margin; H/L ratio ∼0.35; broadly rounded to ... -
Reconstruction of hydrographic changes in the southern Norwegian Sea during the past 135 kyr and the impact of different foraminiferal Mg/Ca cleaning protocols
(Journal article; Tidsskriftartikkel; Peer reviewed, 2016-08-20)The shallow subsurface hydrography in the southern Norwegian Sea during the past 135,000 years was investigated using parallel measurements of Mg/Ca and δ18O in shells of the planktic foraminiferal species Neogloboquadrina pachyderma. Two cleaning methods were applied prior to Mg/Ca analysis, “Mg cleaning” and “full cleaning” methods. Different results were obtained, which are most likely due to a ... -
Sea ice and millennial-scale climate variability in the Nordic seas 90 kyr ago to present
(Journal article; Tidsskriftartikkel; Peer reviewed, 2016-07-26)In the light of rapidly diminishing sea ice cover in the Arctic during the present atmospheric warming, it is imperative to study the distribution of sea ice in the past in relation to rapid climate change. Here we focus on glacial millennial-scale climatic events (Dansgaard/Oeschger events) using the sea ice proxy IP25 in combination with phytoplankton proxy data and quantification of diatom species ... -
Ventilation History of the Nordic Seas Deduced from Pelagic‐Benthic Radiocarbon Age Offsets
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-03-24)Changes in ocean circulation are considered a major driver of centennial-to-millennial scale climate variability during the last deglaciation. Using four sediment records from the Nordic Seas, we studied radiocarbon ventilation ages in subsurface and bottom waters to reconstruct past variations in watermass overturning. Planktic foraminiferal ages show significant spatial variability over most of ...
