Biogeochemical cycling of cadmium isotopes along a high-resolution section through the North Atlantic Ocean

2015 ◽  
Vol 148 ◽  
pp. 269-283 ◽  
Author(s):  
Tim M. Conway ◽  
Seth G. John
Keyword(s):  
High Resolution ◽  
Atlantic Ocean ◽  
North Atlantic ◽  
North Atlantic Ocean ◽  
Biogeochemical Cycling ◽  
The North ◽  
The North Atlantic

scholarly journals Early-Holocene simulations using different forcings and resolutions in AWI-ESM

The Holocene ◽  
2020 ◽  
Vol 30 (7) ◽  
pp. 996-1015 ◽  
Author(s):  
Xiaoxu Shi ◽  
Gerrit Lohmann ◽  
Dmitry Sidorenko ◽  
Hu Yang
Keyword(s):  
High Resolution ◽  
Atlantic Ocean ◽  
North Atlantic ◽  
North Atlantic Ocean ◽  
Ice Sheet ◽  
Meridional Overturning Circulation ◽  
Early Holocene ◽  
Glacial Meltwater ◽  
The North ◽  
The North Atlantic

The earliest part of the Holocene, from 11.5k to 7k (k = 1000 years before present), is a critical transition period between the relatively cold last deglaciation and the warm middle Holocene. It is marked by more pronounced seasonality and reduced greenhouse gases (GHGs) than the present state, as well as by the presence of the Laurentide Ice Sheet (LIS) and glacial meltwater perturbation. This paper performs experiments under pre-industrial and different early-Holocene regimes with AWI-ESM (Alfred Wegener Institute–Earth System Model), a state-of-the-art climate model with unstructured mesh and varying resolutions, to examine the sensitivity of the simulated Atlantic meridional overturning circulation (AMOC) to early-Holocene insolation, GHGs, topography (including properties of the ice sheet), and glacial meltwater perturbation. In the experiments with early-Holocene Earth orbital parameters and GHGs applied, the AWI-ESM simulation shows a JJA (June–July–August) warming and DJF (December–January–February) cooling over the mid and high latitudes compared with pre-industrial conditions, with amplification over the continents. The presence of the LIS leads to an additional regional cooling over the North America. We also simulate the meltwater event around 8.2k. Big discrepancies are found in the oceanic responses to different locations and magnitudes of freshwater discharge. Our experiments, which compare the effects of freshwater release evenly across the Labrador Sea to a more precise injection along the western boundary of the North Atlantic (the coastal region of LIS), show significant differences in the ocean circulation response, as the former produces a major decline of the AMOC and the latter yields no obvious effect on the strength of the thermohaline circulation. Furthermore, proglacial drainage of Lakes Agassiz and Ojibway leads to a fast spin-down of the AMOC, followed, however, by a gradual recovery. Most hosing experiments lead to a warming over the Nordic Sea and Barents Sea of varying magnitudes, because of an enhanced inflow from lower latitudes and a northward displacement of the North Atlantic deep convection. These processes exist in both of our high- and low-resolution experiments, but with some local discrepancies such as (1) the hosing-induced subpolar warming is much less pronounced in the high-resolution simulations; (2) LIS coastal melting in the high-resolution model leads to a slight decrease in the AMOC; and (3) the convection formation site in the low- and high-resolution experiments differs, in the former mainly over northeastern North Atlantic Ocean, but in the latter over a very shallow subpolar region along the northern edge of the North Atlantic Ocean. In conclusion, we find that our simulations capture spatially heterogeneous responses of the early-Holocene climate.

Seismic stratigraphy of the Vendean-Armorican platform of the French Atlantic shelf: new insights into the history of the North Atlantic ocean

2010 ◽  
Vol 181 (1) ◽  
pp. 37-50
Author(s):  
Pedro Huerta ◽  
Jean-Noël Proust ◽  
Pol Guennoc ◽  
Isabelle Thinon
Keyword(s):  
High Resolution ◽  
Atlantic Ocean ◽  
Sea Level ◽  
North Atlantic ◽  
North Atlantic Ocean ◽  
Passive Margin ◽  
Tectonic Activity ◽  
Marine Deposits ◽  
The North ◽  
The North Atlantic

Abstract The evolution of the North-Atlantic Ocean from its rifting stage during the Upper Jurassic until the present-day passive margin is recorded by the sedimentary wedge of eastern French-Atlantic platform. The study of a dense network of high resolution seismic profiles on the Vendean-Armorican platform (VAP) obtained during INSU-CNRS cruise “Geovend”, led to the characterization of the architecture of the sediment wedge preserved between the coast and Armorican margin shelf edge. This sediment wedge lies on a substratum composed of metamorphic and magmatic rocks of Palaeozoic age (Ub). The sediment wedge comprises six seismic units (U1-U6) bounded by regional unconformities: Jurassic marine succession (U1), Upper Cretaceous marine rocks (U2), Eocene-Oligocene marine deposits of the incipient VAP (U3), Miocene (U4) and Plio-Quaternary (U5) marine deposits overlain by the last sea-level rise ravinement deposits (U6). Above the basal unconformity at the top of Ub, the units are bounded by angular unconformities (top of U1, U2, U3), truncation with channel incision (top U4) or planar marine ravinement (top of U5) surfaces. Most of these unconformities are due to the tectonic activity of the bay of Biscay during the Mesozoic including (1) the North Atlantic rifting during the Jurassic to Early Cretaceous, (2) the propagation of the ocean crust and counterclockwise rotation of the Iberian block during the Aptian-Albian to Coniacian (magnetic anomaly 33–34) producing troughs at the top of U1 filled by downlapping U2 sediment wedges, (3) the Alpine compression at the origin of folding and faulting and the unconformable deposition of U3, and (4) the late compressive deformation during the Miocene that affected U4. The VAP acquires its actual configuration during U4. Sedimentation on the platform was then affected by climatically-controlled relative sea-level changes (U5 to U6) that forced U5 shelf margin sediment deposition above an incised unconformity and subsequently overlain by U6 transgressive sediment blanketing. One of the main interest of the VAP area is the existence of pre- to post-rift units that helps to decipher with high resolution seismics the long-lived evolution of the Armorican margin. Such units are preserved because of the specific characters of this area located on the flank of the former Aquitaine basin (near the “celtaquitaine” flexure) and the presence of the Rochebonne basement high. The VAP thus displays most of the tectonosedimentary evolution of the West Atlantic margins. This paper would however constitute a basis for comparisons to other examples around the Atlantic ocean and then contribute to strengthen the running models of passive margin evolution.

Sign in / Sign up

Export Citation Format

Share Document