scholarly journals North Atlantic Ice-Rafting: A Major Change at 75,000 Years Before the Present

Science ◽  
1977 ◽  
Vol 196 (4295) ◽  
pp. 1231-1231
Author(s):  
N. C. NEGUS ◽  
P. J. BERGER
Keyword(s):  
North Atlantic ◽  
Major Change ◽  
Ice Rafting

scholarly journals Change in the North Atlantic circulation associated with the mid-Pleistocene transition

2018 ◽  
Vol 14 (11) ◽  
pp. 1639-1651 ◽  
Author(s):  
Gloria M. Martin-Garcia ◽  
Francisco J. Sierro ◽  
José A. Flores ◽  
Fátima Abrantes
Keyword(s):  
North Atlantic ◽  
Major Change ◽  
Water Masses ◽  
Meridional Overturning Circulation ◽  
The Arctic ◽  
North Atlantic Current ◽  
The North ◽  
Oceanic Fronts ◽  
Surface Circulation ◽  
The North Atlantic

Abstract. The southwestern Iberian margin is highly sensitive to changes in the distribution of North Atlantic currents and to the position of oceanic fronts. In this work, the evolution of oceanographic parameters from 812 to 530 ka (MIS20–MIS14) is studied based on the analysis of planktonic foraminifer assemblages from site IODP-U1385 (37∘34.285′ N, 10∘7.562′ W; 2585 m b.s.l.). By comparing the obtained results with published records from other North Atlantic sites between 41 and 55∘ N, basin-wide paleoceanographic conditions are reconstructed. Variations of assemblages dwelling in different water masses indicate a major change in the general North Atlantic circulation during MIS16, coinciding with the definite establishment of the 100 ky cyclicity associated with the mid-Pleistocene transition. At the surface, this change consisted in the redistribution of water masses, with the subsequent thermal variation, and occurred linked to the northwestward migration of the Arctic Front (AF), and the increase in the North Atlantic Deep Water (NADW) formation with respect to previous glacials. During glacials prior to MIS16, the NADW formation was very weak, which drastically slowed down the surface circulation; the AF was at a southerly position and the North Atlantic Current (NAC) diverted southeastwards, developing steep south–north, and east–west, thermal gradients and blocking the arrival of warm water, with associated moisture, to high latitudes. During MIS16, the increase in the meridional overturning circulation, in combination with the northwestward AF shift, allowed the arrival of the NAC to subpolar latitudes, multiplying the moisture availability for ice-sheet growth, which could have worked as a positive feedback to prolong the glacials towards 100 ky cycles.

scholarly journals First monk seal from the Southern Hemisphere rewrites the evolutionary history of true seals

2020 ◽  
Vol 287 (1938) ◽  
pp. 20202318
Author(s):  
James P. Rule ◽  
Justin W. Adams ◽  
Felix G. Marx ◽  
Alistair R. Evans ◽  
Alan J. D. Tennyson ◽  
...  
Keyword(s):  
Southern Hemisphere ◽  
North Atlantic ◽  
Marine Mammals ◽  
Evolutionary History ◽  
Major Change ◽  
The North ◽  
History Of ◽  
Entire History ◽  
The North Atlantic ◽  
Monk Seals

Living true seals (phocids) are the most widely dispersed semi-aquatic marine mammals, and comprise geographically separate northern (phocine) and southern (monachine) groups. Both are thought to have evolved in the North Atlantic, with only two monachine lineages—elephant seals and lobodontins—subsequently crossing the equator. The third and most basal monachine tribe, the monk seals, have hitherto been interpreted as exclusively northern and (sub)tropical throughout their entire history. Here, we describe a new species of extinct monk seal from the Pliocene of New Zealand, the first of its kind from the Southern Hemisphere, based on one of the best-preserved and richest samples of seal fossils worldwide. This unanticipated discovery reveals that all three monachine tribes once coexisted south of the equator, and forces a profound revision of their evolutionary history: rather than primarily diversifying in the North Atlantic, monachines largely evolved in the Southern Hemisphere, and from this southern cradle later reinvaded the north. Our results suggest that true seals crossed the equator over eight times in their history. Overall, they more than double the age of the north–south dichotomy characterizing living true seals and confirms a surprisingly recent major change in southern phocid diversity.

Sea surface temperatures and ice rafting in the Holocene North Atlantic: climate influences on northern Europe and Greenland

2004 ◽  
Vol 23 (20-22) ◽  
pp. 2113-2126 ◽  
Author(s):  
Matthias Moros ◽  
Kay Emeis ◽  
Bjørg Risebrobakken ◽  
Ian Snowball ◽  
Antoon Kuijpers ◽  
...  
Keyword(s):  
North Atlantic ◽  
Sea Surface ◽  
Northern Europe ◽  
Sea Surface Temperatures ◽  
The Holocene ◽  
Surface Temperatures ◽  
North Atlantic Climate ◽  
Climate Influences ◽  
Ice Rafting

scholarly journals Predictable Climate Impacts of the Decadal Changes in the Ocean in the 1990s

2013 ◽  
Vol 26 (17) ◽  
pp. 6329-6339 ◽  
Author(s):  
Jon Robson ◽  
Rowan Sutton ◽  
Doug Smith
Keyword(s):  
North America ◽  
North Atlantic ◽  
Major Change ◽  
Climate Impacts ◽  
First Year ◽  
Prediction System ◽  
The North ◽  
Surface Climate ◽  
Before And After ◽  
Dry Conditions

Abstract During the 1990s there was a major change in the state of the world's oceans. In particular, the North Atlantic underwent a rapid warming, with sea surface temperatures (SSTs) in the subpolar gyre region increasing by 1°C in just a few years. Associated with the changes in SST patterns were changes in the surface climate, in particular, a tendency for warm and dry conditions over areas of North America in all seasons, and warm springs and wet summers over areas of Europe. Here, the extent to which a climate prediction system initialized using observations of the ocean state is able to capture the observed changes in seasonal mean surface climate is investigated. Rather than examining predictions of the mid-1990s North Atlantic warming event itself, this study compares hindcasts started before and after the warming, relative to hindcasts that do not assimilate information. It is demonstrated that the hindcasts capture many aspects of the observed changes in seasonal mean surface climate, especially in North, South, and Central America and in Europe. Furthermore, the prediction system retains skill beyond the first year. Finally, it is shown that, in addition to memory of Atlantic SSTs, successfully predicting Pacific SSTs was likely important for the hindcasts to predict surface climate over North America.

scholarly journals A low threshold for North Atlantic ice rafting from “low-slung slippery” late Pliocene ice sheets

2010 ◽  
Vol 25 (1) ◽  
Author(s):  
Ian Bailey ◽  
Clara T. Bolton ◽  
Robert M. DeConto ◽  
David Pollard ◽  
Ralf Schiebel ◽  
...  
Keyword(s):  
North Atlantic ◽  
Ice Sheets ◽  
Late Pliocene ◽  
Low Threshold ◽  
Ice Rafting

scholarly journals Timing of iceberg scours and massive ice-rafting events in the subtropical North Atlantic

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Alan Condron ◽  
Jenna C. Hill
Keyword(s):  
North Atlantic ◽  
Sediment Cores ◽  
Eastern United States ◽  
Deep Water Formation ◽  
Seafloor Mapping ◽  
Heinrich Event ◽  
Freshwater Forcing ◽  
Water Formation ◽  
Cape Hatteras ◽  
Ice Rafting

AbstractHigh resolution seafloor mapping shows extraordinary evidence that massive (>300 m thick) icebergs once drifted >5,000 km south along the eastern United States, with >700 iceberg scours now identified south of Cape Hatteras. Here we report on sediment cores collected from several buried scours that show multiple plow marks align with Heinrich Event 3 (H3), ~31,000 years ago. Numerical glacial iceberg simulations indicate that the transport of icebergs to these sites occurs during massive, but short-lived, periods of elevated meltwater discharge. Transport of icebergs to the subtropics, away from deep water formation sites, may explain why H3 was associated with only a modest increase in ice-rafting across the subpolar North Atlantic, and implies a complex relationship between freshwater forcing and climate change. Stratigraphy from subbottom data across the scour marks shows there are additional features that are both older and younger, and may align with other periods of elevated meltwater discharge.

Sign in / Sign up

Export Citation Format

Share Document