scholarly journals Regional seesaw between the North Atlantic and Nordic Seas during the last glacial abrupt climate events

2017 ◽  
Vol 13 (6) ◽  
pp. 729-739 ◽  
Author(s):  
Mélanie Wary ◽  
Frédérique Eynaud ◽  
Didier Swingedouw ◽  
Valérie Masson-Delmotte ◽  
Jens Matthiessen ◽  
...  
Keyword(s):  
Sea Ice ◽  
North Atlantic ◽  
Sea Surface ◽  
Nordic Seas ◽  
Norwegian Sea ◽  
Surface Conditions ◽  
Last Glacial ◽  
The North ◽  
The North Atlantic ◽  
The Last Glacial

Abstract. Dansgaard–Oeschger oscillations constitute one of the most enigmatic features of the last glacial cycle. Their cold atmospheric phases have been commonly associated with cold sea-surface temperatures and expansion of sea ice in the North Atlantic and adjacent seas. Here, based on dinocyst analyses from the 48–30 ka interval of four sediment cores from the northern Northeast Atlantic and southern Norwegian Sea, we provide direct and quantitative evidence of a regional paradoxical seesaw pattern: cold Greenland and North Atlantic phases coincide with warmer sea-surface conditions and shorter seasonal sea-ice cover durations in the Norwegian Sea as compared to warm phases. Combined with additional palaeorecords and multi-model hosing simulations, our results suggest that during cold Greenland phases, reduced Atlantic meridional overturning circulation and cold North Atlantic sea-surface conditions were accompanied by the subsurface propagation of warm Atlantic waters that re-emerged in the Nordic Seas and provided moisture towards Greenland summit.

scholarly journals Regional seesaw between North Atlantic and Nordic Seas during the last glacial abrupt climate events

2017 ◽  
Author(s):  
Mélanie Wary ◽  
Frédérique Eynaud ◽  
Didier Swingedouw ◽  
Valérie Masson-Delmotte ◽  
Jens Matthiessen ◽  
...  
Keyword(s):  
Sea Ice ◽  
North Atlantic ◽  
Meridional Overturning Circulation ◽  
Sea Surface ◽  
Glacial Cycle ◽  
Nordic Seas ◽  
Norwegian Sea ◽  
Surface Conditions ◽  
Last Glacial ◽  
The Last Glacial

Abstract. Dansgaard-Oeschger oscillations constitute one of the most enigmatic features of the last glacial cycle. Their cold atmospheric phases have been commonly associated with cold sea-surface temperatures and expansion of sea ice in the North Atlantic and adjacent seas. Here, based on dinocyst analyses from the 48–30 ka BP interval of four sediment cores from the northern Northeast Atlantic and southern Norwegian Sea, we provide direct and quantitative evidence of a regional paradoxical seesaw pattern: cold Greenland and North Atlantic phases coincide with warmer sea-surface conditions and shorter seasonal sea-ice cover durations in the Norwegian Sea as compared to warm phases. Combined with additional paleorecords and multi-model hosing simulations, our results suggest that during cold Greenland phases, reduced Atlantic meridional overturning circulation and cold North Atlantic sea-surface conditions were accompanied by the subsurface propagation of warm Atlantic waters that re-emerged in the Nordic Seas and provided moisture towards Greenland summit.

scholarly journals 120,000 year record of sea ice in the North Atlantic

2018 ◽  
Author(s):  
Niccolò Maffezzoli ◽  
Paul Vallelonga ◽  
Ross Edwards ◽  
Alfonso Saiz-Lopez ◽  
Clara Turetta ◽  
...  
Keyword(s):  
Sea Ice ◽  
North Atlantic ◽  
Arctic Sea Ice ◽  
Sea Ice Extent ◽  
Nordic Seas ◽  
Last Glacial ◽  
The North ◽  
Arctic Sea ◽  
The North Atlantic ◽  
The Last Glacial

Abstract. Although it has been demonstrated that the speed and magnitude of recent Arctic sea ice decline is unprecedented for the past 1,450 years, few records are available to provide a paleoclimate context for Arctic sea ice extent. Here we present a 120 kyr record of bromine enrichment from the RECAP ice core, coastal East Greenland, and reconstruct past sea ice conditions in the North Atlantic as far north as the entrance of the Arctic Ocean (50–85° N). Bromine enrichment has been previously employed to reconstruct first-year sea ice (FYSI) in the Canadian Arctic over the last glacial cycle. We find that during the last deglaciation, the transition from multi-year sea ice (MYSI) to FYSI started at ∼ 17.6 kyr, synchronous with sea ice reductions observed in the eastern Nordic seas (Müller and Stein, 2014; Hoff et al., 2016) and with the increase of North Atlantic ocean temperature (Dokken and Jansen, 1999). FYSI reached its maximum extent at 12.4–11.8 kyr, after which open-water conditions started to dominate, as supported by sea ice records from the eastern Nordic seas and the North Icelandic shelf. Our results show that over the last 120,000 years, sea ice extent was greatest during Marine Isotope Stage (MIS) 2 and MIS4, with decreased levels during MIS3 and the onset of the last glacial period (late-MIS5). Sea ice extent during the last 10 kyr (Holocene/MIS1) has been less than at any time in the last 120 kyr.

The Effect of a Large Freshwater Perturbation on the Glacial North Atlantic Ocean Using a Coupled General Circulation Model

2006 ◽  
Vol 19 (17) ◽  
pp. 4436-4447 ◽  
Author(s):  
C. D. Hewitt ◽  
A. J. Broccoli ◽  
M. Crucifix ◽  
J. M. Gregory ◽  
J. F. B. Mitchell ◽  
...  
Keyword(s):  
Sea Ice ◽  
North Atlantic ◽  
General Circulation ◽  
Circulation Model ◽  
Quasi Equilibrium ◽  
Last Glacial ◽  
Proxy Records ◽  
The North ◽  
The North Atlantic ◽  
The Last Glacial

Abstract The commonly held view of the conditions in the North Atlantic at the last glacial maximum, based on the interpretation of proxy records, is of large-scale cooling compared to today, limited deep convection, and extensive sea ice, all associated with a southward displaced and weakened overturning thermohaline circulation (THC) in the North Atlantic. Not all studies support that view; in particular, the “strength of the overturning circulation” is contentious and is a quantity that is difficult to determine even for the present day. Quasi-equilibrium simulations with coupled climate models forced by glacial boundary conditions have produced differing results, as have inferences made from proxy records. Most studies suggest the weaker circulation, some suggest little or no change, and a few suggest a stronger circulation. Here results are presented from a three-dimensional climate model, the Hadley Centre Coupled Model version 3 (HadCM3), of the coupled atmosphere–ocean–sea ice system suggesting, in a qualitative sense, that these diverging views could all have occurred at different times during the last glacial period, with different modes existing at different times. One mode might have been characterized by an active THC associated with moderate temperatures in the North Atlantic and a modest expanse of sea ice. The other mode, perhaps forced by large inputs of meltwater from the continental ice sheets into the northern North Atlantic, might have been characterized by a sluggish THC associated with very cold conditions around the North Atlantic and a large areal cover of sea ice. The authors’ model simulation of such a mode, forced by a large input of freshwater, bears several of the characteristics of the Climate: Long-range Investigation, Mapping, and Prediction (CLIMAP) Project’s reconstruction of glacial sea surface temperature and sea ice extent.

scholarly journals Evidence for strong relations between the upper Tagus loess formation (central Iberia) and the marine atmosphere off the Iberian margin during the last glacial period

2021 ◽  
pp. 1-30
Author(s):  
Daniel Wolf ◽  
Thomas Kolb ◽  
Karolin Ryborz ◽  
Susann Heinrich ◽  
Imke Schäfer ◽  
...  
Keyword(s):  
North Atlantic ◽  
Moisture Transfer ◽  
Sea Temperature ◽  
Last Glacial ◽  
Atmospheric Circulation Patterns ◽  
The North ◽  
Terrestrial Environments ◽  
The North Atlantic ◽  
Iberian Margin ◽  
The Last Glacial

Abstract During glacial times, the North Atlantic region was affected by serious climate changes corresponding to Dansgaard-Oeschger cycles that were linked to dramatic shifts in sea temperature and moisture transfer to the continents. However, considerable efforts are still needed to understand the effects of these shifts on terrestrial environments. In this context, the Iberian Peninsula is particularly interesting because of its close proximity to the North Atlantic, although the Iberian interior lacks paleoenvironmental information so far because suitable archives are rare. Here we provide an accurate impression of the last glacial environmental developments in central Iberia based on comprehensive investigations using the upper Tagus loess record. A multi-proxy approach revealed that phases of loess formation during Marine Isotope Stage (MIS) 2 (and upper MIS 3) were linked to utmost aridity, coldness, and highest wind strengths in line with the most intense Greenland stadials also including Heinrich Events 3–1. Lack of loess deposition during the global last glacial maximum (LGM) suggests milder conditions, which agrees with less-cold sea surface temperatures (SST) off the Iberian margin. Our results demonstrate that geomorphological system behavior in central Iberia is highly sensitive to North Atlantic SST fluctuations, thus enabling us to reconstruct a detailed hydrological model in relation to marine–atmospheric circulation patterns.

scholarly journals Timing and structure of the Younger Dryas event and its underlying climate dynamics

2020 ◽  
Vol 117 (38) ◽  
pp. 23408-23417
Author(s):  
Hai Cheng ◽  
Haiwei Zhang ◽  
Christoph Spötl ◽  
Jonathan Baker ◽  
Ashish Sinha ◽  
...  
Keyword(s):  
Southern Hemisphere ◽  
North Atlantic ◽  
Time Scale ◽  
Asian Monsoon ◽  
Younger Dryas ◽  
Tropical Pacific ◽  
Last Glacial ◽  
The North ◽  
The North Atlantic ◽  
The Last Glacial

The Younger Dryas (YD), arguably the most widely studied millennial-scale extreme climate event, was characterized by diverse hydroclimate shifts globally and severe cooling at high northern latitudes that abruptly punctuated the warming trend from the last glacial to the present interglacial. To date, a precise understanding of its trigger, propagation, and termination remains elusive. Here, we present speleothem oxygen-isotope data that, in concert with other proxy records, allow us to quantify the timing of the YD onset and termination at an unprecedented subcentennial temporal precision across the North Atlantic, Asian Monsoon-Westerlies, and South American Monsoon regions. Our analysis suggests that the onsets of YD in the North Atlantic (12,870 ± 30 B.P.) and the Asian Monsoon-Westerlies region are essentially synchronous within a few decades and lead the onset in Antarctica, implying a north-to-south climate signal propagation via both atmospheric (decadal-time scale) and oceanic (centennial-time scale) processes, similar to the Dansgaard–Oeschger events during the last glacial period. In contrast, the YD termination may have started first in Antarctica at ∼11,900 B.P., or perhaps even earlier in the western tropical Pacific, followed by the North Atlantic between ∼11,700 ± 40 and 11,610 ± 40 B.P. These observations suggest that the initial YD termination might have originated in the Southern Hemisphere and/or the tropical Pacific, indicating a Southern Hemisphere/tropics to North Atlantic–Asian Monsoon-Westerlies directionality of climatic recovery.

scholarly journals Connection between Sea Surface Anomalies and Atmospheric Quasi-Stationary Waves

2020 ◽  
Vol 33 (1) ◽  
pp. 201-212
Author(s):  
G. Wolf ◽  
A. Czaja ◽  
D. J. Brayshaw ◽  
N. P. Klingaman
Keyword(s):  
Sea Ice ◽  
North Atlantic ◽  
Southern Oscillation ◽  
Late Summer ◽  
Ice Cover ◽  
Sea Surface ◽  
Late Winter ◽  
Driving Mechanism ◽  
The North ◽  
The North Atlantic

AbstractLarge-scale, quasi-stationary atmospheric waves (QSWs) are known to be strongly connected with extreme events and general weather conditions. Yet, despite their importance, there is still a lack of understanding about what drives variability in QSW. This study is a step toward this goal, and it identifies three statistically significant connections between QSWs and sea surface anomalies (temperature and ice cover) by applying a maximum covariance analysis technique to reanalysis data (1979–2015). The two most dominant connections are linked to El Niño–Southern Oscillation and the North Atlantic Oscillation. They confirm the expected relationship between QSWs and anomalous surface conditions in the tropical Pacific and the North Atlantic, but they cannot be used to infer a driving mechanism or predictability from the sea surface temperature or the sea ice cover to the QSW. The third connection, in contrast, occurs between late winter to early spring Atlantic sea ice concentrations and anomalous QSW patterns in the following late summer to early autumn. This new finding offers a pathway for possible long-term predictability of late summer QSW occurrence.

scholarly journals Polymastiidae (Porifera: Demospongiae) of the Nordic and Siberian Seas

2017 ◽  
Vol 98 (6) ◽  
pp. 1273-1335 ◽  
Author(s):  
Alexander Plotkin ◽  
Elena Gerasimova ◽  
Hans Tore Rapp
Keyword(s):  
North Atlantic ◽  
Related Species ◽  
Molecular Data ◽  
Wide Distribution ◽  
Morphological Data ◽  
Nordic Seas ◽  
Norwegian Sea ◽  
The North ◽  
Western Norway ◽  
The North Atlantic

Polymastiidae (Porifera: Demospongiae) of the Nordic and Siberian Seas are revised and compared with the related species of the North Atlantic based on the morphological data from the type and comparative material and the molecular data from fresh samples. Twenty species from six polymastiid genera are recorded. Two species,Polymastia svensenifrom Western Norway andSpinularia njordifrom the Norwegian Sea, are new to science. One species,Polymastia andrica, is new to the Nordic Seas and two species,Polymastiacf.bartlettiandP. penicillus, are new to the Scandinavian Coast. Distribution of the polymastiids in the North Atlantic and Arctic is discussed and the allegedly wide distribution ofSpinularia sarsiiandS. spinulariais questioned.

scholarly journals A 120 000-year record of sea ice in the North Atlantic?

2019 ◽  
Vol 15 (6) ◽  
pp. 2031-2051 ◽  
Author(s):  
Niccolò Maffezzoli ◽  
Paul Vallelonga ◽  
Ross Edwards ◽  
Alfonso Saiz-Lopez ◽  
Clara Turetta ◽  
...  
Keyword(s):  
Sea Ice ◽  
North Atlantic ◽  
Ice Core ◽  
Arctic Sea Ice ◽  
First Year ◽  
Sea Ice Extent ◽  
Nordic Seas ◽  
The North ◽  
Arctic Sea ◽  
The North Atlantic

Abstract. Although it has been demonstrated that the speed and magnitude of the recent Arctic sea ice decline is unprecedented for the past 1450 years, few records are available to provide a paleoclimate context for Arctic sea ice extent. Bromine enrichment in ice cores has been suggested to indicate the extent of newly formed sea ice areas. Despite the similarities among sea ice indicators and ice core bromine enrichment records, uncertainties still exist regarding the quantitative linkages between bromine reactive chemistry and the first-year sea ice surfaces. Here we present a 120 000-year record of bromine enrichment from the RECAP (REnland ice CAP) ice core, coastal east Greenland, and interpret it as a record of first-year sea ice. We compare it to existing sea ice records from marine cores and tentatively reconstruct past sea ice conditions in the North Atlantic as far north as the Fram Strait (50–85∘ N). Our interpretation implies that during the last deglaciation, the transition from multi-year to first-year sea ice started at ∼17.5 ka, synchronously with sea ice reductions observed in the eastern Nordic Seas and with the increase in North Atlantic ocean temperature. First-year sea ice reached its maximum at 12.4–11.8 ka during the Younger Dryas, after which open-water conditions started to dominate, consistent with sea ice records from the eastern Nordic Seas and the North Icelandic shelf. Our results show that over the last 120 000 years, multi-year sea ice extent was greatest during Marine Isotope Stage (MIS) 2 and possibly during MIS 4, with more extended first-year sea ice during MIS 3 and MIS 5. Sea ice extent during the Holocene (MIS 1) has been less than at any time in the last 120 000 years.

Sign in / Sign up

Export Citation Format

Share Document