scholarly journals Wind Feedback Mediated by Sea Ice in the Nordic Seas

2020 ◽  
Vol 33 (15) ◽  
pp. 6621-6632
Author(s):  
Tamás Kovács ◽  
Rüdiger Gerdes ◽  
John Marshall
Keyword(s):  
Sea Ice ◽  
Critical Role ◽  
Pressure Gradients ◽  
Surface Cooling ◽  
Wind Anomaly ◽  
Sea Level Pressure ◽  
Nordic Seas ◽  
Induced Changes ◽  
Fully Coupled ◽  
Partial Coupling

AbstractAir–sea interactions play a critical role in the climate system. This study investigates wind-induced changes in the ocean surface temperature and sea ice cover feeding back onto the atmospheric circulation. This interaction was modeled in the Nordic seas, using a partial coupling method to constrain the ocean with prescribed wind forcing in an otherwise fully coupled Earth system model. This enabled the evaluation of not only the direct oceanic, but also the indirect atmospheric response to idealized forcing scenarios of perturbed winds over the Nordic seas. The results show that an anticyclonic wind anomaly forcing leads to significant surface cooling in the Greenland Sea mostly due to anomalous drift of sea ice. During winter, the cooling reduces the net surface heat flux to the atmosphere and increases sea level pressure. The pressure gradients result in anomalous geostrophic southerly winds, which locally are comparable both in direction and in velocity to the prescribed forcing anomalies, suggesting a positive feedback.

scholarly journals The Holocene thermal maximum in the Nordic Seas: the impact of Greenland Ice Sheet melt and other forcings in a coupled atmosphere–sea-ice–ocean model

2013 ◽  
Vol 9 (4) ◽  
pp. 1629-1643 ◽  
Author(s):  
M. Blaschek ◽  
H. Renssen
Keyword(s):  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Early Holocene ◽  
Surface Cooling ◽  
Holocene Climate ◽  
Nordic Seas ◽  
The Holocene ◽  
Holocene Thermal Maximum ◽  
Thermal Maximum ◽  
The Impact

Abstract. The relatively warm early Holocene climate in the Nordic Seas, known as the Holocene thermal maximum (HTM), is often associated with an orbitally forced summer insolation maximum at 10 ka BP. The spatial and temporal response recorded in proxy data in the North Atlantic and the Nordic Seas reveals a complex interaction of mechanisms active in the HTM. Previous studies have investigated the impact of the Laurentide Ice Sheet (LIS), as a remnant from the previous glacial period, altering climate conditions with a continuous supply of melt water to the Labrador Sea and adjacent seas and with a downwind cooling effect from the remnant LIS. In our present work we extend this approach by investigating the impact of the Greenland Ice Sheet (GIS) on the early Holocene climate and the HTM. Reconstructions suggest melt rates of 13 mSv for 9 ka BP, which result in our model in an ocean surface cooling of up to 2 K near Greenland. Reconstructed summer SST gradients agree best with our simulation including GIS melt, confirming that the impact of the early Holocene GIS is crucial for understanding the HTM characteristics in the Nordic Seas area. This implies that modern and near-future GIS melt can be expected to play an active role in the climate system in the centuries to come.

scholarly journals North Atlantic deep water formation and AMOC in CMIP5 models

Ocean Science ◽  
2017 ◽  
Vol 13 (4) ◽  
pp. 609-622 ◽  
Author(s):  
Céline Heuzé
Keyword(s):  
Sea Ice ◽  
Ocean Circulation ◽  
North Atlantic ◽  
Deep Water ◽  
Deep Convection ◽  
The Arctic ◽  
Subpolar Gyre ◽  
Deep Water Formation ◽  
Nordic Seas ◽  
Water Formation

Abstract. Deep water formation in climate models is indicative of their ability to simulate future ocean circulation, carbon and heat uptake, and sea level rise. Present-day temperature, salinity, sea ice concentration and ocean transport in the North Atlantic subpolar gyre and Nordic Seas from 23 CMIP5 (Climate Model Intercomparison Project, phase 5) models are compared with observations to assess the biases, causes and consequences of North Atlantic deep convection in models. The majority of models convect too deep, over too large an area, too often and too far south. Deep convection occurs at the sea ice edge and is most realistic in models with accurate sea ice extent, mostly those using the CICE model. Half of the models convect in response to local cooling or salinification of the surface waters; only a third have a dynamic relationship between freshwater coming from the Arctic and deep convection. The models with the most intense deep convection have the warmest deep waters, due to a redistribution of heat through the water column. For the majority of models, the variability of the Atlantic Meridional Overturning Circulation (AMOC) is explained by the volumes of deep water produced in the subpolar gyre and Nordic Seas up to 2 years before. In turn, models with the strongest AMOC have the largest heat export to the Arctic. Understanding the dynamical drivers of deep convection and AMOC in models is hence key to realistically forecasting Arctic oceanic warming and its consequences for the global ocean circulation, cryosphere and marine life.

scholarly journals How much should we believe correlations between Arctic cyclones and sea ice extent?

2017 ◽  
Author(s):  
Jamie G. L. Rae ◽  
Alexander D. Todd ◽  
Edward W. Blockley ◽  
Jeff K. Ridley
Keyword(s):  
Sea Ice ◽  
Climate Model ◽  
Arctic Sea Ice ◽  
Reanalysis Dataset ◽  
Sea Ice Extent ◽  
Sea Level Pressure ◽  
Temporal Sampling ◽  
Time Period ◽  
Arctic Sea ◽  
Short Time

Abstract. This paper presents an analysis of Arctic summer cyclones in a climate model and in a reanalysis dataset. A cyclone identification and tracking algorithm is run for output from model simulations at two resolutions, and for the reanalysis, using two different tracking variables (mean sea-level pressure and 850 hPa vorticity) for identification of the cyclones. Correlations between characteristics of the cyclones and September Arctic sea ice extent are investigated, and the influence of the tracking variable, the spatial resolution of the model, and spatial and temporal sampling, on the correlations is explored. We conclude that the correlations obtained depend on all of these factors, and that care should be taken when interpreting the results of such analyses, especially when the focus is on one reanalysis, or output from one model, analysed with a single tracking variable for a short time period.

scholarly journals Does a difference in ice sheets between Marine Isotope Stages 3 and 5a affect the duration of stadials?

2021 ◽  
Author(s):  
Sam Sherriff-Tadano ◽  
Ayako Abe-Ouchi ◽  
Akira Oka ◽  
Takahito Mitsui ◽  
Fuyuki Saito
Keyword(s):  
Sea Ice ◽  
Recovery Time ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Meridional Overturning Circulation ◽  
Surface Cooling ◽  
Glacial Ice ◽  
Formation Region ◽  
Background Climate ◽  
The Impact

Abstract. Glacial periods undergo frequent climate shifts between warm interstadials and cold stadials on a millennial time-scale. Recent studies have shown that the duration of these climate modes varies with the background climate; a colder background climate and lower CO2 generally results in a shorter interstadial and a longer stadial through its impact on the Atlantic Meridional Overturning Circulation (AMOC). However, the duration of stadials was shorter during the Marine Isotope Stage 3 (MIS3) compared with MIS5, despite the colder climate in MIS3, suggesting potential control from other climate factors on the duration of stadials. In this study, we investigated the role of glacial ice sheets. For this purpose, freshwater hosing experiments were conducted with an atmosphere–ocean general circulation model under MIS5a, MIS3 and MIS3 with MIS5a ice sheet conditions. The impact of ice sheet differences on the duration of the stadials was evaluated by comparing recovery times of the AMOC after freshwater forcing was reduced. Hosing experiments showed a slightly shorter recovery time of the AMOC in MIS3 compared with MIS5a, which was consistent with ice core data. We found that larger glacial ice sheets in MIS3 shortened the recovery time. Sensitivity experiments showed that stronger surface winds over the North Atlantic shortened the recovery time by increasing the surface salinity and decreasing the sea ice amount in the deepwater formation region, which set favourable conditions for oceanic convection. In contrast, we also found that surface cooling by larger ice sheets tended to increase the recovery time of the AMOC by increasing the sea ice thickness over the deepwater formation region. Thus, this study suggests that the larger ice sheet in MIS3 compared with MIS5a could have contributed to the shortening of stadials in MIS3, despite the climate being colder than that of MIS5a, when the effect of surface wind played a larger role.

scholarly journals The Response of the Nordic Seas to Wintertime Sea-ice Retreat

2021 ◽  
pp. 1-40
Author(s):  
Yue Wu ◽  
David P. Stevens ◽  
Ian A. Renfrew ◽  
Xiaoming Zhai
Keyword(s):  
Global Warming ◽  
Sea Ice ◽  
Climate Model ◽  
Sea Temperature ◽  
Nordic Seas ◽  
Ocean Response ◽  
Marginal Ice Zone ◽  
Ice Retreat ◽  
Ice Edge ◽  
Sea Ice Retreat

AbstractThe ocean response to wintertime sea-ice retreat is investigated in the coupled climate model HiGEM. We focus on the marginal ice zone and adjacent waters of the Nordic Seas, where the air-sea temperature difference can be large during periods of off-ice winds promoting high heat flux events. Both control and transient climate model ensembles are examined, which allows us to isolate the ocean response due to sea-ice retreat from the response due to climate change. As the wintertime sea-ice edge retreats towards the Greenland coastline, it exposes waters that were previously covered by ice which enhances turbulent heat loss and mechanical mixing, leading to a greater loss of buoyancy and deeper vertical mixing in this location. However, under global warming, the buoyancy loss is inhibited as the atmosphere warms more rapidly than the ocean which reduces the air-sea temperature difference. This occurs most prominently further away from the retreating ice edge, over the Greenland Sea gyre. Over the gyre the upper ocean also warms significantly, resulting in a more stratified water column and, as a consequence, a reduction in the depth of convective mixing. In contrast, closer to the coast the effect of global warming is overshadowed by the effect of the sea-ice retreat, leading to significant changes in ocean temperature and salinity in the vicinity of the marginal ice zone.

scholarly journals PARASO, a circum-Antarctic fully-coupled ice-sheet - ocean - sea-ice - atmosphere - land model involving f.ETISh1.7, NEMO3.6, LIM3.6, COSMO5.0 and CLM4.5

2021 ◽  
Author(s):  
Charles Pelletier ◽  
Thierry Fichefet ◽  
Hugues Goosse ◽  
Konstanze Haubner ◽  
Samuel Helsen ◽  
...  
Keyword(s):  
Sea Ice ◽  
Climate Model ◽  
Regional Climate ◽  
Ice Sheet ◽  
Horizontal Resolution ◽  
Fine Tuning ◽  
Polar Regions ◽  
Surface Mass ◽  
The Impact ◽  
Fully Coupled

Abstract. We introduce PARASO, a novel five-component fully-coupled regional climate model over an Antarctic circumpolar domain covering the full Southern Ocean. The state-of-the-art models used are f.ETISh1.7 (ice sheet), NEMO3.6 (ocean), LIM3.6 (sea ice), COSMO5.0 (atmosphere) and CLM4.5 (land), which are here run at an horizontal resolution close to 1/4°. One key-feature of this tool resides in a novel two-way coupling interface for representing ocean – ice-sheet interactions, through explicitly resolved ice-shelf cavities. The impact of atmospheric processes on the Antarctic ice sheet is also conveyed through computed COSMO-CLM – f.ETISh surface mass exchanges. In this technical paper, we briefly introduce each model's configuration and document the developments that were carried out in order to establish PARASO. The new offline-based NEMO – f.ETISh coupling interface is thoroughly described. Our developments also include a new surface tiling approach to combine open-ocean and sea-ice covered cells within COSMO, which was required to make this model relevant in the context of coupled simulations in polar regions. We present results from a 2000–2001 coupled two-year experiment. PARASO is numerically stable and fully operational. The 2-year simulation conducted without fine tuning of the model reproduced the main expected features, although remaining systematic biases provide perspectives for further adjustment and development.

Influence of Nordic Seas dynamics on the Atlantic Water propagation and its impacts on sea ice concentration.

2021 ◽  
Author(s):  
Sourav Chatterjee ◽  
Roshin P Raj ◽  
Laurent Bertino ◽  
Nuncio Murukesh
Keyword(s):  
Sea Ice ◽  
Deep Water ◽  
Atlantic Water ◽  
The Arctic ◽  
Deep Water Formation ◽  
Sea Ice Concentration ◽  
Nordic Seas ◽  
Ice Concentration ◽  
Water Formation

<p>Enhanced intrusion of warm and saline Atlantic Water (AW) to the Arctic Ocean (AO) in recent years has drawn wide interest of the scientific community owing to its potential role in ‘Arctic Amplification’. Not only the AW has warmed over the last few decades , but its transfer efficiency have also undergone significant modifications due to changes in atmosphere and ocean dynamics at regional to large scales. The Nordic Seas (NS), in this regard, play a vital role as the major exchange of polar and sub-polar waters takes place in this region. Further, the AW and its significant modification on its way to AO via the Nordic Seas has large scale implications on e.g., deep water formation, air-sea heat fluxes. Previous studies have suggested that a change in the sub-polar gyre dynamics in the North Atlantic controls the AW anomalies that enter the NS and eventually end up in the AO. However, the role of NS dynamics in resulting in the modifications of these AW anomalies are not well studied. Here in this study, we show that the Nordic Seas are not only a passive conduit of AW anomalies but the ocean circulations in the Nordic Seas, particularly the Greenland Sea Gyre (GSG) circulation can significantly change the AW characteristics between the entry and exit point of AW in the NS. Further, it is shown that the change in GSG circulation can modify the AW heat distribution in the Nordic Seas and can potentially influence the sea ice concentration therein. Projected enhanced atmospheric forcing in the NS in a warming Arctic scenario and the warming trend of the AW can amplify the role of NS circulation in AW propagation and its impact on sea ice, freshwater budget and deep water formation.</p>

Intracellular Ca2+ signalling in secretory cells.

1997 ◽  
Vol 200 (2) ◽  
pp. 303-314
Author(s):  
T J Shuttleworth
Keyword(s):  
Arachidonic Acid ◽  
Calcium Ion ◽  
Critical Role ◽  
Secretory Activity ◽  
Secretory Cells ◽  
Free Calcium ◽  
Cytosolic Free Calcium ◽  
Maximal Stimulation ◽  
Induced Changes ◽  
Extracellular Environment

The secretion of ions and fluid plays a critical role in a variety of physiological activities that are vital to homeostatic mechanisms in animals. Control of such secretory activity is achieved by a range of neurotransmitters and hormones many of which act intracellularly by generating the second messenger inositol 1,4,5-trisphosphate (InsP3) and increasing cytosolic free calcium ion concentrations ([Ca2+]i). These increases are achieved by a combination of the InsP3-induced release of Ca2+ from specific intracellular stores and the activation of Ca2+ entry from the extracellular environment. The [Ca2+]i signal represents a balance between the adequate activation of components of the secretory mechanism and the avoidance of [Ca2+]i levels that are toxic to the cell. Resting [Ca2+]i is maintained low by the action of Ca2+ pumps on the intracellular stores and plasma membrane, with the result that gradients for Ca2+ movement into the cytosol from either of these two sources are very large and there is considerable potential for achieving rapid increases in [Ca2+]i. Consequently, for successful Ca2+ signalling, it is imperative that these two mechanisms of raising [Ca2+]i (i.e. Ca2+ release and Ca2+ entry) are closely integrated. Current models emphasize the activation of Ca2+ entry as a downstream result of the emptying of the intracellular stores ("capacitative' model). Whilst this may be true for situations of maximal stimulation, recent experiments on the oscillatory [Ca2+]i responses typical of more physiological levels of stimulation indicate a previously unsuspected, independent activation of Ca2+ entry involving arachidonic acid. This arachidonic-acid-activated entry plays a key role, along with InsP3, in inducing the repetitive release of Ca2+ from the stores to produce the [Ca2+]i oscillations. In this way, the two components responsible for the elevation of [Ca2+]i are intimately related and their dual effects closely coordinated, resulting in the finely tuned control of agonist-induced changes in [Ca2+]i.

scholarly journals Sea ice volume variability and water temperature in the Greenland Sea

2020 ◽  
Vol 14 (2) ◽  
pp. 477-495 ◽  
Author(s):  
Valeria Selyuzhenok ◽  
Igor Bashmachnikov ◽  
Robert Ricker ◽  
Anna Vesman ◽  
Leonid Bobylev
Keyword(s):  
Sea Ice ◽  
North Atlantic ◽  
Heat Content ◽  
The Arctic ◽  
Fram Strait ◽  
Greenland Sea ◽  
Nordic Seas ◽  
Ice Volume ◽  
Long Term Variations

Abstract. This study explores a link between the long-term variations in the integral sea ice volume (SIV) in the Greenland Sea and oceanic processes. Using the Pan-Arctic Ice Ocean Modeling and Assimilation System (PIOMAS, 1979–2016), we show that the increasing sea ice volume flux through Fram Strait goes in parallel with a decrease in SIV in the Greenland Sea. The overall SIV loss in the Greenland Sea is 113 km3 per decade, while the total SIV import through Fram Strait increases by 115 km3 per decade. An analysis of the ocean temperature and the mixed-layer depth (MLD) over the climatic mean area of the winter marginal sea ice zone (MIZ) revealed a doubling of the amount of the upper-ocean heat content available for the sea ice melt from 1993 to 2016. This increase alone can explain the SIV loss in the Greenland Sea over the 24-year study period, even when accounting for the increasing SIV flux from the Arctic. The increase in the oceanic heat content is found to be linked to an increase in temperature of the Atlantic Water along the main currents of the Nordic Seas, following an increase in the oceanic heat flux from the subtropical North Atlantic. We argue that the predominantly positive winter North Atlantic Oscillation (NAO) index during the 4 most recent decades, together with an intensification of the deep convection in the Greenland Sea, is responsible for the intensification of the cyclonic circulation pattern in the Nordic Seas, which results in the observed long-term variations in the SIV.

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