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

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.

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Does a difference in ice sheets between Marine Isotope Stages 3 and 5a affect the duration of stadials? Implications from hosing experiments

Climate of the Past ◽

10.5194/cp-17-1919-2021 ◽

2021 ◽

Vol 17 (5) ◽

pp. 1919-1936

Author(s):

Sam Sherriff-Tadano ◽

Ayako Abe-Ouchi ◽

Akira Oka ◽

Takahito Mitsui ◽

Fuyuki Saito

Keyword(s):

Sea Ice ◽

Boundary Conditions ◽

Recovery Time ◽

Ice Sheets ◽

Ice Sheet ◽

Meridional Overturning Circulation ◽

Glacial Ice ◽

Formation Region ◽

Background Climate ◽

The Impact

Abstract. Glacial periods undergo frequent climate shifts between warm interstadials and cold stadials on a millennial timescale. Recent studies show that the duration of these climate modes varies with the background climate; a colder background climate and lower CO2 generally result in a shorter interstadial and a longer stadial through its impact on the Atlantic Meridional Overturning Circulation (AMOC). However, the duration of stadials is shorter during Marine Isotope Stage 3 (MIS3) than during MIS5, despite the colder climate in MIS3, suggesting potential control from other climate factors on the duration of stadials. In this study, we investigate the role of glacial ice sheets. For this purpose, freshwater hosing experiments are conducted with an atmosphere–ocean general circulation model under MIS5a and MIS3 boundary conditions, as well as MIS3 boundary conditions with MIS5a ice sheets. The impact of ice sheet differences on the duration of the stadials is evaluated by comparing recovery times of the AMOC after the freshwater forcing is stopped. These experiments show a slightly shorter recovery time of the AMOC during MIS3 compared with MIS5a, which is consistent with ice core data. We find that larger glacial ice sheets in MIS3 shorten the recovery time. Sensitivity experiments show that stronger surface winds over the North Atlantic shorten the recovery time by increasing the surface salinity and decreasing the sea ice amount in the deepwater formation region, which sets favorable conditions for oceanic convection. In contrast, we also find that surface cooling by larger ice sheets tends 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 during MIS3 compared with MIS5a could have contributed to the shortening of stadials in MIS3, despite the climate being colder than that of MIS5a, because surface wind plays a larger role.

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Impact of mid-glacial ice sheets on the recovery time of the AMOC: Implications on the frequent DO cycles during the mid-glacial period

10.5194/egusphere-egu2020-7844 ◽

2020 ◽

Author(s):

Sam Sherriff-Tadano ◽

Ayako Abe-Ouchi

Keyword(s):

Recovery Time ◽

General Circulation ◽

Surface Wind ◽

Ice Sheets ◽

Ice Sheet ◽

Ice Cores ◽

Meridional Overturning Circulation ◽

Glacial Period ◽

Glacial Ice ◽

The Impact

Paleo reconstructions such as ice cores have revealed that the glacial period experienced frequent climate shifts between warm interstadials and cold stadials. The duration of these climate modes varied during glacial periods, and that both the interstadials and stadials were shorter during mid-glacial compared with early glacial period. Recent studies showed that the duration of the interstdials was controlled by the Antarctic temperature through its impact on the Atlantic Meridional Overturning Circulation (AMOC). However, similar relation was not found for the stadials, suggesting that other climate factors (e.g., differences in ice sheet size, greenhouse gases and insolation) might have played a role. In this study, we investigate the role of glacial ice sheets on the duration of stadials. For this purpose, freshwater hosing experiments are conducted with an atmosphere-ocean general circulation model MIROC4m under early-glacial and mid-glacial conditions. Then, a sensitivity experiment is conducted modifying only the configuration of the ice sheets.&#160; The impact of mid-glacial ice sheets on the duration of the stadials is evaluated by comparing the recovery time of the AMOC after the cessation of the freshwater forcing. We find that the expansion of glacial ice sheets during mid-glacial shortens the recovery time of the AMOC. Partially coupled experiments, which switch the surface winds between the two experiments, show that the differences in the surface wind cause the shorter recovery time under mid-glacial ice sheet. The wind shortens the recovery time by increasing the surface salinity and decreasing the sea ice at the deepwater formation region. Thus the results suggest that differences in the surface wind between mid-glacial and early glacial ice sheets play an important role in causing shorter stadials during mid-glacial period.

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Impact of mid-glacial ice sheets on deep ocean circulation and global climate: Role of surface cooling on the AMOC

10.5194/cp-2020-75 ◽

2020 ◽

Author(s):

Sam Sherriff-Tadano ◽

Ayako Abe-Ouchi ◽

Akira Oka

Keyword(s):

North Atlantic ◽

General Circulation ◽

Global Climate ◽

Surface Wind ◽

Ice Sheets ◽

Ice Sheet ◽

Meridional Overturning Circulation ◽

Strengthening Effect ◽

Surface Cooling ◽

Glacial Ice

Abstract. This study explores the effect of southward expansion of mid-glacial ice sheets on the global climate and the Atlantic meridional overturning circulation (AMOC), as well as the processes by which the ice sheets modify the AMOC. For this purpose, simulations of Marine Isotope Stage (MIS) 3 and 5a are performed with an atmosphere-ocean general circulation model. In the MIS3 and MIS5a simulations, the global average temperature decreases by 5.0 °C and 2.2 °C, respectively, compared with the preindustrial climate simulation. The AMOC weakens by 3 % in MIS3, whereas it is enhanced by 16 % in MIS5a, both of which are consistent with a reconstruction. Sensitivity experiments extracting the effect of the expansion of glacial ice sheets from MIS5a to MIS3 show a global cooling of 1.1 °C, contributing to about 40 % of the total surface cooling from MIS5a to MIS3. These experiments also demonstrate that the ice sheet expansion leads to a surface cooling of 2 °C over the Southern Ocean as a result of colder North Atlantic deep water. We find that the southward expansion of the mid-glacial ice sheet exerts a small impact on the AMOC. Partially coupled experiments reveal that the global surface cooling by the glacial ice sheet tends to reduce the AMOC by increasing the sea ice at both poles, and hence compensates for the strengthening effect of the enhanced surface wind over the North Atlantic. Our results show that the total effect of glacial ice sheets on the AMOC is determined by the two competing effects, surface wind and surface cooling. The relative strength of surface wind and surface cooling depends on the ice sheet configuration, and the strength of the surface cooling can be comparable to that of surface wind when changes in the extent of ice sheet are prominent.

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Impact of mid-glacial ice sheets on deep ocean circulation and global climate

10.5194/egusphere-egu21-13538 ◽

2021 ◽

Author(s):

Sam Sherriff-Tadano ◽

Ayako Abe-Ouchi ◽

Akira Oka

Keyword(s):

North Atlantic ◽

Global Climate ◽

Surface Wind ◽

Ice Sheets ◽

Ice Sheet ◽

Meridional Overturning Circulation ◽

Strengthening Effect ◽

Surface Cooling ◽

Glacial Ice ◽

Cooling Effects

This study explores the effect of southward expansion of Northern Hemisphere (American) mid-glacial ice sheets on the global climate and the Atlantic Meridional Overturning Circulation (AMOC), as well as the processes by which the ice sheets modify the AMOC. For this purpose, simulations of Marine Isotope Stage (MIS) 3 (36ka) and 5a (80ka) are performed with an atmosphere-ocean general circulation model. In the MIS3 and MIS5a simulations, the global average temperature decreases by 5.0 &#176;C and 2.2 &#176;C, respectively, compared with the preindustrial climate simulation. The AMOC weakens by 3% in MIS3, whereas it strengthens by 16% in MIS5a, both of which are consistent with an estimate based on 231Pa/230Th. Sensitivity experiments extracting the effect of the southward expansion of glacial ice sheets from MIS5a to MIS3 show a global cooling of 1.1 &#176;C, contributing to about 40% of the total surface cooling from MIS5a to MIS3. These experiments also demonstrate that the ice sheet expansion leads to a surface cooling of 2 &#176;C over the Southern Ocean as a result of colder North Atlantic deep water. We find that the southward expansion of the mid-glacial ice sheet exerts a small impact on the AMOC. Partially coupled experiments reveal that the global surface cooling by the glacial ice sheet tends to reduce the AMOC by increasing the sea ice at both poles, and hence compensates for the strengthening effect of the enhanced surface wind over the North Atlantic. Our results show that the total effect of glacial ice sheets on the AMOC is determined by the two competing effects, surface wind and surface cooling. The relative strength of surface wind and surface cooling effects depends on the ice sheet configuration, and the strength of the surface cooling can be comparable to that of surface wind when changes in the extent of ice sheet are prominent.

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Impact of mid-glacial ice sheets on deep ocean circulation and global climate

Climate of the Past ◽

10.5194/cp-17-95-2021 ◽

2021 ◽

Vol 17 (1) ◽

pp. 95-110

Author(s):

Sam Sherriff-Tadano ◽

Ayako Abe-Ouchi ◽

Akira Oka

Keyword(s):

North Atlantic ◽

Global Climate ◽

Surface Wind ◽

Ice Sheets ◽

Ice Sheet ◽

Meridional Overturning Circulation ◽

Strengthening Effect ◽

Surface Cooling ◽

Glacial Ice ◽

Cooling Effects

Abstract. This study explores the effect of southward expansion of Northern Hemisphere (American) mid-glacial ice sheets on the global climate and the Atlantic Meridional Overturning Circulation (AMOC) as well as the processes by which the ice sheets modify the AMOC. For this purpose, simulations of Marine Isotope Stage (MIS) 3 (36 ka) and 5a (80 ka) are performed with an atmosphere–ocean general circulation model. In the MIS3 and MIS5a simulations, the global average temperature decreases by 5.0 and 2.2 ∘C, respectively, compared with the preindustrial climate simulation. The AMOC weakens by 3 % in MIS3, whereas it strengthens by 16 % in MIS5a, both of which are consistent with an estimate based on 231Pa ∕ 230Th. Sensitivity experiments extracting the effect of the southward expansion of glacial ice sheets from MIS5a to MIS3 show a global cooling of 1.1 ∘C, contributing to about 40 % of the total surface cooling from MIS5a to MIS3. These experiments also demonstrate that the ice sheet expansion leads to a surface cooling of 2 ∘C over the Southern Ocean as a result of colder North Atlantic Deep Water. We find that the southward expansion of the mid-glacial ice sheet exerts a small impact on the AMOC. Partially coupled experiments reveal that the global surface cooling by the glacial ice sheet tends to reduce the AMOC by increasing the sea ice at both poles and, hence, compensates for the strengthening effect of the enhanced surface wind over the North Atlantic. Our results show that the total effect of glacial ice sheets on the AMOC is determined by two competing effects: surface wind and surface cooling. The relative strength of surface wind and surface cooling effects depends on the ice sheet configuration, and the strength of the surface cooling can be comparable to that of surface wind when changes in the extent of ice sheet are prominent.

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Last Interglacial climate and sea-level evolution from a coupled ice sheet–climate model

Climate of the Past ◽

10.5194/cp-12-2195-2016 ◽

2016 ◽

Vol 12 (12) ◽

pp. 2195-2213 ◽

Cited By ~ 22

Author(s):

Heiko Goelzer ◽

Philippe Huybrechts ◽

Marie-France Loutre ◽

Thierry Fichefet

Keyword(s):

Surface Temperature ◽

Sea Level ◽

Ice Sheets ◽

Ice Sheet ◽

Greenland Ice Sheet ◽

Last Interglacial ◽

A Minor ◽

The Antarctic ◽

The Impact ◽

And Sea Level

Abstract. As the most recent warm period in Earth's history with a sea-level stand higher than present, the Last Interglacial (LIG, ∼  130 to 115 kyr BP) is often considered a prime example to study the impact of a warmer climate on the two polar ice sheets remaining today. Here we simulate the Last Interglacial climate, ice sheet, and sea-level evolution with the Earth system model of intermediate complexity LOVECLIM v.1.3, which includes dynamic and fully coupled components representing the atmosphere, the ocean and sea ice, the terrestrial biosphere, and the Greenland and Antarctic ice sheets. In this setup, sea-level evolution and climate–ice sheet interactions are modelled in a consistent framework.Surface mass balance change governed by changes in surface meltwater runoff is the dominant forcing for the Greenland ice sheet, which shows a peak sea-level contribution of 1.4 m at 123 kyr BP in the reference experiment. Our results indicate that ice sheet–climate feedbacks play an important role to amplify climate and sea-level changes in the Northern Hemisphere. The sensitivity of the Greenland ice sheet to surface temperature changes considerably increases when interactive albedo changes are considered. Southern Hemisphere polar and sub-polar ocean warming is limited throughout the Last Interglacial, and surface and sub-shelf melting exerts only a minor control on the Antarctic sea-level contribution with a peak of 4.4 m at 125 kyr BP. Retreat of the Antarctic ice sheet at the onset of the LIG is mainly forced by rising sea level and to a lesser extent by reduced ice shelf viscosity as the surface temperature increases. Global sea level shows a peak of 5.3 m at 124.5 kyr BP, which includes a minor contribution of 0.35 m from oceanic thermal expansion. Neither the individual contributions nor the total modelled sea-level stand show fast multi-millennial timescale variations as indicated by some reconstructions.

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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

Climate of the Past ◽

10.5194/cp-9-1629-2013 ◽

2013 ◽

Vol 9 (4) ◽

pp. 1629-1643 ◽

Cited By ~ 23

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.

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Reduced Stability of the Atlantic Meridional Overturning Circulation due to Wind Stress Feedback during Glacial Times

Journal of Climate ◽

10.1175/2008jcli2291.1 ◽

2008 ◽

Vol 21 (23) ◽

pp. 6260-6282 ◽

Cited By ~ 14

Author(s):

Olivier Arzel ◽

Matthew H. England ◽

Willem P. Sijp

Keyword(s):

Sea Ice ◽

Wind Stress ◽

Surface Wind ◽

Meridional Overturning Circulation ◽

Nonlinear Dependence ◽

Upper Ocean ◽

Overturning Circulation ◽

Climate Conditions ◽

Meridional Overturning ◽

The Impact

Abstract A previous study by Mikolajewicz suggested that the wind stress feedback stabilizes the Atlantic thermohaline circulation. This result was obtained under modern climate conditions, for which the presence of the massive continental ice sheets characteristic of glacial times is missing. Here a coupled ocean–atmosphere–sea ice model of intermediate complexity, set up in an idealized spherical sector geometry of the Atlantic basin, is used to show that, under glacial climate conditions, wind stress feedback actually reduces the stability of the meridional overturning circulation (MOC). The analysis reveals that the influence of the wind stress feedback on the glacial MOC response to an external source of freshwater applied at high northern latitudes is controlled by the following two distinct processes: 1) the interactions between the wind field and the sea ice export in the Northern Hemisphere (NH), and 2) the northward Ekman transport in the tropics and upward Ekman pumping in the core of the NH subpolar gyre. The former dominates the response of the coupled system; it delays the recovery of the MOC, and in some cases even stabilizes collapsed MOC states achieved during the hosing period. The latter plays a minor role and mitigates the impact of the former process by reducing the upper-ocean freshening in deep-water formation regions. Hence, the wind stress feedback delays the recovery of the glacial MOC, which is the opposite of what occurs under modern climate conditions. Close to the critical transition threshold beyond which the circulation collapses, the glacial MOC appears to be very sensitive to changes in surface wind stress forcing and exhibits, in the aftermath of the freshwater pulse, a nonlinear dependence upon the wind stress feedback magnitude: a complete and irreversible MOC shutdown occurs only for intermediate wind stress feedback magnitudes. This behavior results from the competitive effects of processes 1 and 2 on the midlatitude upper-ocean salinity during the shutdown phase of the MOC. The mechanisms presented here may be relevant to the large meltwater pulses that punctuated the last glacial period.

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Influence of ablation-related processes in the built-up of simulated Northern Hemisphere ice sheets during the last glacial cycle

The Cryosphere Discussions ◽

10.5194/tcd-6-4897-2012 ◽

2012 ◽

Vol 6 (6) ◽

pp. 4897-4938 ◽

Cited By ~ 1

Author(s):

S. Charbit ◽

C. Dumas ◽

M. Kageyama ◽

D. M. Roche ◽

C. Ritz

Keyword(s):

Northern Hemisphere ◽

Ice Sheets ◽

Ice Sheet ◽

Glacial Cycle ◽

Satisfactory Description ◽

Last Glacial ◽

Transient Simulations ◽

Main Driver ◽

The Impact ◽

The Last Glacial

Abstract. Since the original formulation of the positive-degree-day (PDD) method, different PDD calibrations have been proposed in the literature in response to the increasing number of observations. Although these formulations provide a satisfactory description of the present-day Greenland geometry, they have not all been tested for paleo ice sheets. Using the climate-ice sheet model CLIMBER-GRISLI coupled with different PDD models, we evaluate how the parameterization of the ablation may affect the evolution of Northern Hemisphere ice sheets in the transient simulations of the last glacial cycle. Results from fully coupled simulations are compared to time-slice experiments carried out at different key periods of the last glacial period. We find large differences in the simulated ice sheets according to the chosen PDD model. These differences occur as soon as the onset of glaciation, therefore affecting the subsequent evolution of the ice system. To further investigate how the PDD method controls this evolution, special attention is given to the role of each PDD parameter. We show that glacial inception is critically dependent on the representation of the impact of the temperature variability from the daily to the inter-annual time scale, whose effect is modulated by the refreezing scheme. Finally, an additional set of sensitivity experiments has been carried out to assess the relative importance of melt processes with respect to initial ice sheet configuration in the construction and the evolution of past Northern Hemisphere ice sheets. Our analysis reveals that the impacts of the initial ice sheet condition may range from quite negligible to explaining about half of the LGM ice volume depending on the representation of stochastic temperature variations which remain the main driver of the evolution of the ice system.

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Elastic properties of floating sea ice from air-coupled flexural waves

10.5194/tc-2021-71 ◽

2021 ◽

Author(s):

Rowan Romeyn ◽

Alfred Hanssen ◽

Bent Ole Ruud ◽

Tor Arne Johansen

Keyword(s):

Sea Ice ◽

Elastic Properties ◽

Ice Sheets ◽

Ice Sheet ◽

Flexural Wave ◽

Ice Thickness ◽

Linear Filter ◽

Flexural Stiffness ◽

Flexural Waves ◽

Impulsive Source

Abstract. Air-coupled flexural waves appear as wave trains of constant frequency that arrive in advance of the direct air-wave from an impulsive source travelling over a floating ice sheet. The frequency of these waves varies with the flexural stiffness of the ice sheet, which is controlled by a combination of thickness and elastic properties. We develop a theoretical framework to understand these waves, utilizing modern numerical and Fourier methods to give a simpler and more accessible description than the pioneering, yet unwieldly analytical efforts of the 1950's. Our favoured dynamical model can be understood in terms of linear filter theory and is closely related to models used to describe the flexural waves produced by moving vehicles on floating plates. We find that air-coupled flexural waves are a robust feature of floating ice-sheets excited by impulsive sources over a large range of thicknesses, and we present a simple closed-form estimator for the ice thickness. Our study is focussed on first-year sea ice of ~20–80 cm thickness in Van Mijenfjorden, Svalbard, that was investigated through active source seismic experiments over four field campaigns in 2013, 2016, 2017 and 2018. The air-coupled flexural frequencies for sea-ice in this thickness range are ~60–240 Hz. While air-coupled flexural waves for thick sea-ice have received little attention, the higher frequencies associated with thin ice on fresh water lakes and rivers are well known to the ice-skating community and have been reported in popular media. Estimation of ice physical properties, following the approach we present, may allow improved surface wave modelling and wavefield subtraction in reflection seismic studies where flexural wave noise is undesirable. On the other hand, air-coupled flexural waves may also permit non-destructive continuous monitoring of ice thickness and flexural stiffness using simple, relatively inexpensive microphones located in the vicinity of the desired measurement location, either above the ice-sheet or along the shoreline. In this case, naturally forming cracks in the ice may be an appropriate impulsive source capable of exciting flexural waves in floating ice sheets in a passive monitoring context.

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