The influence of ice sheets on temperature during the past 38 million years inferred from a one-dimensional ice sheet–climate model
Since the inception of the Antarctic ice sheet at the Eocene–Oligocene transition (∼ 34 Myr ago), land ice has played a crucial role in Earth's climate. Through feedbacks in the climate system, land ice variability modifies atmospheric temperature changes induced by orbital, topographical,...
| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
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Copernicus Publications
2017-09-01
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| Series: | Climate of the Past |
| Online Access: | https://www.clim-past.net/13/1243/2017/cp-13-1243-2017.pdf |
| _version_ | 1828418902121512960 |
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| author | L. B. Stap L. B. Stap R. S. W. van de Wal B. de Boer R. Bintanja L. J. Lourens |
| author_facet | L. B. Stap L. B. Stap R. S. W. van de Wal B. de Boer R. Bintanja L. J. Lourens |
| author_sort | L. B. Stap |
| collection | DOAJ |
| description | Since the inception of the Antarctic ice sheet at the
Eocene–Oligocene transition (∼ 34 Myr ago), land ice has
played a crucial role in Earth's climate. Through feedbacks in the
climate system, land ice variability modifies atmospheric
temperature changes induced by orbital, topographical, and greenhouse
gas variations. Quantification of these feedbacks on long timescales has hitherto scarcely been undertaken. In this study, we use
a zonally averaged energy balance climate model bidirectionally
coupled to a one-dimensional ice sheet model, capturing the
ice–albedo and surface–height–temperature feedbacks. Potentially
important transient changes in topographic boundary conditions by
tectonics and erosion are not taken into account but are briefly
discussed. The relative simplicity of the coupled model allows us
to perform integrations over the past 38 Myr in a fully transient
fashion using a benthic oxygen isotope record as forcing to
inversely simulate CO<sub>2</sub>. Firstly, we find that the results
of the simulations over the past 5 Myr are dependent on
whether the model run is started at 5 or 38 Myr ago. This
is because the relation between CO<sub>2</sub> and temperature is
subject to hysteresis. When the climate cools from very high
CO<sub>2</sub> levels, as in the longer transient 38 Myr run,
temperatures in the lower CO<sub>2</sub> range of the past
5 Myr are higher than when the climate is initialised at low
temperatures. Consequently, the modelled CO<sub>2</sub>
concentrations depend on the initial state. Taking the realistic
warm initialisation into account, we come to a best estimate of
CO<sub>2</sub>, temperature, ice-volume-equivalent sea level, and
benthic <i>δ</i><sup>18</sup>O over the past 38 Myr. Secondly,
we study the influence of ice sheets on the evolution of global
temperature and polar amplification by comparing runs with ice
sheet–climate interaction switched on and off. By passing only
albedo or surface height changes to the climate model, we can
distinguish the separate effects of the ice–albedo and
surface–height–temperature feedbacks. We find that ice volume
variability has a strong enhancing effect on atmospheric temperature
changes, particularly in the regions where the ice sheets are
located. As a result, polar amplification in the Northern
Hemisphere decreases towards warmer climates as there is little land
ice left to melt. Conversely, decay of the Antarctic ice sheet
increases polar amplification in the Southern Hemisphere in the
high-CO<sub>2</sub> regime. Our results also show that in cooler
climates than the pre-industrial, the ice–albedo feedback
predominates the surface–height–temperature feedback, while in
warmer climates they are more equal in strength. |
| first_indexed | 2024-12-10T14:44:10Z |
| format | Article |
| id | doaj.art-f717340895dc4c9d9ce236d3ab26c7ad |
| institution | Directory Open Access Journal |
| issn | 1814-9324 1814-9332 |
| language | English |
| last_indexed | 2024-12-10T14:44:10Z |
| publishDate | 2017-09-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Climate of the Past |
| spelling | doaj.art-f717340895dc4c9d9ce236d3ab26c7ad2022-12-22T01:44:36ZengCopernicus PublicationsClimate of the Past1814-93241814-93322017-09-01131243125710.5194/cp-13-1243-2017The influence of ice sheets on temperature during the past 38 million years inferred from a one-dimensional ice sheet–climate modelL. B. Stap0L. B. Stap1R. S. W. van de Wal2B. de Boer3R. Bintanja4L. J. Lourens5Institute for Marine and Atmospheric Research Utrecht (IMAU), Utrecht University, Princetonplein 5, 3584 CC Utrecht, the Netherlandsnow at: Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI), Bussestrasse 24, 27570 Bremerhaven, GermanyInstitute for Marine and Atmospheric Research Utrecht (IMAU), Utrecht University, Princetonplein 5, 3584 CC Utrecht, the NetherlandsInstitute for Marine and Atmospheric Research Utrecht (IMAU), Utrecht University, Princetonplein 5, 3584 CC Utrecht, the NetherlandsRoyal Netherlands Meteorological Institute (KNMI), Utrechtseweg 297, 3731 GA De Bilt, the NetherlandsDepartment of Earth Sciences, Faculty of Geosciences, Utrecht University, Heidelberglaan 2, 3584 CS Utrecht, the NetherlandsSince the inception of the Antarctic ice sheet at the Eocene–Oligocene transition (∼ 34 Myr ago), land ice has played a crucial role in Earth's climate. Through feedbacks in the climate system, land ice variability modifies atmospheric temperature changes induced by orbital, topographical, and greenhouse gas variations. Quantification of these feedbacks on long timescales has hitherto scarcely been undertaken. In this study, we use a zonally averaged energy balance climate model bidirectionally coupled to a one-dimensional ice sheet model, capturing the ice–albedo and surface–height–temperature feedbacks. Potentially important transient changes in topographic boundary conditions by tectonics and erosion are not taken into account but are briefly discussed. The relative simplicity of the coupled model allows us to perform integrations over the past 38 Myr in a fully transient fashion using a benthic oxygen isotope record as forcing to inversely simulate CO<sub>2</sub>. Firstly, we find that the results of the simulations over the past 5 Myr are dependent on whether the model run is started at 5 or 38 Myr ago. This is because the relation between CO<sub>2</sub> and temperature is subject to hysteresis. When the climate cools from very high CO<sub>2</sub> levels, as in the longer transient 38 Myr run, temperatures in the lower CO<sub>2</sub> range of the past 5 Myr are higher than when the climate is initialised at low temperatures. Consequently, the modelled CO<sub>2</sub> concentrations depend on the initial state. Taking the realistic warm initialisation into account, we come to a best estimate of CO<sub>2</sub>, temperature, ice-volume-equivalent sea level, and benthic <i>δ</i><sup>18</sup>O over the past 38 Myr. Secondly, we study the influence of ice sheets on the evolution of global temperature and polar amplification by comparing runs with ice sheet–climate interaction switched on and off. By passing only albedo or surface height changes to the climate model, we can distinguish the separate effects of the ice–albedo and surface–height–temperature feedbacks. We find that ice volume variability has a strong enhancing effect on atmospheric temperature changes, particularly in the regions where the ice sheets are located. As a result, polar amplification in the Northern Hemisphere decreases towards warmer climates as there is little land ice left to melt. Conversely, decay of the Antarctic ice sheet increases polar amplification in the Southern Hemisphere in the high-CO<sub>2</sub> regime. Our results also show that in cooler climates than the pre-industrial, the ice–albedo feedback predominates the surface–height–temperature feedback, while in warmer climates they are more equal in strength.https://www.clim-past.net/13/1243/2017/cp-13-1243-2017.pdf |
| spellingShingle | L. B. Stap L. B. Stap R. S. W. van de Wal B. de Boer R. Bintanja L. J. Lourens The influence of ice sheets on temperature during the past 38 million years inferred from a one-dimensional ice sheet–climate model Climate of the Past |
| title | The influence of ice sheets on temperature during the past 38 million years inferred from a one-dimensional ice sheet–climate model |
| title_full | The influence of ice sheets on temperature during the past 38 million years inferred from a one-dimensional ice sheet–climate model |
| title_fullStr | The influence of ice sheets on temperature during the past 38 million years inferred from a one-dimensional ice sheet–climate model |
| title_full_unstemmed | The influence of ice sheets on temperature during the past 38 million years inferred from a one-dimensional ice sheet–climate model |
| title_short | The influence of ice sheets on temperature during the past 38 million years inferred from a one-dimensional ice sheet–climate model |
| title_sort | influence of ice sheets on temperature during the past 38 million years inferred from a one dimensional ice sheet climate model |
| url | https://www.clim-past.net/13/1243/2017/cp-13-1243-2017.pdf |
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