Warm Deep Water Variability During the Last Millennium in the CESM–LME: Pre-Industrial Scenario versus Late 20th Century Changes
Water transformation around Antarctica is recognized to significantly impact the climate. It is where the linkage between the upper and lower limbs of the Meridional Overturning Circulation (MOC) takes place by means of dense water formation, which may be affected by rapid climate change. Simulation...
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MDPI AG
2019-08-01
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| Series: | Geosciences |
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| Online Access: | https://www.mdpi.com/2076-3263/9/8/346 |
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| author | Marcos Tonelli Fernanda Marcello Bruno Ferrero Ilana Wainer |
| author_facet | Marcos Tonelli Fernanda Marcello Bruno Ferrero Ilana Wainer |
| author_sort | Marcos Tonelli |
| collection | DOAJ |
| description | Water transformation around Antarctica is recognized to significantly impact the climate. It is where the linkage between the upper and lower limbs of the Meridional Overturning Circulation (MOC) takes place by means of dense water formation, which may be affected by rapid climate change. Simulation results from the Community Earth System Model Last Millennium Ensemble (CESM−LME) are used to investigate the Weddell Sea Warm Deep Water (WDW) evolution during the Last Millennium (LM). The WDW is the primary heat source for the Weddell Sea (WS) and accounts for 71% of the Weddell Sea Bottom Water (WSBW), which is the regional variety of the Antarctic Bottom Water (AABW)—one of the densest water masses in the ocean bearing directly on the cold deep limb of the MOC. <i>Earth System Models</i> (ESMs) are known to misrepresent the deep layers of the ocean (below 2000 m), hence we aim at the upper component of the deep meridional overturning cell, i.e., the WDW. Salinity and temperature results from the CESM−LME from a transect crossing the WS are evaluated with the Optimum Multiparameter Analysis (OMP) water masses decomposition scheme. It is shown that, after a long−term cooling over the LM, a warming trend takes place at the surface waters in the WS during the 20th century, which is coherent with a global expression. The subsurface layers and. mainly. the WDW domain are subject to the same long−term cooling trend, which is decelerated after 1850 (instead of becoming warmer like the surface waters), probably due interactions with sea ice−insulated ambient waters. The evolution of this anomalous temperature pattern for the WS is clear throughout the three major LM climatic episodes: the Medieval Climate Anomaly (MCA), Little Ice Age (LIA) and late 20th century warming. Along with the continuous decline of WDW core temperatures, heat content in the water mass also decreases by 18.86%. OMP results indicate shoaling and shrinking of the WDW during the LM, with a ~6% decrease in its cross−sectional area. Although the AABW cannot be directly assessed from CESM−LME results, changes in the WDW structure and WS dynamics have the potential to influence the deep/bottom water formation processes and the global MOC. |
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| language | English |
| last_indexed | 2024-12-11T22:25:54Z |
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| spelling | doaj.art-49534f72290d4d73b851ea8d63c1561a2022-12-22T00:48:17ZengMDPI AGGeosciences2076-32632019-08-019834610.3390/geosciences9080346geosciences9080346Warm Deep Water Variability During the Last Millennium in the CESM–LME: Pre-Industrial Scenario versus Late 20th Century ChangesMarcos Tonelli0Fernanda Marcello1Bruno Ferrero2Ilana Wainer3Department of Physical Oceanography, Oceanographic Institute of the University of São Paulo, São Paulo 05508–120, BrazilDepartment of Physical Oceanography, Oceanographic Institute of the University of São Paulo, São Paulo 05508–120, BrazilDepartment of Physical Oceanography, Oceanographic Institute of the University of São Paulo, São Paulo 05508–120, BrazilDepartment of Physical Oceanography, Oceanographic Institute of the University of São Paulo, São Paulo 05508–120, BrazilWater transformation around Antarctica is recognized to significantly impact the climate. It is where the linkage between the upper and lower limbs of the Meridional Overturning Circulation (MOC) takes place by means of dense water formation, which may be affected by rapid climate change. Simulation results from the Community Earth System Model Last Millennium Ensemble (CESM−LME) are used to investigate the Weddell Sea Warm Deep Water (WDW) evolution during the Last Millennium (LM). The WDW is the primary heat source for the Weddell Sea (WS) and accounts for 71% of the Weddell Sea Bottom Water (WSBW), which is the regional variety of the Antarctic Bottom Water (AABW)—one of the densest water masses in the ocean bearing directly on the cold deep limb of the MOC. <i>Earth System Models</i> (ESMs) are known to misrepresent the deep layers of the ocean (below 2000 m), hence we aim at the upper component of the deep meridional overturning cell, i.e., the WDW. Salinity and temperature results from the CESM−LME from a transect crossing the WS are evaluated with the Optimum Multiparameter Analysis (OMP) water masses decomposition scheme. It is shown that, after a long−term cooling over the LM, a warming trend takes place at the surface waters in the WS during the 20th century, which is coherent with a global expression. The subsurface layers and. mainly. the WDW domain are subject to the same long−term cooling trend, which is decelerated after 1850 (instead of becoming warmer like the surface waters), probably due interactions with sea ice−insulated ambient waters. The evolution of this anomalous temperature pattern for the WS is clear throughout the three major LM climatic episodes: the Medieval Climate Anomaly (MCA), Little Ice Age (LIA) and late 20th century warming. Along with the continuous decline of WDW core temperatures, heat content in the water mass also decreases by 18.86%. OMP results indicate shoaling and shrinking of the WDW during the LM, with a ~6% decrease in its cross−sectional area. Although the AABW cannot be directly assessed from CESM−LME results, changes in the WDW structure and WS dynamics have the potential to influence the deep/bottom water formation processes and the global MOC.https://www.mdpi.com/2076-3263/9/8/346Warm Deep WaterWeddell Sealast millenniumlate twentieth century |
| spellingShingle | Marcos Tonelli Fernanda Marcello Bruno Ferrero Ilana Wainer Warm Deep Water Variability During the Last Millennium in the CESM–LME: Pre-Industrial Scenario versus Late 20th Century Changes Geosciences Warm Deep Water Weddell Sea last millennium late twentieth century |
| title | Warm Deep Water Variability During the Last Millennium in the CESM–LME: Pre-Industrial Scenario versus Late 20th Century Changes |
| title_full | Warm Deep Water Variability During the Last Millennium in the CESM–LME: Pre-Industrial Scenario versus Late 20th Century Changes |
| title_fullStr | Warm Deep Water Variability During the Last Millennium in the CESM–LME: Pre-Industrial Scenario versus Late 20th Century Changes |
| title_full_unstemmed | Warm Deep Water Variability During the Last Millennium in the CESM–LME: Pre-Industrial Scenario versus Late 20th Century Changes |
| title_short | Warm Deep Water Variability During the Last Millennium in the CESM–LME: Pre-Industrial Scenario versus Late 20th Century Changes |
| title_sort | warm deep water variability during the last millennium in the cesm lme pre industrial scenario versus late 20th century changes |
| topic | Warm Deep Water Weddell Sea last millennium late twentieth century |
| url | https://www.mdpi.com/2076-3263/9/8/346 |
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