Amplified North Atlantic warming in the late Pliocene by changes in Arctic gateways

Abstract

Under previous reconstructions of late Pliocene boundary conditions, climate models have failed to reproduce the warm sea surface temperatures reconstructed in the North Atlantic. Using a reconstruction of mid‐Piacenzian paleogeography that has the Bering Strait and Canadian Arctic Archipelago Straits closed, however, improves the simulation of the proxy‐indicated warm sea surface temperatures in the North Atlantic in the Community Climate System Model. We find that the closure of these small Arctic gateways strengthens the Atlantic Meridional Overturning Circulation, by inhibiting freshwater transport from the Pacific to the Arctic Ocean and from the Arctic Ocean to the Labrador Sea, leading to warmer sea surface temperatures in the North Atlantic. This indicates that the state of the Arctic gateways may influence the sensitivity of the North Atlantic climate in complex ways, and better understanding of the state of these Arctic gateways for past time periods is needed.

Influence of Model Bias on Simulating North Atlantic Sea Surface Temperature During the Mid‐Pliocene

“…In contrast, the SSS decreases in the Greenland‐Iceland‐Norwegian (GIN) seas owing to the weakened salinity transport (not shown). This is consistent with the CCSM4 modeling results by Otto‐Bliesner et al (). The flux‐corrected model (FWC), on the other hand, only simulates increased salinity in the western North Atlantic, in the Labrador Sea and west of Greenland (including the Baffin Bay; Figure b).…”

Contributions of aerosol‐cloud interactions to mid‐Piacenzian seasonally sea ice‐free Arctic Ocean

“…Half of the ESMs also feature perennial Arctic sea ice condition even including the ones with higher skills at simulating historical Arctic sea ice extent (Howell, Haywood, Otto‐Bliesner, et al, ). This apparent model‐proxy data mismatch cannot be fully resolved by orbital‐forcing driven millennial scale climate variability (Feng et al, ; Prescott et al, ; Salzmann et al, ), uncertainty in CO 2 estimates (Feng et al, ; Howell, Haywood, Dowsett, et al, ; Salzmann et al, ), changes in Arctic Ocean gateway configuration (Feng et al, ; Otto‐Bliesner et al, ), or other changes in paleogeography and bathymetry (Hill, ; Robinson et al, ).…”

Expanding Greenland Ice Sheet Enhances Sensitivity of Plio‐Pleistocene Climate to Obliquity Forcing in the Kiel Climate Model

“…The SST cooling following the buildup of the GrIS is rather weak compared to the SST change estimated from North Atlantic Sites ODP 982 (Figure S1a) and Deep Sea Drilling Project (DSDP) 607 of about 3 K (Lawrence et al, ). This suggests the importance of additional drivers during the Plio‐Pleistocene transition such as the closure and opening of Bering and Canadian Archipelago Straits, and the emergence of the modern West and East Antarctic Ice Sheet (Brierley & Fedorov, ; Hill et al, ; Otto‐Bliesner et al, ). The opening of both Bering and the Canadian Archipelago Straits is linked to a 1.3 K SST cooling in the North Atlantic (Otto‐Bliesner et al, ), while the glaciation over West and East Antarctic supports a deep ocean cooling of 2.0 K reconstructed at Site DSDP 607 (Hill et al, ).…”

“…This suggests the importance of additional drivers during the Plio‐Pleistocene transition such as the closure and opening of Bering and Canadian Archipelago Straits, and the emergence of the modern West and East Antarctic Ice Sheet (Brierley & Fedorov, ; Hill et al, ; Otto‐Bliesner et al, ). The opening of both Bering and the Canadian Archipelago Straits is linked to a 1.3 K SST cooling in the North Atlantic (Otto‐Bliesner et al, ), while the glaciation over West and East Antarctic supports a deep ocean cooling of 2.0 K reconstructed at Site DSDP 607 (Hill et al, ). The model‐data discrepancy in this study would likely be smaller if these changes in land surface and land sea distribution were included in the simulations.…”

“…The influence of the ice sheets over North America and Europe (Bintanja & Van de Wal, 2008) is not accounted for in our experiments with the KCM. Additionally, the opening of Arctic oceanic gateways and ice sheets over West and East Antarctic is not considered and may further weaken the interhemispheric temperature gradient (Brierley & Fedorov, 2016;Hill et al, 2017;Otto-Bliesner et al, 2017). Knies et al (2014) suggested the gradual emergence of modern Arctic sea ice, which may also provide a freshwater forcing on the AMOC.…”