Connecting the Tropics to the Polar Regions
Description:
Dramatic climate change is affecting both the Arctic and West Antarctica, yet the relative roles of local versus remote forcings in causing the changes are being debated. As global climate change continues to unfold, the two-way links between the tropics and the poles will play key determining factors in the climatic evolution of these sensitive regions. Thus, the time is ripe for a detailed look at how the tropics and the poles are coupled climatically. This special collection of the Journal of Climate on “Connecting the Tropics to Polar Regions” grew out of a mini-conference on the same topic that was held at Lamont-Doherty Earth Observatory in June 2014: http://www.ldgo.columbia.edu/~xyuan/Mini-Conference/Web.html.
Subsequently, contributions were solicited from conference participants as well as colleagues worldwide with prior publications dealing with tropical-polar connections. Primarily, the manuscripts evaluate the remote impacts of various tropical forcings (El Nino–Southern Oscillation, Madden-Julian Oscillation, etc.) on polar and midlatitude atmospheric variability in the contemporary environment, and the Southern Hemisphere is emphasized.
Collection organizers:
David H. Bromwich, Byrd Polar & Climate Research Center, The Ohio State University
Xiaojun Yuan, Lamont-Doherty Earth Observatory, Columbia University
Connecting the Tropics to the Polar Regions
Abstract
This study explores the impact of the Indian Ocean dipole (IOD) on the Southern Hemisphere sea ice variability. Singular value decomposition (SVD) of September–November sea ice concentration and sea surface temperature (SST) anomalies reveals patterns of El Niño–Southern Oscillation (ENSO) in the Pacific and the IOD in the equatorial Indian Ocean. The relative importance of the IOD’s impact on sea ice in the Pacific sector of Antarctica is difficult to assess for two reasons: 1) ENSO generates larger anomalies in the Pacific and Weddell Sea and 2) many of the positive (negative) IODs co-occur with El Niño (La Niña). West of the Ross Sea, sea ice growth can be attributed to the negative heat fluxes associated with cold meridional flow between high and low pressure cells generated by the effects of the IOD. However, the locations of these positive and negative pressure anomaly centers tend to appear north of the sea ice zone during combined ENSO–IOD events, reducing the influence of the IOD on sea ice. The IOD influence is at a maximum in the region west of the Ross Sea. When ENSO is removed, sea ice in the Indian Ocean (near 60°E) increases because of cold outflows west of low pressure centers while sea ice near 90°E decreases because of the warm advection west of a high pressure center located south of Australia.
Abstract
This study explores the impact of the Indian Ocean dipole (IOD) on the Southern Hemisphere sea ice variability. Singular value decomposition (SVD) of September–November sea ice concentration and sea surface temperature (SST) anomalies reveals patterns of El Niño–Southern Oscillation (ENSO) in the Pacific and the IOD in the equatorial Indian Ocean. The relative importance of the IOD’s impact on sea ice in the Pacific sector of Antarctica is difficult to assess for two reasons: 1) ENSO generates larger anomalies in the Pacific and Weddell Sea and 2) many of the positive (negative) IODs co-occur with El Niño (La Niña). West of the Ross Sea, sea ice growth can be attributed to the negative heat fluxes associated with cold meridional flow between high and low pressure cells generated by the effects of the IOD. However, the locations of these positive and negative pressure anomaly centers tend to appear north of the sea ice zone during combined ENSO–IOD events, reducing the influence of the IOD on sea ice. The IOD influence is at a maximum in the region west of the Ross Sea. When ENSO is removed, sea ice in the Indian Ocean (near 60°E) increases because of cold outflows west of low pressure centers while sea ice near 90°E decreases because of the warm advection west of a high pressure center located south of Australia.
