Pliocene Arctic Climate Teleconnections

The main goal of INDNOR-PACT "Pliocene Arctic Teleconnection" was to study climate variability in the Arctic Ocean through Pliocene epoch from ~5.3 to 2.7 million years ago with focus on the Mid-Pliocene Warmth between 3.2 and 3.0 million years. It has been recognized that polar amplification of climate change and the drastic changes in Arctic sea ice cover has significant influence on the strength of the monsoon wind system and thus precipitation in India. The catastrophic floods and landslides in the Kahala province in southern India in summer 2016 summer was potentially a consequence of rapid atmospheric and oceanic circulation changes as a result of climate changes in the Arctic. It has been postulated that during the Mid-Pliocene Warmth, the Arctic Ocean was completely ice free. PACT has tested this hypothesis and wanted to study whether an ice-free Arctic Ocean had any impact on the monsoon system during the Mid-Pliocene. 2 Implementation and results. We had three main goals in the project: (1) More complete knowledge of mid-Pliocene sea ice variability and sea-surface temperature changes: We reached this goal by a combined effort of the Norwegian-Indian PACT team supported by our UK colleagues from Plymouth and Leeds and published a milestone paper in the journal Earth and Planetary Science Letters (EPSL) lead by the early career PACT scientist Waliur Rahaman (see list of publication). (2) Improved understanding of large-scale teleconnection between the Arctic Ocean the Asian/Australian monsoon system during the Mid-Pliocene Warmth through upcoming discoveries during IODP Expeditions 355/356 from PACT scientific members from India and Norway: Our female PACT post doc (Soma Baranwal) and senior scientist Manish Tiwari (NCAOR, Goa India) joined the IODP Expeditions 355/356 in the Indian Ocean and contributed to the new discoveries made from this material (see publication list). (3) A more robust quantitative reconstruction of the most recent warm climatic state with near current CO2 levels through incorporation of new Arctic model boundary conditions: Here, we have not reached our goal yet. We tested the climate model results provided by our partners at Leeds University with our empirical results from borehole analyses and concluded that the new interpretation from boreholes requires implementation of improved boundary conditions for the Arctic climate warmth during the Pliocene Warm Period in the models. This is currently been implemented, but no concrete results can be presented yet.

Impact/Social benefit and user relevance: We believe that our finding of a summer sea ice free Arctic Ocean triggered by the Atlantification of the Arctic Ocean during the Pliocene Warm Period is a breakthrough for an improved understanding for future scenarios in the light of ongoing polar amplification of global warming. The modelling community is aware about this new finding and adjustments of climate models for improved boundary conditions for future climate scenario in the Arctic are currently implemented. The improvement of climate models based on better empirical constraints for Arctic warm climates in the past through PACT is essentially important to better predict sea ice development for the next decades which is important for ongoing business discussion on increased ship transport through the Arctic and adjustments of fishery industries in Norwegian Arctic territories.

The PACT project provides research, training, and networking opportunities for an excellent cluster of Indo-Norwegian researchers teamed-up with leading scientists in Arctic sea ice variability and Pliocene climate modelling who will use the latest research tools in proxy-based reconstruction and numerical modeling of climate change with the aim of improving our understanding of Mid-Pliocene Warmth in the Arctic and its teleconnection to Monsoon variability in the Indian Ocean. This will improve our understanding of how world ocean and atmospheric circulation patterns generate and/or maintain Mid-Pliocene warmth and provides a robust and more quantitative projection of the variability and complexity of the climate system in polar regions for the future where the Earth is expected to be warmer. PACT includes multi- and interdisciplinary scientific exchange, secondments at Indian and Norwegian research institutions, a publication and dissemination plan as well as exposure to a large international network of collaborators (IODP, International Ocean Discovery Program) through active participation of two PACT members on Expedition 355 and 356 to the Indian Ocean in 2015.