Baffin Bay is a small marginal basin between Greenland and the Canadian Arctic (Figure 1a). It is approximately 550 km east-west and 1,400 km north-south, with broad shelves on the Greenland side and a deep central region (Tang et al., 2004). Based on two distinct periods of mooring observations in 2003-2006 and 2007-2009, net southward fluxes from the Arctic Ocean through Nares Strait were 0.71 0.09  and 1 03 0 11 . .

The intrusion of the warm and saline Atlantic Water (AW) has significant implications and feedback on the dynamics and thermodynamics of the Arctic Ocean. The AW enters the Arctic Ocean through two gateways: Fram Strait (FS) and the Barents Sea Opening (BSO). The AW is the dominant source of oceanic heat to the Arctic Ocean. In conjunction with the measurements in key hydrographic sections, numerical ocean modeling provides us with a useful tool to characterize and corroborate the temporal and spatial variability of the AW branches. Simulations are conducted using the regional configuration Arctic and North Hemispheric Atlantic (ANHA) of the ocean/sea‐ice model Nucleus for Modeling of the Ocean running at 1/4° and 1/12° resolution. Online passive tracers from the model configuration are used to trace the pathways of the AW inflow in the Arctic Ocean. While studying the variability of the AW through FS and the BSO, a cold mode of AW (Cold Atlantic Water [CAW]) with a temperature below 0℃ is detected along the rim of the eastern Eurasian Basin. It is formed primarily due to the intense sea surface cooling of the AW in the Barents and Kara Seas. The CAW exhibits the cascading process as it propagates downstream through the St. Anna Trough, leading to a considerable mixing with the ambient water. The CAW pulses eventually result in a significant heat content reduction in the eastern Arctic. This study provides insight into the changing AW property and its potential impact on the Arctic Basin.

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PAN-EURASIAN EXPERIMENT (PEEX) PROGRAM-TOWARDS ARCTIC-BOREAL SYSTEM UNDERSTANDING Pan-Eurasian Experiment (PEEX) program (https://www.atm.helsinki.fi/peex/) is an international, multidisciplinary, multiscale and multidimensional bottom up initiative established in 2012. The initiative has grown fast and currently it involves research communities from 25 different countries with a network of approximately 2000 researchers from Europe, Russia and China. The focus of the PEEX initiative is to solve interlinked global environmental challenges influencing societies in the Northern Eurasian region, specifically in the Arctic-boreal regions and the Arctic Ocean, which are located at latitudes higher than 45°N. These areas are expected to undergo substantial changes during the next decades (IPCC, 2014). The importance of the Northern regions even in a global point of view is foreseen to increase not only because of the climate change, but also due to globalization, shipping, demography and utilization of natural resources. The Arctic-boreal Northern Eurasian region, and especially the arctic coastal lines and Siberian region of the Russian territory, are extremely crucial for and sensitive to the global climate. Permafrost thawing together with the Arctic sea ice changes will have multiple environmental (greenhouse gas emissions, air quality), economic (energy production, use of mineral, traffic and shipping and infrastructures) and societal (urbanization, cultural changes) consequences, which are intricately interconnected with each other. In the PEEX approach the climate change is key driver in the dynamics of the land, atmosphere, aquatic and societal systems. The system-based structure of PEEX introduces altogether twelve thematic research areas. The approach will piece-by-piece develop into a holistic system understanding, which the PEEX community and stakeholders can quantify the most dominant feedbacks and interactions between the components within the system providing novel understanding in the dynamics of Arctic-boreal biogeochemical cycles of e.g. water, carbon, nitrogen