Over the past decades, Arctic sea ice has declined in thickness and extent and is shifting towards a seasonal ice regime, with accelerated ice drift and an increase in the seasonal ice zone. The changing Arctic ice cover will impact the trans-border exchange of sea ice between the Exclusive Economic Zones (EEZs) of the Arctic nations, with important implications for ice-rafted contaminant transport. To investigate projected changes to transnational ice exchange, we use the Lagrangian Ice Tracking System (LITS) to follow ice floes from the location of their formation to where they ultimately melt. We apply this tool to output from two ensembles of the Community Earth System Model (CESM): the CESM Large Ensemble, which uses a high emission scenario (RCP8.5) that leads to over 4°C global warming by 2100, and the CESM Low Warming ensemble, with reduced emissions that lead to a stabilized warming of 2°C by 2060. We also use the National Snow and Ice Data Center Polar Pathfinder and Climate Data Record products to evaluate the fidelity of the CESM present-day tracking simulations. Transnational ice exchange is well represented in CESM except for ice traveling from Russia to Norway, with twice as much ice following this pathway compared to observations. Initial results suggest this might be due to a combination of internal variability and speed biases in the observational data. The CESM projects that by mid-century, transnational ice exchange will expand, with a large increase in the fraction of transnational ice originating from Russia and the Central Arctic. As the seasonal ice zone grows, ice floes accelerate and transit times decrease, eventually cutting off ice exchange between longer pathways. By the end of the 21st century, we see a large impact of the emission scenario on ice exchange: consistent ice-free summers under the high emission scenario act to reduce the total fraction of transnational ice exchange compared to mid-century. The low emission scenario on the other hand continues to see an increase in transnational ice exchange by 2100. Under both scenarios, all pathways have decreased to average transit times of less than 2 years, compared to a maximum of 6 years under present-day conditions and 3 years by mid-century, effectively bringing the Arctic nations closer together.

What controls the distribution of barium (Ba) in the oceans? Answers to this question have been sought since early studies revealed relationships between particulate Ba (pBa) and POC and dissolved Ba (dBa) and silicate, suggesting applications for Ba as a paleoproductivity tracer and as a tracer of modern ocean circulation. Herein, we investigated the Arctic Ocean Ba cycle through a one-of-a-kind data set containing dissolved (dBa), particulate (pBa), and stable isotope Ba (δ138Ba) data from four Arctic GEOTRACES expeditions conducted in 2015. We hypothesized that margins would be a substantial source of Ba to the Arctic Ocean water column. The dBa, pBa, and δ138Ba distributions all suggest significant modification of inflowing Pacific seawater over the shelves, and the dBa mass balance implies that ~50% of the dBa inventory (upper 500 m of the Arctic water column) is not supplied by conservatively advected inputs. Calculated areal dBa fluxes are up to 10 µmol m-2 d-1 on the margin, which is comparable to fluxes described in other regions. Applying this approach to dBa data from the 1994 Arctic Ocean Survey yields similar results. Surprisingly, the Canadian Arctic Archipelago did not appear to have a similar margin source; rather, the dBa distribution in this section is consistent with mixing of Arctic Ocean-derived waters and Baffin-bay derived waters. Although we lack enough information to identify the specifics of the shelf sediment Ba source, we suspect that a terrigenous source (e.g., submarine groundwater discharge or fluvial particles) is an important contributor

For youth with limited role models in the STEM fields, and restricted summer research opportunities resulting from a lack of financial resources and academic connections, the opportunity to participate in academically connected, community based science research programs can be incredibly empowering. Providing these opportunities is critically important but it takes purposeful work, persistent outreach and strong community networks. We note that while providing these opportunities is incredibly rewarding, but there is a lot of work both up front and ongoing. This work is itself rewarding when networks are humming and enthusiasm for involvement is high, but it can be challenging when ceilings are hit and walls seem to arise unexpectedly. “Early Engagement in Research: Broadening participation through engagement in authentic science research” builds a regional network of summer research experiences for high school students underrepresented in STEM, starting from a successful model that has provided high school summer field research opportunities for New York City youth for over a decade (Secondary School Field Research Program). The program is developed around regional partnerships between various combinations of academic institutions and research centers, community environmental and education centers, state cooperative extensions, high schools and school networks, state and local park systems and land management groups. Each location has a unique approach, but all include some similar attributes. Each tackles an authentic science research issue that affects the local community such as microbiology in the local streams and microplastics in the local bays and biology, and each includes peer and near peer mentoring for the students along with a scientist mentor. Encouraging professional development of each student is central to the program. Technical instruction includes the use of scientific instruments and equipment, data recording and interpretation. Professional discussions include how to successfully read and dissect a science journal article, how to create and present a science poster and most importantly how build a network for themselves in STEM, and how to help us work with them to support the diversity that is needed for all of science to be inclusive and ultimately meet the needs of our future.