Simulated Arctic Ocean Freshwater Budgets in the Twentieth and Twenty-First Centuries

Abstract

The Arctic Ocean freshwater budgets in climate model integrations of the twentieth and twenty-first century are examined. An ensemble of six members of the Community Climate System Model version 3 (CCSM3) is used for the analysis, allowing the anthropogenically forced trends over the integration length to be assessed. Mechanisms driving trends in the budgets are diagnosed, and the implications of changes in the Arctic-North Atlantic exchange on the Labrador Sea and Greenland-Iceland-Norwegian (GIN) Seas properties are discussed. Over the twentieth and the twenty-first centuries, the Arctic freshens as a result of increased river runoff, net precipitation, and decreased ice growth. For many of the budget terms, the maximum 50-yr trends in the time series occur from approximately 1975 to 2025, suggesting that we are currently in the midst of large Arctic change. The total freshwater exchange between the Arctic and North Atlantic increases over the twentieth and twenty-first centuries with decreases in ice export more than compensated for by an increase in the liquid freshwater export. Changes in both the liquid and solid (ice) Fram Strait freshwater fluxes are transported southward by the East Greenland Current and partially removed from the GIN Seas. Nevertheless, reductions in GIN sea ice melt do result from the reduced Fram Strait transport and account for the largest term in the changing ocean surface freshwater fluxes in this region. This counteracts the increased ocean stability due to the warming climate and helps to maintain GIN sea deep-water formation.

Multiple Effects of Changes in Arctic Snow Cover

“…Holland et al 2006;Kattsov et al 2007). A warmer atmosphere carries more water vapour and with efficient precipitation-generating mechanisms (convergence and uplift), precipitation increases.…”

Chapter 1 Impacts of the Oceans on Climate Change

“…If the present rate of reduction in sea-ice continues, some models project an ice-free ocean in the Arctic summer by 2030 86 Philip C. Reid et al or 2040 (Holland et al, 2006) compared to the more conservative estimates of a loss of greater than 40% in the area covered by sea-ice by 2050 as suggested by the majority of IPCC AR4 models (Overland and Wang, 2007). A more recent modelling analysis of trends in ice extent, thickness and volume ; Whelan et al (2007) estimated that the Arctic may be ice free in the summer as early as 2013; however, more recent studies suggest a date of 2037 (Kerr, 2009).…”

Seasonal and hydrologic drivers of dissolved organic matter and nutrients in the upper Kuparuk River, Alaskan Arctic

“…For example, river discharge to the Arctic Ocean has increased (Peterson et al 2002;McClelland et al 2006), and climate models suggest that enhanced net precipitation over the pan-Arctic watershed under warmer conditions will support greater increases in continental runoff over the twenty-first century (Holland et al 2006Meehl et al 2006;Francis et al 2009). Interannual variability, sparse precipitation datasets at high latitudes, and challenges associated with quantifying winter precipitation have made it difficult to diagnose the exact causes of changes in Arctic river discharge to date (Rawlins et al 2009).…”