The freshwater content of the Arctic Ocean is increasing as the Earth’s climate warms. Chemical analysis indicates that the source is both melting ice and the Pacific Ocean.
May 17, 2011
May 16: The weather has been great over the past couple of days since our last post, and we could get more samples — 15 stations so far. Today is an exception, with the whole region covered in fog; one can barely see 10 feet away.
Now that we have showed you the way we get samples, we will try to explain what the analysis of the water tells us about the Arctic Ocean and its link to climate change.
One aspect of our research is to understand how the freshwater content of the Arctic Ocean is changing as the Earth’s climate warms. There are three major sources of freshwater in the Arctic Ocean:
1) Meteoric water, which is water input from the atmosphere as rain or snow; most of this water enters the Arctic Ocean from rivers.
2) Freshwater that is mixed with North Pacific water and enters the Arctic Ocean through the Bering Strait.
3) Melting of sea ice.
Using a combination of all the results of our sample analysis, which consists of chemical measurements and tracer analysis, we are able to determine the fractions of these three freshwater sources in a water sample.
Some of the results are shown in these maps. The distribution of the total freshwater present in 2008 and 2009 are shown in Fig. 1. The data used to produce these maps are from our study, including data from our University of Washington colleagues, Mike Steele, Wendy Ermold, and Roger Anderson, and from two other research programs, The North Pole Environmental Observatory and the ice-tethered profiler program. Comparison of these two maps reveals the water north of Ellesmere Island and Greenland becoming fresher (red indicates high freshwater content, blue low freshwater content.
Notably, while the water of the Arctic Ocean became fresher, the amount of meteoric water (mainly river runoff) indicates roughly the same amount in our study area in both years (Fig. 2). Maps of sea ice melt water shows an increase between 2008 and 2009 (Fig. 3) as well as freshwater from the North Pacific Ocean (not shown).
Thus the increase in freshwater content between 2008 and 2009 was caused by an increase in sea ice melt and freshwater from the Pacific Ocean. It is interesting to note that a large amount of sea ice melted in the summer of 2007, and the flow of this water through our study region may be the cause of the increase in sea ice melt-water.