The 42 m ICOS tower at Hurdal



Figure 1: The 42 m ICOS tower at Hurdal. Photo: Holger Lange, NIBIO.

The terrestrial component of ICOS Norway aims at monitoring the GHG (Greenhouse Gas) balance of key Norwegian land ecosystems and at understanding their response to climate change, variability and extreme events. Up to now, we concentrate our efforts on forest ecosystems, which currently sequester carbon in excess of 25 Mton CO2 per year. This value is equivalent to half the total reported GHG emissions for the country, underscoring the need to better understanding the dynamics of carbon sequestration in Norwegian forest and its sensitivity to climate change.

So far, the terrestrial component is represented by an ICOS class 2 station located in Southeast Norway in the community of Hurdal, Viken county. The station (tower coordinates 60.371678 N, 11.079382 E) is operated by Norwegian Institute for Bioeconomy Researh (NIBIO), it is located in a mature Norway spruce forest stand and directly benefits from other monitoring programs: the Norwegian Institute of Air Research (NILU) has a 25 m tower at the site, around 100 m northwest of the ICOS tower, where air quality and atmospheric deposition are being measured since 1996, with data contributing to the EMEP and ACTRIS projects. In addition, the site is monitored since 1996 as an ICP-Forests level II plot by NIBIO, with regular measurements of soil water chemistry, throughfall, tree variables, and others. The tower (Fig. 1) is 42 m high, easily accessible by a forest road and inside a ca. 95 year old (in 2022) homogeneous forest stand (Fig. 2). The trees have an average height of 23 m, with a maximum of 25 m, and the site is of medium productivity (G17 in the Norwegian system). The station is being equipped with eddy-covariance (EC) instruments fully compatible with ICOS requirements. EC flux measurements commenced in September 2021 and are daily submitted to the ICOS Carbon Portal.  As of December 2022, the official labelling as a class 2 site is pending. 

The tower at Hurdal: view from a drone flight

Figure 2: The ICOS tower at Hurdal as seen during a drone flight (September 2021) with the surrounding forest. Direction view is towards northeast. Photo and drone operation: Junbin Zhao, NIBIO.