Assessment of Increasing Open Water Leads Along Northern Ellesmere Island with Satellite Imagery and Digital Ice Charts Miriam Richer McCallum, Department of Geography, University of Ottawa, Ottawa, Ontario Dr. Luke Copland, Department of Geography, University of Ottawa, Ottawa, Ontario Dr. Derek Mueller, Department of Geography and Environmental Studies, Carleton University, Ottawa, Ontario.

Introduction Arctic sea ice extent at the end of the summer melt season declined at a rate of 10.1% decade-1 from 1996 to 2007, and 12.4% decade-1 from 2008 to 2010 [1]. Satellite imagery has also revealed that the open water area in the Arctic Basin north of 65oN has been increasing at the rate of 23% decade-1 [2]. At times over the past several summers, large, long-lived leads have occurred at the northern coast of Ellesmere Island [3]. It is not known how unusual these leads are in a historical context or whether this trend will continue into the future. The objective of this study is to analyze satellite imagery and ice charts along this coast to determine if the extent and timing of open water has changed over time, and if so, what factors are contributing to this.

Methodology

MODIS remote sensing imagery [4] from 2002 onwards is used to examine the extent of open water along the northern coast of Ellesmere Island from Alert to Nansen Sound (Figure 1A). Sea ice charts from the Canadian Ice Service [5] were also assessed to evaluate sea ice conditions from 1997 to 2011 (Figures 1B & 1C). These images were only examined during the summer. Vector polygons from these ice charts were separated into three categories according to sea ice concentration: Open/Bergy Water (<1/10 concentration); Very Open Drift (1/10 to 3/10 concentration); and Open Drift (4/10 to 6/10 concentration) (Figure 1D). Both the images and ice chart data were used to determine the time of the year that these leads were present and for what duration, along with their size and shape.

The occurrence of leads was related to daily surface air temperatures and winds derived from NCEP/NCAR Reanalysis [6], as well as the annual minimum sea ice extent (NSIDC : http://nsidc.org/arcticseaicenews/)[7].

Results & Discussion Open water leads have been observed along northern Ellesmere Island every summer since 1999, with the exception of 2006. Due to a lack of available data prior to 1997, it is not known how unusual the appearance of these leads is or whether this trend will continue into the future. The majority of leads were observed during the month of August, although recently leads have been forming earlier in the summer and lasting for longer periods (e.g.,. from July through September in 2008 and 2011). The earliest onset of leads was during the month of June in 2010. Figure 2A indicates that leads observed throughout the study period do not indicate an overall long-term increase of open water, although in several recent there have been large, long-duration leads (Figure 2B). However, there have been significant ice shelf calving events from the areas adjacent to the leads during periods of open water conditions. There were two major factors that favoured the formation of a shore-lead (Table 1), namely offshore winds (Figure 2C) and a large number of melting degree days (Figure 2D).

Figure 2 A) Total weekly observation of open water leads according to CISDA (Open/Bergy Water, Very Open Drift & Open Drift); B) Open water index from 1997 to 2011, acquired from the CISDA (Open/Bergy Water, Very Open Drift & Open Drift); C) Wind magnitude and direction along with weekly open water leads from 1997 to 2011, acquired from the NCEP/NCER Reanalysis ; D) Monthly (JJAS) FDD and MDD from 1997 to 2001, acquired from the NCEP/NCAR Reanalysis

Jul 01 Jul 06 Jul 15 Jul 22 Jul 29 Aug 05 Aug 12 Aug 19 Aug 26 Sep 02 Sep 09 Sep 16

1997

1998

1999

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

References [1] Stroeve et al. 2007-2011 Geophys Res Lett 34:L09501 & DOI 10.1007/s10584-011-0101-1; [2] England et al. 2008 Geophys Res Lett 35:L19502; [3] Copland et al. 2007 Geophys Res Lett 34:L21501; [4] MODIS, Rapid Response System: http://earthdata.nasa.gov/data/near-real-time-data/rapid-response; [5] CIS: http://ice-glaces.ec.gc.ca/; [6] NCEP/NCAR Reanalysis: http://www.esrl.noaa.gov/psd/data/reanalysis/reanalysis.shtml ; [7] NSIDC : http://nsidc.org/arcticseaicenews/; [8] Deser, C., Walsh, J. E., & Timlin, M. S. (2000). Arctic sea ice variability in the context of recent atmospheric circulation trends. Journal of Climate, 13(3), 617-633; [9] Howell, S. E. L., Tivy, A., Agnew, T., Markus, T., & Derksen, C. (2010). Extreme low sea ice years in the canadian arctic archipelago: 1998 versus 2007. Journal of Geophysical Research C: Oceans, 115(10); [10] Stroeve, J.C., Serreze, M.C., Holland, M.M., Kay, J.E., Malanik, J., & Barrett, A.P. (2001) The Arctic’s rapidly shrinking sea ice cover: a research synthesis. Climate Change. DOI 10.1007/s10584-011-0101-1 ; [11] Stroeve, J.C., Holland, M. M., Meier, W., Scambos, T., & Serreze, M. (2007). Arctic sea ice decline: Faster than forecast. Geophysical Research Letters, 34(9)

Figure 1 A) Location of the study area (in black box); B) Polygon shapefile showing open water on July 28, 2008. The base map is a MODIS image; C) Open water on August 29, 2011; D) Diagram of ice concentrations (MANICE, 2007)

August 17, 2008

August 27, 2008 September 2, 2008

August 6, 2008

August 12, 2008

0 50 100 150 20025Kilometers

³July 30, 2008

August 2, 2005 ³0 50 100 150 20025

Kilometers

August 15, 2005

August 1, 2005

August 16, 2005

August 14, 2005

August 17, 2005

Average Length

(km) Width range

(km) Duration (days)

1997 - - -

1998 - - -

1999 283 5 to 39 -

2000 35 29 -

2001 239 3 to 19 -

2002 418 1 to 45 21

2003 148 3 to 17 9

2004 85 2 to 9 10

2005 313 1 to 27 20 2006 - - -

2007 429 3 to 48 27

2008 482 2 to 92 78

2009 334 4 to 30 15

2010 287 2 to 35 17

2011 350 1 to 44 38

Table 1 Average length and width range of open water leads as well as their duration (derived from MODIS imagery)

Figure 3 A) Time series of Open Water lead in front in 2005 derived from MODIS satellite imagery (red circle indicates the Ayles Ice Island, yellow indicates loss of MLSI in Yelverton Bay); B) Time series of Open Water lead in 2008 (red circle indicates the loss of the Serson Ice Shelf, yellow the collapse of the Markham Ice Shelf)

Conclusions It has already been explained by several authors that sea ice is influenced by long term temperature changes and strong winds [8-11]. These factors appear to explain why these leads have been occurring and how they have been a large influence on the most recent ice shelf calving events (Figure 3A, 3B). The persistence of open water leads along the coast-line has the potential to enhance further sea ice losses in this region due to the reduction in surface albedo and consequent ocean warming. This concern only raises more questions about the long-term survival of thick multiyear sea ice and the remaining ice shelves along northern Ellesmere Island.

0 340 680 1,020 1,360170Kilometers

¯